[PATCH v8 00/17] remoteproc: Add support for detaching a remote processor

@@ -2347,10 +2347,8 @@ int rproc_del(struct rproc *rproc)
 	if (!rproc)
 		return -EINVAL;
 
-	/* if rproc is marked always-on, rproc_add() booted it */
 	/* TODO: make sure this works with rproc->power > 1 */
-	if (rproc->auto_boot)
-		rproc_shutdown(rproc);
+	rproc_shutdown(rproc);
 
 	mutex_lock(&rproc->lock);
 	rproc->state = RPROC_DELETED;

@@ -1416,7 +1416,7 @@ static int rproc_start(struct rproc *rproc, const struct firmware *fw)
 	return ret;
 }
 
-static int rproc_attach(struct rproc *rproc)
+static int __rproc_attach(struct rproc *rproc)
 {
 	struct device *dev = &rproc->dev;
 	int ret;

@@ -1541,7 +1541,7 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
  * Attach to remote processor - similar to rproc_fw_boot() but without
  * the steps that deal with the firmware image.
  */
-static int rproc_actuate(struct rproc *rproc)
+static int rproc_attach(struct rproc *rproc)
 {
 	struct device *dev = &rproc->dev;
 	int ret;

@@ -1581,7 +1581,7 @@ static int rproc_actuate(struct rproc *rproc)
 		goto clean_up_resources;
 	}
 
-	ret = rproc_attach(rproc);
+	ret = __rproc_attach(rproc);
 	if (ret)
 		goto clean_up_resources;
 

@@ -1802,7 +1802,7 @@ int rproc_boot(struct rproc *rproc)
 	if (rproc->state == RPROC_DETACHED) {
 		dev_info(dev, "attaching to %s\n", rproc->name);
 
-		ret = rproc_actuate(rproc);
+		ret = rproc_attach(rproc);
 	} else {
 		dev_info(dev, "powering up %s\n", rproc->name);
 

@@ -172,6 +172,7 @@ static const char * const rproc_state_string[] = {
 	[RPROC_RUNNING]		= "running",
 	[RPROC_CRASHED]		= "crashed",
 	[RPROC_DELETED]		= "deleted",
+	[RPROC_ATTACHED]	= "attached",
 	[RPROC_DETACHED]	= "detached",
 	[RPROC_LAST]		= "invalid",
 };

@@ -405,6 +405,8 @@ struct rproc_ops {
  * @RPROC_RUNNING:	device is up and running
  * @RPROC_CRASHED:	device has crashed; need to start recovery
  * @RPROC_DELETED:	device is deleted
+ * @RPROC_ATTACHED:	device has been booted by another entity and the core
+ *			has attached to it
  * @RPROC_DETACHED:	device has been booted by another entity and waiting
  *			for the core to attach to it
  * @RPROC_LAST:		just keep this one at the end

@@ -421,8 +423,9 @@ enum rproc_state {
 	RPROC_RUNNING	= 2,
 	RPROC_CRASHED	= 3,
 	RPROC_DELETED	= 4,
-	RPROC_DETACHED	= 5,
-	RPROC_LAST	= 6,
+	RPROC_ATTACHED	= 5,
+	RPROC_DETACHED	= 6,
+	RPROC_LAST	= 7,
 };
 
 /**

@@ -546,6 +546,73 @@ static void stm32_rproc_kick(struct rproc *rproc, int vqid)
 	}
 }
 
+static int stm32_rproc_da_to_pa(struct rproc *rproc,
+				u64 da, phys_addr_t *pa)
+{
+	struct stm32_rproc *ddata = rproc->priv;
+	struct device *dev = rproc->dev.parent;
+	struct stm32_rproc_mem *p_mem;
+	unsigned int i;
+
+	for (i = 0; i < ddata->nb_rmems; i++) {
+		p_mem = &ddata->rmems[i];
+
+		if (da < p_mem->dev_addr ||
+		    da >= p_mem->dev_addr + p_mem->size)
+			continue;
+
+		*pa = da - p_mem->dev_addr + p_mem->bus_addr;
+		dev_dbg(dev, "da %llx to pa %#x\n", da, *pa);
+
+		return 0;
+	}
+
+	dev_err(dev, "can't translate da %llx\n", da);
+
+	return -EINVAL;
+}
+
+static struct resource_table *
+stm32_rproc_get_loaded_rsc_table(struct rproc *rproc, size_t *table_sz)
+{
+	struct stm32_rproc *ddata = rproc->priv;
+	struct device *dev = rproc->dev.parent;
+	phys_addr_t rsc_pa;
+	u32 rsc_da;
+	int err;
+
+	/* The resource table has already been mapped, nothing to do */
+	if (ddata->rsc_va)
+		goto done;
+
+	err = regmap_read(ddata->rsctbl.map, ddata->rsctbl.reg, &rsc_da);
+	if (err) {
+		dev_err(dev, "failed to read rsc tbl addr\n");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (!rsc_da)
+		/* no rsc table */
+		return ERR_PTR(-ENOENT);
+
+	err = stm32_rproc_da_to_pa(rproc, rsc_da, &rsc_pa);
+	if (err)
+		return ERR_PTR(err);
+
+	ddata->rsc_va = devm_ioremap_wc(dev, rsc_pa, RSC_TBL_SIZE);
+	if (IS_ERR_OR_NULL(ddata->rsc_va)) {
+		dev_err(dev, "Unable to map memory region: %pa+%zx\n",
+			&rsc_pa, RSC_TBL_SIZE);
+		ddata->rsc_va = NULL;
+		return ERR_PTR(-ENOMEM);
+	}
+
+done:
+	/* Assuming the resource table fits in 1kB is fair */
+	*table_sz = RSC_TBL_SIZE;
+	return (struct resource_table *)ddata->rsc_va;
+}
+
 static const struct rproc_ops st_rproc_ops = {
 	.start		= stm32_rproc_start,
 	.stop		= stm32_rproc_stop,

@@ -554,6 +621,7 @@ static const struct rproc_ops st_rproc_ops = {
 	.load		= rproc_elf_load_segments,
 	.parse_fw	= stm32_rproc_parse_fw,
 	.find_loaded_rsc_table = rproc_elf_find_loaded_rsc_table,
+	.get_loaded_rsc_table = stm32_rproc_get_loaded_rsc_table,
 	.sanity_check	= rproc_elf_sanity_check,
 	.get_boot_addr	= rproc_elf_get_boot_addr,
 };

@@ -695,75 +763,6 @@ static int stm32_rproc_get_m4_status(struct stm32_rproc *ddata,
 	return regmap_read(ddata->m4_state.map, ddata->m4_state.reg, state);
 }
 
-static int stm32_rproc_da_to_pa(struct platform_device *pdev,
-				struct stm32_rproc *ddata,
-				u64 da, phys_addr_t *pa)
-{
-	struct device *dev = &pdev->dev;
-	struct stm32_rproc_mem *p_mem;
-	unsigned int i;
-
-	for (i = 0; i < ddata->nb_rmems; i++) {
-		p_mem = &ddata->rmems[i];
-
-		if (da < p_mem->dev_addr ||
-		    da >= p_mem->dev_addr + p_mem->size)
-			continue;
-
-		*pa = da - p_mem->dev_addr + p_mem->bus_addr;
-		dev_dbg(dev, "da %llx to pa %#x\n", da, *pa);
-
-		return 0;
-	}
-
-	dev_err(dev, "can't translate da %llx\n", da);
-
-	return -EINVAL;
-}
-
-static int stm32_rproc_get_loaded_rsc_table(struct platform_device *pdev,
-					    struct rproc *rproc,
-					    struct stm32_rproc *ddata)
-{
-	struct device *dev = &pdev->dev;
-	phys_addr_t rsc_pa;
-	u32 rsc_da;
-	int err;
-
-	err = regmap_read(ddata->rsctbl.map, ddata->rsctbl.reg, &rsc_da);
-	if (err) {
-		dev_err(dev, "failed to read rsc tbl addr\n");
-		return err;
-	}
-
-	if (!rsc_da)
-		/* no rsc table */
-		return 0;
-
-	err = stm32_rproc_da_to_pa(pdev, ddata, rsc_da, &rsc_pa);
-	if (err)
-		return err;
-
-	ddata->rsc_va = devm_ioremap_wc(dev, rsc_pa, RSC_TBL_SIZE);
-	if (IS_ERR_OR_NULL(ddata->rsc_va)) {
-		dev_err(dev, "Unable to map memory region: %pa+%zx\n",
-			&rsc_pa, RSC_TBL_SIZE);
-		ddata->rsc_va = NULL;
-		return -ENOMEM;
-	}
-
-	/*
-	 * The resource table is already loaded in device memory, no need
-	 * to work with a cached table.
-	 */
-	rproc->cached_table = NULL;
-	/* Assuming the resource table fits in 1kB is fair */
-	rproc->table_sz = RSC_TBL_SIZE;
-	rproc->table_ptr = (struct resource_table *)ddata->rsc_va;
-
-	return 0;
-}
-
 static int stm32_rproc_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;

@@ -803,10 +802,6 @@ static int stm32_rproc_probe(struct platform_device *pdev)
 		ret = stm32_rproc_parse_memory_regions(rproc);
 		if (ret)
 			goto free_resources;
-
-		ret = stm32_rproc_get_loaded_rsc_table(pdev, rproc, ddata);
-		if (ret)
-			goto free_resources;
 	}
 
 	rproc->has_iommu = false;

@@ -1444,7 +1444,7 @@ static int __rproc_attach(struct rproc *rproc)
 		goto stop_rproc;
 	}
 
-	rproc->state = RPROC_RUNNING;
+	rproc->state = RPROC_ATTACHED;
 
 	dev_info(dev, "remote processor %s is now attached\n", rproc->name);
 

@@ -1659,14 +1659,6 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 
 	rproc->state = RPROC_OFFLINE;
 
-	/*
-	 * The remote processor has been stopped and is now offline, which means
-	 * that the next time it is brought back online the remoteproc core will
-	 * be responsible to load its firmware.  As such it is no longer
-	 * autonomous.
-	 */
-	rproc->autonomous = false;
-
 	dev_info(dev, "stopped remote processor %s\n", rproc->name);
 
 	return 0;

@@ -2077,16 +2069,6 @@ int rproc_add(struct rproc *rproc)
 	if (ret < 0)
 		return ret;
 
-	/*
-	 * Remind ourselves the remote processor has been attached to rather
-	 * than booted by the remoteproc core.  This is important because the
-	 * RPROC_DETACHED state will be lost as soon as the remote processor
-	 * has been attached to.  Used in firmware_show() and reset in
-	 * rproc_stop().
-	 */
-	if (rproc->state == RPROC_DETACHED)
-		rproc->autonomous = true;
-
 	/* if rproc is marked always-on, request it to boot */
 	if (rproc->auto_boot) {
 		ret = rproc_trigger_auto_boot(rproc);

@@ -138,11 +138,8 @@ static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
 	 * If the remote processor has been started by an external
 	 * entity we have no idea of what image it is running.  As such
 	 * simply display a generic string rather then rproc->firmware.
-	 *
-	 * Here we rely on the autonomous flag because a remote processor
-	 * may have been attached to and currently in a running state.
 	 */
-	if (rproc->autonomous)
+	if (rproc->state == RPROC_ATTACHED)
 		firmware = "unknown";
 
 	return sprintf(buf, "%s\n", firmware);

@@ -512,7 +512,6 @@ struct rproc_dump_segment {
  * @table_sz: size of @cached_table
  * @has_iommu: flag to indicate if remote processor is behind an MMU
  * @auto_boot: flag to indicate if remote processor should be auto-started
- * @autonomous: true if an external entity has booted the remote processor
  * @dump_segments: list of segments in the firmware
  * @nb_vdev: number of vdev currently handled by rproc
  * @char_dev: character device of the rproc

@@ -549,7 +548,6 @@ struct rproc {
 	size_t table_sz;
 	bool has_iommu;
 	bool auto_boot;
-	bool autonomous;
 	struct list_head dump_segments;
 	int nb_vdev;
 	u8 elf_class;

@@ -1706,6 +1706,36 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 	return 0;
 }
 
+/*
+ * __rproc_detach(): Does the opposite of __rproc_attach()
+ */
+static int __maybe_unused __rproc_detach(struct rproc *rproc)
+{
+	struct device *dev = &rproc->dev;
+	int ret;
+
+	/* No need to continue if a detach() operation has not been provided */
+	if (!rproc->ops->detach)
+		return -EINVAL;
+
+	/* Stop any subdevices for the remote processor */
+	rproc_stop_subdevices(rproc, false);
+
+	/* Tell the remote processor the core isn't available anymore */
+	ret = rproc->ops->detach(rproc);
+	if (ret) {
+		dev_err(dev, "can't detach from rproc: %d\n", ret);
+		return ret;
+	}
+
+	rproc_unprepare_subdevices(rproc);
+
+	rproc->state = RPROC_DETACHED;
+
+	dev_info(dev, "detached remote processor %s\n", rproc->name);
+
+	return 0;
+}
 
 /**
  * rproc_trigger_recovery() - recover a remoteproc

@@ -1582,10 +1582,17 @@ static int rproc_attach(struct rproc *rproc)
 		return ret;
 	}
 
+	/* Do anything that is needed to boot the remote processor */
+	ret = rproc_prepare_device(rproc);
+	if (ret) {
+		dev_err(dev, "can't prepare rproc %s: %d\n", rproc->name, ret);
+		goto disable_iommu;
+	}
+
 	ret = rproc_set_rsc_table(rproc);
 	if (ret) {
 		dev_err(dev, "can't load resource table: %d\n", ret);
-		goto disable_iommu;
+		goto unprepare_device;
 	}
 
 	/* reset max_notifyid */

@@ -1602,7 +1609,7 @@ static int rproc_attach(struct rproc *rproc)
 	ret = rproc_handle_resources(rproc, rproc_loading_handlers);
 	if (ret) {
 		dev_err(dev, "Failed to process resources: %d\n", ret);
-		goto disable_iommu;
+		goto unprepare_device;
 	}
 
 	/* Allocate carveout resources associated to rproc */

@@ -1621,6 +1628,9 @@ static int rproc_attach(struct rproc *rproc)
 
 clean_up_resources:
 	rproc_resource_cleanup(rproc);
+unprepare_device:
+	/* release HW resources if needed */
+	rproc_unprepare_device(rproc);
 disable_iommu:
 	rproc_disable_iommu(rproc);
 	return ret;

@@ -207,16 +207,7 @@ static int stm32_rproc_mbox_idx(struct rproc *rproc, const unsigned char *name)
 	return -EINVAL;
 }
 
-static int stm32_rproc_elf_load_rsc_table(struct rproc *rproc,
-					  const struct firmware *fw)
-{
-	if (rproc_elf_load_rsc_table(rproc, fw))
-		dev_warn(&rproc->dev, "no resource table found for this firmware\n");
-
-	return 0;
-}
-
-static int stm32_rproc_parse_memory_regions(struct rproc *rproc)
+static int stm32_rproc_prepare(struct rproc *rproc)
 {
 	struct device *dev = rproc->dev.parent;
 	struct device_node *np = dev->of_node;

@@ -274,12 +265,10 @@ static int stm32_rproc_parse_memory_regions(struct rproc *rproc)
 
 static int stm32_rproc_parse_fw(struct rproc *rproc, const struct firmware *fw)
 {
-	int ret = stm32_rproc_parse_memory_regions(rproc);
-
-	if (ret)
-		return ret;
+	if (rproc_elf_load_rsc_table(rproc, fw))
+		dev_warn(&rproc->dev, "no resource table found for this firmware\n");
 
-	return stm32_rproc_elf_load_rsc_table(rproc, fw);
+	return 0;
 }
 
 static irqreturn_t stm32_rproc_wdg(int irq, void *data)

@@ -614,6 +603,7 @@ stm32_rproc_get_loaded_rsc_table(struct rproc *rproc, size_t *table_sz)
 }
 
 static const struct rproc_ops st_rproc_ops = {
+	.prepare	= stm32_rproc_prepare,
 	.start		= stm32_rproc_start,
 	.stop		= stm32_rproc_stop,
 	.attach		= stm32_rproc_attach,

@@ -796,14 +786,9 @@ static int stm32_rproc_probe(struct platform_device *pdev)
 	if (ret)
 		goto free_rproc;
 
-	if (state == M4_STATE_CRUN) {
+	if (state == M4_STATE_CRUN)
 		rproc->state = RPROC_DETACHED;
 
-		ret = stm32_rproc_parse_memory_regions(rproc);
-		if (ret)
-			goto free_resources;
-	}
-
 	rproc->has_iommu = false;
 	ddata->workqueue = create_workqueue(dev_name(dev));
 	if (!ddata->workqueue) {

@@ -1537,6 +1537,32 @@ static int rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
 	return ret;
 }
 
+static int rproc_set_rsc_table(struct rproc *rproc)
+{
+	struct resource_table *table_ptr;
+	struct device *dev = &rproc->dev;
+	size_t table_sz;
+	int ret;
+
+	table_ptr = rproc_get_loaded_rsc_table(rproc, &table_sz);
+	if (!table_ptr) {
+		/* Not having a resource table is acceptable */
+		return 0;
+	}
+
+	if (IS_ERR(table_ptr)) {
+		ret = PTR_ERR(table_ptr);
+		dev_err(dev, "can't load resource table: %d\n", ret);
+		return ret;
+	}
+
+	rproc->cached_table = NULL;
+	rproc->table_ptr = table_ptr;
+	rproc->table_sz = table_sz;
+
+	return 0;
+}
+
 /*
  * Attach to remote processor - similar to rproc_fw_boot() but without
  * the steps that deal with the firmware image.

@@ -1556,6 +1582,12 @@ static int rproc_attach(struct rproc *rproc)
 		return ret;
 	}
 
+	ret = rproc_set_rsc_table(rproc);
+	if (ret) {
+		dev_err(dev, "can't load resource table: %d\n", ret);
+		goto disable_iommu;
+	}
+
 	/* reset max_notifyid */
 	rproc->max_notifyid = -1;
 

@@ -177,6 +177,16 @@ struct resource_table *rproc_find_loaded_rsc_table(struct rproc *rproc,
 	return NULL;
 }
 
+static inline
+struct resource_table *rproc_get_loaded_rsc_table(struct rproc *rproc,
+						  size_t *size)
+{
+	if (rproc->ops->get_loaded_rsc_table)
+		return rproc->ops->get_loaded_rsc_table(rproc, size);
+
+	return NULL;
+}
+
 static inline
 bool rproc_u64_fit_in_size_t(u64 val)
 {

@@ -368,7 +368,9 @@ enum rsc_handling_status {
  * RSC_HANDLED if resource was handled, RSC_IGNORED if not handled and a
  * negative value on error
  * @load_rsc_table:	load resource table from firmware image
- * @find_loaded_rsc_table: find the loaded resouce table
+ * @find_loaded_rsc_table: find the loaded resource table from firmware image
+ * @get_loaded_rsc_table: get resource table installed in memory
+ *			  by external entity
  * @load:		load firmware to memory, where the remote processor
  *			expects to find it
  * @sanity_check:	sanity check the fw image

@@ -390,6 +392,8 @@ struct rproc_ops {
 			  int offset, int avail);
 	struct resource_table *(*find_loaded_rsc_table)(
 				struct rproc *rproc, const struct firmware *fw);
+	struct resource_table *(*get_loaded_rsc_table)(
+				struct rproc *rproc, size_t *size);
 	int (*load)(struct rproc *rproc, const struct firmware *fw);
 	int (*sanity_check)(struct rproc *rproc, const struct firmware *fw);
 	u64 (*get_boot_addr)(struct rproc *rproc, const struct firmware *fw);

@@ -361,6 +361,7 @@ enum rsc_handling_status {
  * @start:	power on the device and boot it
  * @stop:	power off the device
  * @attach:	attach to a device that his already powered up
+ * @detach:	detach from a device, leaving it powered up
  * @kick:	kick a virtqueue (virtqueue id given as a parameter)
  * @da_to_va:	optional platform hook to perform address translations
  * @parse_fw:	parse firmware to extract information (e.g. resource table)

@@ -385,6 +386,7 @@ struct rproc_ops {
 	int (*start)(struct rproc *rproc);
 	int (*stop)(struct rproc *rproc);
 	int (*attach)(struct rproc *rproc);
+	int (*detach)(struct rproc *rproc);
 	void (*kick)(struct rproc *rproc, int vqid);
 	void * (*da_to_va)(struct rproc *rproc, u64 da, size_t len);
 	int (*parse_fw)(struct rproc *rproc, const struct firmware *fw);

@@ -1709,7 +1709,7 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 /*
  * __rproc_detach(): Does the opposite of __rproc_attach()
  */
-static int __maybe_unused __rproc_detach(struct rproc *rproc)
+static int __rproc_detach(struct rproc *rproc)
 {
 	struct device *dev = &rproc->dev;
 	int ret;

@@ -1948,6 +1948,62 @@ void rproc_shutdown(struct rproc *rproc)
 }
 EXPORT_SYMBOL(rproc_shutdown);
 
+/**
+ * rproc_detach() - Detach the remote processor from the
+ * remoteproc core
+ *
+ * @rproc: the remote processor
+ *
+ * Detach a remote processor (previously attached to with rproc_attach()).
+ *
+ * In case @rproc is still being used by an additional user(s), then
+ * this function will just decrement the power refcount and exit,
+ * without disconnecting the device.
+ *
+ * Function rproc_detach() calls __rproc_detach() in order to let a remote
+ * processor know that services provided by the application processor are
+ * no longer available.  From there it should be possible to remove the
+ * platform driver and even power cycle the application processor (if the HW
+ * supports it) without needing to switch off the remote processor.
+ */
+int rproc_detach(struct rproc *rproc)
+{
+	struct device *dev = &rproc->dev;
+	int ret;
+
+	ret = mutex_lock_interruptible(&rproc->lock);
+	if (ret) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, ret);
+		return ret;
+	}
+
+	/* if the remote proc is still needed, bail out */
+	if (!atomic_dec_and_test(&rproc->power)) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = __rproc_detach(rproc);
+	if (ret) {
+		atomic_inc(&rproc->power);
+		goto out;
+	}
+
+	/* clean up all acquired resources */
+	rproc_resource_cleanup(rproc);
+
+	/* release HW resources if needed */
+	rproc_unprepare_device(rproc);
+
+	rproc_disable_iommu(rproc);
+
+	rproc->table_ptr = NULL;
+out:
+	mutex_unlock(&rproc->lock);
+	return ret;
+}
+EXPORT_SYMBOL(rproc_detach);
+
 /**
  * rproc_get_by_phandle() - find a remote processor by phandle
  * @phandle: phandle to the rproc

@@ -662,6 +662,7 @@ rproc_of_resm_mem_entry_init(struct device *dev, u32 of_resm_idx, size_t len,
 
 int rproc_boot(struct rproc *rproc);
 void rproc_shutdown(struct rproc *rproc);
+int rproc_detach(struct rproc *rproc);
 int rproc_set_firmware(struct rproc *rproc, const char *fw_name);
 void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type);
 void rproc_coredump_using_sections(struct rproc *rproc);

@@ -2728,7 +2728,11 @@ static int rproc_panic_handler(struct notifier_block *nb, unsigned long event,
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(rproc, &rproc_list, node) {
-		if (!rproc->ops->panic || rproc->state != RPROC_RUNNING)
+		if (!rproc->ops->panic)
+			continue;
+
+		if (rproc->state != RPROC_RUNNING &&
+		    rproc->state != RPROC_ATTACHED)
 			continue;
 
 		d = rproc->ops->panic(rproc);

@@ -32,7 +32,8 @@ static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_
 		return -EFAULT;
 
 	if (!strncmp(cmd, "start", len)) {
-		if (rproc->state == RPROC_RUNNING)
+		if (rproc->state == RPROC_RUNNING ||
+		    rproc->state == RPROC_ATTACHED)
 			return -EBUSY;
 
 		ret = rproc_boot(rproc);

@@ -194,7 +194,8 @@ static ssize_t state_store(struct device *dev,
 	int ret = 0;
 
 	if (sysfs_streq(buf, "start")) {
-		if (rproc->state == RPROC_RUNNING)
+		if (rproc->state == RPROC_RUNNING ||
+		    rproc->state == RPROC_ATTACHED)
 			return -EBUSY;
 
 		ret = rproc_boot(rproc);

@@ -38,7 +38,8 @@ static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_
 
 		ret = rproc_boot(rproc);
 	} else if (!strncmp(cmd, "stop", len)) {
-		if (rproc->state != RPROC_RUNNING)
+		if (rproc->state != RPROC_RUNNING &&
+		    rproc->state != RPROC_ATTACHED)
 			return -EINVAL;
 
 		rproc_shutdown(rproc);

@@ -1796,6 +1796,10 @@ static int rproc_stop(struct rproc *rproc, bool crashed)
 	struct device *dev = &rproc->dev;
 	int ret;
 
+	/* No need to continue if a stop() operation has not been provided */
+	if (!rproc->ops->stop)
+		return -EINVAL;
+
 	/* Stop any subdevices for the remote processor */
 	rproc_stop_subdevices(rproc, crashed);
 

@@ -202,7 +202,8 @@ static ssize_t state_store(struct device *dev,
 		if (ret)
 			dev_err(&rproc->dev, "Boot failed: %d\n", ret);
 	} else if (sysfs_streq(buf, "stop")) {
-		if (rproc->state != RPROC_RUNNING)
+		if (rproc->state != RPROC_RUNNING &&
+		    rproc->state != RPROC_ATTACHED)
 			return -EINVAL;
 
 		rproc_shutdown(rproc);

@@ -1556,6 +1556,24 @@ static int rproc_set_rsc_table(struct rproc *rproc)
 		return ret;
 	}
 
+	/*
+	 * If it is possible to detach the remote processor, keep an untouched
+	 * copy of the resource table.  That way we can start fresh again when
+	 * the remote processor is re-attached, that is:
+	 *
+	 *      DETACHED -> ATTACHED -> DETACHED -> ATTACHED
+	 *
+	 * Free'd in rproc_reset_rsc_table_on_detach() and
+	 * rproc_reset_rsc_table_on_stop().
+	 */
+	if (rproc->ops->detach) {
+		rproc->clean_table = kmemdup(table_ptr, table_sz, GFP_KERNEL);
+		if (!rproc->clean_table)
+			return -ENOMEM;
+	} else {
+		rproc->clean_table = NULL;
+	}
+
 	rproc->cached_table = NULL;
 	rproc->table_ptr = table_ptr;
 	rproc->table_sz = table_sz;

@@ -1563,6 +1581,59 @@ static int rproc_set_rsc_table(struct rproc *rproc)
 	return 0;
 }
 
+static int rproc_reset_rsc_table_on_detach(struct rproc *rproc)
+{
+	struct resource_table *table_ptr;
+
+	/* A resource table was never retrieved, nothing to do here */
+	if (!rproc->table_ptr)
+		return 0;
+
+	/*
+	 * If we made it to this point a clean_table _must_ have been
+	 * allocated in rproc_set_rsc_table().  If one isn't present
+	 * something went really wrong and we must complain.
+	 */
+	if (WARN_ON(!rproc->clean_table))
+		return -EINVAL;
+
+	/* Remember where the external entity installed the resource table */
+	table_ptr = rproc->table_ptr;
+
+	/*
+	 * If we made it here the remote processor was started by another
+	 * entity and a cache table doesn't exist.  As such make a copy of
+	 * the resource table currently used by the remote processor and
+	 * use that for the rest of the shutdown process.  The memory
+	 * allocated here is free'd in rproc_detach().
+	 */
+	rproc->cached_table = kmemdup(rproc->table_ptr,
+				      rproc->table_sz, GFP_KERNEL);
+	if (!rproc->cached_table)
+		return -ENOMEM;
+
+	/*
+	 * Use a copy of the resource table for the remainder of the
+	 * shutdown process.
+	 */
+	rproc->table_ptr = rproc->cached_table;
+
+	/*
+	 * Reset the memory area where the firmware loaded the resource table
+	 * to its original value.  That way when we re-attach the remote
+	 * processor the resource table is clean and ready to be used again.
+	 */
+	memcpy(table_ptr, rproc->clean_table, rproc->table_sz);
+
+	/*
+	 * The clean resource table is no longer needed.  Allocated in
+	 * rproc_set_rsc_table().
+	 */
+	kfree(rproc->clean_table);
+
+	return 0;
+}
+
 /*
  * Attach to remote processor - similar to rproc_fw_boot() but without
  * the steps that deal with the firmware image.

@@ -1721,6 +1792,14 @@ static int __rproc_detach(struct rproc *rproc)
 	/* Stop any subdevices for the remote processor */
 	rproc_stop_subdevices(rproc, false);
 
+	/* the installed resource table is no longer accessible */
+	ret = rproc_reset_rsc_table_on_detach(rproc);
+	if (ret) {
+		dev_err(dev, "can't reset resource table: %d\n", ret);
+		return ret;
+	}
+
+
 	/* Tell the remote processor the core isn't available anymore */
 	ret = rproc->ops->detach(rproc);
 	if (ret) {

@@ -1997,6 +2076,9 @@ int rproc_detach(struct rproc *rproc)
 
 	rproc_disable_iommu(rproc);
 
+	/* Free the copy of the resource table */
+	kfree(rproc->cached_table);
+	rproc->cached_table = NULL;
 	rproc->table_ptr = NULL;
 out:
 	mutex_unlock(&rproc->lock);

@@ -514,6 +514,8 @@ struct rproc_dump_segment {
  * @recovery_disabled: flag that state if recovery was disabled
  * @max_notifyid: largest allocated notify id.
  * @table_ptr: pointer to the resource table in effect
+ * @clean_table: copy of the resource table without modifications.  Used
+ *		 when a remote processor is attached or detached from the core
  * @cached_table: copy of the resource table
  * @table_sz: size of @cached_table
  * @has_iommu: flag to indicate if remote processor is behind an MMU

@@ -550,6 +552,7 @@ struct rproc {
 	bool recovery_disabled;
 	int max_notifyid;
 	struct resource_table *table_ptr;
+	struct resource_table *clean_table;
 	struct resource_table *cached_table;
 	size_t table_sz;
 	bool has_iommu;

@@ -1634,6 +1634,47 @@ static int rproc_reset_rsc_table_on_detach(struct rproc *rproc)
 	return 0;
 }
 
+static int rproc_reset_rsc_table_on_stop(struct rproc *rproc)
+{
+	/* A resource table was never retrieved, nothing to do here */
+	if (!rproc->table_ptr)
+		return 0;
+
+	/*
+	 * If a cache table exists the remote processor was started by
+	 * the remoteproc core.  That cache table should be used for
+	 * the rest of the shutdown process.
+	 */
+	if (rproc->cached_table)
+		goto out;
+
+	/*
+	 * If we made it here the remote processor was started by another
+	 * entity and a cache table doesn't exist.  As such make a copy of
+	 * the resource table currently used by the remote processor and
+	 * use that for the rest of the shutdown process.  The memory
+	 * allocated here is free'd in rproc_shutdown().
+	 */
+	rproc->cached_table = kmemdup(rproc->table_ptr,
+				      rproc->table_sz, GFP_KERNEL);
+	if (!rproc->cached_table)
+		return -ENOMEM;
+
+	/*
+	 * Since the remote processor is being switched off the clean table
+	 * won't be needed.  Allocated in rproc_set_rsc_table().
+	 */
+	kfree(rproc->clean_table);
+
+out:
+	/*
+	 * Use a copy of the resource table for the remainder of the
+	 * shutdown process.
+	 */
+	rproc->table_ptr = rproc->cached_table;
+	return 0;
+}
+
 /*
  * Attach to remote processor - similar to rproc_fw_boot() but without
  * the steps that deal with the firmware image.