From: Patrice Chotard <patrice.chotard@foss.st.com>

With STM32 QSPI, it is possible to poll the status register of the device.
This could be done to offload the CPU during an operation (erase or
program a SPI NAND for example).

spi_mem_poll_status API has been added to handle this feature.
This new function take care of the offload/non-offload cases.

For the non-offload case, use read_poll_timeout() to poll the status in
order to release CPU during this phase.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Signed-off-by: Christophe Kerello <redacted>
---
Changes in v2:
  - Indicates the spi_mem_poll_status() timeout unit
  - Use 2-byte wide status register
  - Add spi_mem_supports_op() call in spi_mem_poll_status()
  - Add completion management in spi_mem_poll_status()
  - Add offload/non-offload case mangement in spi_mem_poll_status()
  - Optimize the non-offload case by using read_poll_timeout()

 drivers/spi/spi-mem.c       | 71 +++++++++++++++++++++++++++++++++++++
 include/linux/spi/spi-mem.h | 10 ++++++
 2 files changed, 81 insertions(+)

diff --git a/drivers/spi/spi-mem.c b/drivers/spi/spi-mem.c
index 1513553e4080..3f29c604df7d 100644
--- a/drivers/spi/spi-mem.c
+++ b/drivers/spi/spi-mem.c

@@ -6,6 +6,7 @@
  * Author: Boris Brezillon <boris.brezillon@bootlin.com>
  */
 #include <linux/dmaengine.h>
+#include <linux/iopoll.h>
 #include <linux/pm_runtime.h>
 #include <linux/spi/spi.h>
 #include <linux/spi/spi-mem.h>

@@ -743,6 +744,75 @@ static inline struct spi_mem_driver *to_spi_mem_drv(struct device_driver *drv)
 	return container_of(drv, struct spi_mem_driver, spidrv.driver);
 }
 
+/**
+ * spi_mem_finalize_op - report completion of spi_mem_op
+ * @ctlr: the controller reporting completion
+ *
+ * Called by SPI drivers using the spi-mem spi_mem_poll_status()
+ * implementation to notify it that the current spi_mem_op has
+ * finished.
+ */
+void spi_mem_finalize_op(struct spi_controller *ctlr)
+{
+	complete(&ctlr->xfer_completion);
+}
+EXPORT_SYMBOL_GPL(spi_mem_finalize_op);
+
+/**
+ * spi_mem_poll_status() - Poll memory device status
+ * @mem: SPI memory device
+ * @op: the memory operation to execute
+ * @mask: status bitmask to ckeck
+ * @match: (status & mask) expected value
+ * @timeout_ms: timeout in milliseconds
+ *
+ * This function send a polling status request to the controller driver
+ *
+ * Return: 0 in case of success, -ETIMEDOUT in case of error,
+ *         -EOPNOTSUPP if not supported.
+ */
+int spi_mem_poll_status(struct spi_mem *mem,
+			const struct spi_mem_op *op,
+			u16 mask, u16 match, u16 timeout_ms)
+{
+	struct spi_controller *ctlr = mem->spi->controller;
+	unsigned long ms;
+	int ret = -EOPNOTSUPP;
+	int exec_op_ret;
+	u16 *status;
+
+	if (!spi_mem_supports_op(mem, op))
+		return ret;

+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_mem_poll_status);
+
 static int spi_mem_probe(struct spi_device *spi)
 {
 	struct spi_mem_driver *memdrv = to_spi_mem_drv(spi->dev.driver);

@@ -763,6 +833,7 @@ static int spi_mem_probe(struct spi_device *spi)
 	if (IS_ERR_OR_NULL(mem->name))
 		return PTR_ERR_OR_ZERO(mem->name);
 
+	init_completion(&ctlr->xfer_completion);
 	spi_set_drvdata(spi, mem);
 
 	return memdrv->probe(mem);

diff --git a/include/linux/spi/spi-mem.h b/include/linux/spi/spi-mem.h
index 2b65c9edc34e..0fbf5d0a3d31 100644
--- a/include/linux/spi/spi-mem.h
+++ b/include/linux/spi/spi-mem.h

@@ -250,6 +250,7 @@ static inline void *spi_mem_get_drvdata(struct spi_mem *mem)
  *		  the currently mapped area), and the caller of
  *		  spi_mem_dirmap_write() is responsible for calling it again in
  *		  this case.
+ * @poll_status: poll memory device status
  *
  * This interface should be implemented by SPI controllers providing an
  * high-level interface to execute SPI memory operation, which is usually the

@@ -274,6 +275,9 @@ struct spi_controller_mem_ops {
 			       u64 offs, size_t len, void *buf);
 	ssize_t (*dirmap_write)(struct spi_mem_dirmap_desc *desc,
 				u64 offs, size_t len, const void *buf);
+	int (*poll_status)(struct spi_mem *mem,
+			   const struct spi_mem_op *op,
+			   u16 mask, u16 match, unsigned long timeout);
 };
 
 /**

@@ -369,6 +373,12 @@ devm_spi_mem_dirmap_create(struct device *dev, struct spi_mem *mem,
 void devm_spi_mem_dirmap_destroy(struct device *dev,
 				 struct spi_mem_dirmap_desc *desc);
 
+void spi_mem_finalize_op(struct spi_controller *ctlr);
+
+int spi_mem_poll_status(struct spi_mem *mem,
+			const struct spi_mem_op *op,
+			u16 mask, u16 match, u16 timeout);
+
 int spi_mem_driver_register_with_owner(struct spi_mem_driver *drv,
 				       struct module *owner);