Re: [PATCH 5/9] soc: apple: Add RTKit IPC library

On Mon, Mar 21, 2022 at 5:50 PM Sven Peter [off-list ref] wrote:

Apple SoCs such as the M1 come with multiple embedded co-processors
running proprietary firmware. Communication with those is established
over a simple mailbox using the RTKit IPC protocol.

Signed-off-by: Sven Peter <redacted>

+
+#define rtk_err(format, arg...) dev_err(rtk->dev, "RTKit: " format, ##arg)
+#define rtk_warn(format, arg...) dev_warn(rtk->dev, "RTKit: " format, ##arg)
+#define rtk_info(format, arg...) dev_info(rtk->dev, "RTKit: " format, ##arg)
+#define rtk_dbg(format, arg...) dev_dbg(rtk->dev, "RTKit: " format, ##arg)

I generally don't like the custom printing macros, please just open-code
the prints where they are used, that makes it easier for other kernel
developers to see exactly what is being printed.

+enum { APPLE_RTKIT_WORK_MSG,
+       APPLE_RTKIT_WORK_REINIT,
+};
+
+enum { APPLE_RTKIT_PWR_STATE_OFF = 0x00,
+       APPLE_RTKIT_PWR_STATE_SLEEP = 0x01,
+       APPLE_RTKIT_PWR_STATE_GATED = 0x02,
+       APPLE_RTKIT_PWR_STATE_QUIESCED = 0x10,
+       APPLE_RTKIT_PWR_STATE_ON = 0x20,
+};

This is an odd indentation style, I would insert a newline after the 'enum {'

+static int apple_rtkit_worker(void *data)
+{
+       struct apple_rtkit *rtk = data;
+       struct apple_rtkit_work work;
+
+       while (!kthread_should_stop()) {
+               wait_event_interruptible(rtk->wq,
+                                        kfifo_len(&rtk->work_fifo) > 0 ||
+                                                kthread_should_stop());
+
+               if (kthread_should_stop())
+                       break;
+
+               while (kfifo_out_spinlocked(&rtk->work_fifo, &work, 1,
+                                           &rtk->work_lock) == 1) {
+                       switch (work.type) {
+                       case APPLE_RTKIT_WORK_MSG:
+                               apple_rtkit_rx(rtk, &work.msg);
+                               break;
+                       case APPLE_RTKIT_WORK_REINIT:
+                               apple_rtkit_do_reinit(rtk);
+                               break;
+                       }
+               }

It looks like you add quite a bit of complexity by using a custom
worker thread implementation. Can you explain what this is
needed for? Isn't this roughly the same thing that one would
get more easily with create_singlethread_workqueue()?

+#if IS_ENABLED(CONFIG_APPLE_RTKIT)

Instead of allowing the interface to be used without CONFIG_APPLE_RTKIT,
I think it is sufficient to allow the driver itself to be built with
CONFIG_COMPILE_TEST (as you already do), and then have
drivers using it marked as 'depends on APPLE_RTKIT'
unconditionally.

+/*
+ * Initializes the internal state required to handle RTKit. This
+ * should usually be called within _probe.
+ *
+ * @dev: Pointer to the device node this coprocessor is assocated with
+ * @cookie: opaque cookie passed to all functions defined in rtkit_ops
+ * @mbox_name: mailbox name used to communicate with the co-processor
+ * @mbox_idx: mailbox index to be used if mbox_name is NULL
+ * @ops: pointer to rtkit_ops to be used for this co-processor
+ */
+struct apple_rtkit *apple_rtkit_init(struct device *dev, void *cookie,
+                                    const char *mbox_name, int mbox_idx,
+                                    const struct apple_rtkit_ops *ops);
+
+/*
+ * Dev-res managed version of apple_rtkit_init.
+ */
+struct apple_rtkit *devm_apple_rtkit_init(struct device *dev, void *cookie,
+                                         const char *mbox_name, int mbox_idx,
+                                         const struct apple_rtkit_ops *ops);

Do we need to export both of these?

         Arnd

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