Re: [PATCH v8 2/3] CMDQ: Mediatek CMDQ driver

Hi CK,

Reply inline.

On Mon, 2016-05-30 at 14:49 +0800, CK Hu wrote:

Hi, HS:

Some comments inline.

On Mon, 2016-05-30 at 11:19 +0800, HS Liao wrote:

...

quoted

+static void cmdq_thread_irq_handler(struct cmdq *cmdq, int tid)
+{
+	struct cmdq_thread *thread = &cmdq->thread[tid];
+	unsigned long flags = 0L;
+	u32 irq_flag;
+
+	spin_lock_irqsave(&cmdq->exec_lock, flags);
+
+	irq_flag = cmdq_thread_readl(thread, CMDQ_THR_IRQ_STATUS);
+	cmdq_thread_writel(thread, ~irq_flag, CMDQ_THR_IRQ_STATUS);
+
+	/*
+	 * Another CPU core could run "release task" right before we acquire
+	 * the spin lock, and thus reset / disable this GCE thread, so we
+	 * need to check the enable bit of this GCE thread.
+	 */
+	if (!(cmdq_thread_readl(thread, CMDQ_THR_ENABLE_TASK) &
+	      CMDQ_THR_ENABLED))
+		irq_flag = 0;

These three statement (clear irq flag and detect thread enable) can be
moved into cmdq_handle_error_done() and the duplicated part in
cmdq_task_handle_error_result() can be removed. Even though
cmdq_task_handle_error_result() need not check thread enable, it would
not influence the flow.

Will do.

quoted

+
+	cmdq_handle_error_done(cmdq, thread, irq_flag);
+	spin_unlock_irqrestore(&cmdq->exec_lock, flags);
+}

...

quoted

+static int cmdq_task_handle_error_result(struct cmdq_task *task)
+{
+	struct cmdq *cmdq = task->cmdq;
+	struct device *dev = cmdq->dev;
+	struct cmdq_thread *thread = task->thread;
+	struct cmdq_task *next_task, *prev_task;
+	u32 irq_flag;
+
+	/* suspend GCE thread to ensure consistency */
+	WARN_ON(cmdq_thread_suspend(cmdq, thread) < 0);
+
+	/* ISR has handled this error task */
+	if (task->task_state == TASK_STATE_ERROR) {
+		next_task = list_first_entry_or_null(&thread->task_busy_list,
+				struct cmdq_task, list_entry);
+		if (next_task) /* move to next task */
+			cmdq_thread_writel(thread, next_task->pa_base,
+					   CMDQ_THR_CURR_ADDR);
+		cmdq_thread_resume(thread);
+		return -ECANCELED;
+	}
+
+	/*
+	 * Save next_task and prev_task in advance
+	 * since cmdq_handle_error_done will remove list_entry.
+	 */
+	next_task = prev_task = NULL;
+	if (task->list_entry.next != &thread->task_busy_list)
+		next_task = list_next_entry(task, list_entry);
+	if (task->list_entry.prev != &thread->task_busy_list)
+		prev_task = list_prev_entry(task, list_entry);

I think there is always no previous task because task order in
thread->task_busy_list is the same as in cmdq->task_release_wq. So each
task processed by release work should be the first item in
thread->task_busy_list or be removed from thread->task_busy_list.

Will remove previous task.

quoted

+
+	/*
+	 * Although IRQ is disabled, GCE continues to execute.
+	 * It may have pending IRQ before GCE thread is suspended,
+	 * so check this condition again.
+	 */
+	irq_flag = cmdq_thread_readl(thread, CMDQ_THR_IRQ_STATUS);
+	cmdq_handle_error_done(cmdq, thread, irq_flag);
+	cmdq_thread_writel(thread, ~irq_flag, CMDQ_THR_IRQ_STATUS);
+
+	if (task->task_state == TASK_STATE_DONE) {
+		cmdq_thread_resume(thread);
+		return 0;
+	}
+
+	if (task->task_state == TASK_STATE_ERROR) {
+		dev_err(dev, "task 0x%p error\n", task);
+		if (next_task) /* move to next task */
+			cmdq_thread_writel(thread, next_task->pa_base,
+					   CMDQ_THR_CURR_ADDR);
+		cmdq_thread_resume(thread);
+		return -ECANCELED;
+	}
+
+	/* Task is running, so we force to remove it. */
+	dev_err(dev, "task 0x%p timeout or killed\n", task);

No 'kill' state.

From CMDQ v8, there is no killed task.

I will rewrite output message.

quoted

+	task->task_state = TASK_STATE_ERROR;
+
+	if (prev_task) {
+		u64 *prev_va = prev_task->va_base;
+		u64 *curr_va = task->va_base;
+
+		/* copy JUMP instruction */
+		prev_va[prev_task->num_cmd - 1] = curr_va[task->num_cmd - 1];
+
+		cmdq_thread_invalidate_fetched_data(thread);
+	} else if (next_task) { /* move to next task */
+		cmdq_thread_writel(thread, next_task->pa_base,
+				   CMDQ_THR_CURR_ADDR);
+	}

Just one statement in 'else if' part. So remove the parentheses.

I think we should keep this parentheses.

Quote from CodingStyle document:

This does not apply if only one branch of a conditional statement is a
single
statement; in the latter case use braces in both branches:

if (condition) {
        do_this();
        do_that();
} else {
        otherwise();
}

quoted

+
+	list_del(&task->list_entry);
+	cmdq_thread_resume(thread);
+
+	/* call cb here to prevent lock */

I think these three statements should be place together and there should
be no this comment.

1. Change task state to DONE or ERROR.
2. Callback
3. Remove task from task_busy_list.

I will put these three statements together and wrap up them as a
function.

quoted

+	if (task->cb.cb) {
+		struct cmdq_cb_data cmdq_cb_data;
+
+		cmdq_cb_data.err = true;
+		cmdq_cb_data.data = task->cb.data;
+		task->cb.cb(cmdq_cb_data);
+	}
+
+	return -ECANCELED;
+}

...

quoted

+static int cmdq_suspend(struct device *dev)
+{
+	struct cmdq *cmdq = dev_get_drvdata(dev);
+	u32 exec_threads;
+
+	mutex_lock(&cmdq->task_mutex);
+	cmdq->suspended = true;
+	mutex_unlock(&cmdq->task_mutex);
+
+	exec_threads = readl(cmdq->base + CMDQ_CURR_LOADED_THR);
+	if ((exec_threads & CMDQ_THR_EXECUTING) && !cmdq_task_is_empty(cmdq)) {
+		dev_err(dev, "wait active tasks timeout.\n");
+		flush_workqueue(cmdq->task_release_wq);
+	}

Maybe it need not to check exec_threads, it may be written as:

	if (!cmdq_task_is_empty(cmdq))
		dev_err(dev, "wait active tasks timeout.\n");

	flush_workqueue(cmdq->task_release_wq);

Even though task_busy_list is empty, that does not mean every task in
cmdq->task_release_wq is finished. So always do flush
cmdq->task_release_wq.

Will do.

quoted

+	return 0;
+}
+

...

Regards,
CK

Thanks,
HS

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