media: qcom: camss: Fix VFE-17x vfe_disable_output()

commit 3143ad2 upstream.

There are two problems with the current vfe_disable_output() routine.

Firstly we rightly use a spinlock to protect output->gen2.active_num
everywhere except for in the IDLE timeout path of vfe_disable_output().
Even if that is not racy "in practice" somehow it is by happenstance not
by design.

Secondly we do not get consistent behaviour from this routine. On
sc8280xp 50% of the time I get "VFE idle timeout - resetting". In this
case the subsequent capture will succeed. The other 50% of the time, we
don't hit the idle timeout, never do the VFE reset and subsequent
captures stall indefinitely.

Rewrite the vfe_disable_output() routine to

- Quiesce write masters with vfe_wm_stop()
- Set active_num = 0

remembering to hold the spinlock when we do so followed by

- Reset the VFE

Testing on sc8280xp and sdm845 shows this to be a valid fix.

Fixes: 7319cdf ("media: camss: Add support for VFE hardware version Titan 170")
Cc: stable@vger.kernel.org
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/media/platform/qcom/camss/camss-vfe-170.c

@@ -7,7 +7,6 @@
  * Copyright (C) 2020-2021 Linaro Ltd.
  */
 
-#include <linux/delay.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
@@ -494,35 +493,20 @@ static int vfe_enable_output(struct vfe_line *line)
 	return 0;
 }
 
-static int vfe_disable_output(struct vfe_line *line)
+static void vfe_disable_output(struct vfe_line *line)
 {
 	struct vfe_device *vfe = to_vfe(line);
 	struct vfe_output *output = &line->output;
 	unsigned long flags;
 	unsigned int i;
-	bool done;
-	int timeout = 0;
-
-	do {
-		spin_lock_irqsave(&vfe->output_lock, flags);
-		done = !output->gen2.active_num;
-		spin_unlock_irqrestore(&vfe->output_lock, flags);
-		usleep_range(10000, 20000);
-
-		if (timeout++ == 100) {
-			dev_err(vfe->camss->dev, "VFE idle timeout - resetting\n");
-			vfe_reset(vfe);
-			output->gen2.active_num = 0;
-			return 0;
-		}
-	} while (!done);
 
 	spin_lock_irqsave(&vfe->output_lock, flags);
 	for (i = 0; i < output->wm_num; i++)
 		vfe_wm_stop(vfe, output->wm_idx[i]);
+	output->gen2.active_num = 0;
 	spin_unlock_irqrestore(&vfe->output_lock, flags);
 
-	return 0;
+	vfe_reset(vfe);
 }
 
 /*