On 1/22/2020 9:57 PM, Dmitry Osipenko wrote:
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22.01.2020 14:52, Jon Hunter пишет:
On 22/01/2020 07:16, Sameer Pujar wrote:
...
+static int tegra210_i2s_remove(struct platform_device *pdev)
+{
+ pm_runtime_disable(&pdev->dev);
+ if (!pm_runtime_status_suspended(&pdev->dev))
+ tegra210_i2s_runtime_suspend(&pdev->dev);
This breaks device's RPM refcounting if it was disabled in the active
state. This code should be removed. At most you could warn about the
unxpected RPM state here, but it shouldn't be necessary.
I guess this was added for safety and explicit suspend keeps clock
disabled.
Not sure if ref-counting of the device matters when runtime PM is
disabled and device is removed.
I see few drivers using this way.
It should matter (if I'm not missing something) because RPM should
be in
a wrecked state once you'll try to re-load the driver's module. Likely
that those few other drivers are wrong.
[snip]
Once the driver is re-loaded and RPM is enabled, I don't think it
would use
the same 'dev' and the corresponding ref count. Doesn't it use the new
counters?
If RPM is not working for some reason, most likely it would be the case
for other
devices. What best driver can do is probably do a force suspend during
removal if
already not done. I would prefer to keep, since multiple drivers still
have it,
unless there is a real harm in doing so.
I took a closer look and looks like the counter actually should be
reset. Still I don't think that it's a good practice to make changes
underneath of RPM, it may strike back.
If RPM is broken, it probably would have been caught during device usage.
I will remove explicit suspend here if no any concerns from other folks.
Thanks.
I recall that this was the preferred way of doing this from the RPM
folks. Tegra30 I2S driver does the same and Stephen had pointed me to
this as a reference.
I believe that this is meant to ensure that the
device is always powered-off regardless of it RPM is enabled or not and
what the current state is.
Yes, it was kinda actual for the case of unavailable RPM.
Anyways, /I think/ variant like this should have been more preferred:
if (!pm_runtime_enabled(&pdev->dev))
tegra210_i2s_runtime_suspend(&pdev->dev);
else
pm_runtime_disable(&pdev->dev);
I think it looks to be similar to what is there already.
pm_runtime_disable(&pdev->dev); // it would turn out to be a dummy call
if !RPM
if (!pm_runtime_status_suspended(&pdev->dev)) // it is true always if !RPM
tegra210_i2s_runtime_suspend(&pdev->dev);
Now for Tegra210 (or actually 64-bit Tegra) RPM is always enabled and so
we don't need to worry about the !RPM case. However, I still don't see
the harm in this.
There is no real harm today, but:
1. I'd prefer to be very careful with RPM in general, based on
previous experience.
2. It should be a bug if device isn't RPM-suspended during
of driver's removal. Thus the real problem needs to be fixed
rather than worked around.
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