Re: [alsa-devel] [PATCH 4/9] ASoC: tegra: add Tegra210 based I2S driver

[Sameer Pujar]

On 1/22/2020 11:53 AM, Dmitry Osipenko wrote:
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>
> 22.01.2020 07:32, Sameer Pujar ÐÐÑÐÑ:
> [snip]
> > > > > > +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.
> > > > > > +     int rx_fifo_th;
> > > > > Could rx_fifo_th be negative?
> > > > rx_fifo_th itself does not take negative values, explicit
> > > > typecasting> is avoided in "if" condition by declaring this as "int"
> > > Explicit typecasting isn't needed for integers.
> > What I meant was, rx_fifo_th is checked against a 'int' variable in an
> > "if" condition.
> What's the problem with comparing of unsigned with signed?

consider this example,
----
unsigned int x = 5;
int y = -1;

(x > y) is false.
----
Hence should be careful while using signed and unsigned comparisons.
> Besides, cif_conf.audio_ch > I2S_RX_FIFO_DEPTH can't be ever true, isn't
> it? I2S_RX_FIFO_DEPTH=64, channels_max=16

Yes true.
> Lastly, nothing stops you to make max_th unsigned.

will update.