15.01.2021 18:35, Thierry Reding пишет:
> On Tue, Jan 12, 2021 at 03:58:31PM +0300, Dmitry Osipenko wrote:
>> Reset hardware in order to bring it into a predictable state.
>>
>> Tested-by: Peter Geis <pgwipeout@xxxxxxxxx>
>> Tested-by: Nicolas Chauvet <kwizart@xxxxxxxxx>
>> Signed-off-by: Dmitry Osipenko <digetx@xxxxxxxxx>
>> ---
>> sound/pci/hda/hda_tegra.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>>
>> diff --git a/sound/pci/hda/hda_tegra.c b/sound/pci/hda/hda_tegra.c
>> index 4c799661c2f6..e406b7980f31 100644
>> --- a/sound/pci/hda/hda_tegra.c
>> +++ b/sound/pci/hda/hda_tegra.c
>> @@ -17,6 +17,7 @@
>> #include <linux/moduleparam.h>
>> #include <linux/mutex.h>
>> #include <linux/of_device.h>
>> +#include <linux/reset.h>
>> #include <linux/slab.h>
>> #include <linux/time.h>
>> #include <linux/string.h>
>> @@ -70,6 +71,7 @@
>> struct hda_tegra {
>> struct azx chip;
>> struct device *dev;
>> + struct reset_control *reset;
>> struct clk_bulk_data clocks[3];
>> unsigned int nclocks;
>> void __iomem *regs;
>> @@ -167,6 +169,12 @@ static int __maybe_unused hda_tegra_runtime_resume(struct device *dev)
>> struct hda_tegra *hda = container_of(chip, struct hda_tegra, chip);
>> int rc;
>>
>> + if (!(chip && chip->running)) {
>
> Isn't that check for !chip a bit redundant? If that pointer isn't valid,
> we're just going to go crash when dereferencing hda later on, so I think
> this can simply be:
>
> if (!chip->running)
>
> I guess you took this from the inverse check below, but I think we can
> also drop it from there, perhaps in a separate patch.
>
>> + rc = reset_control_assert(hda->reset);
>> + if (rc)
>> + return rc;
>> + }
>> +
>> rc = clk_bulk_prepare_enable(hda->nclocks, hda->clocks);
>> if (rc != 0)
>> return rc;
>> @@ -176,6 +184,10 @@ static int __maybe_unused hda_tegra_runtime_resume(struct device *dev)
>> /* disable controller wake up event*/
>> azx_writew(chip, WAKEEN, azx_readw(chip, WAKEEN) &
>> ~STATESTS_INT_MASK);
>> + } else {
>> + rc = reset_control_reset(hda->reset);
>
> The "if (chip)" part definitely doesn't make sense after this anymore
> because now if chip == NULL, then we end up in here and dereference an
> invalid "hda" pointer.
Okay, I took a note for the v3.
> Also, why reset_control_reset() here? We'll reach this if we ran
> reset_control_assert() above, so this should just be
> reset_control_deassert() to undo that, right? I suppose it wouldn't hurt
> to put throw that standard usleep_range() in there as well that we use
> to wait between reset assert and deassert to make sure the clocks have
> stabilized and the reset has indeed propagated through the whole IP.
The reset_control_reset() does the delaying before the deassert, i.e. it
does assert -> udelay(1) -> deassert.
https://elixir.free-electrons.com/linux/v5.11-rc3/source/drivers/clk/tegra/clk.c#L133
The reset_control_reset() usage appears to be a bit more code-tidy
variant in comparison to delaying directly. But I don't mind to use
delay + reset_control_deassert() directly since it may not be obvious to
everyone what reset_control_reset() does.
I'll change it in v3.
