Re: [PATCH V2 1/2] memory: tegra: Wire up system sleep PM ops

[Ashish Mhetre <amhetre@nvidia.com>]

On 4/30/2026 2:09 PM, Jon Hunter wrote:
>
>
> On 30/04/2026 08:09, Ashish Mhetre wrote:
>> The tegra-mc platform driver does not register any dev_pm_ops, so the
>> the SoC-specific ->resume() is never invoked (e.g. tegra186_mc_resume)
>> on system wake. On Tegra186 and later this means MC client Stream-ID
>> override registers are not reprogrammed.
>>
>> Register a dev_pm_ops on the tegra-mc driver and route the system
>> resume callback into mc->soc->ops->resume() so the existing SID
>> restore path runs again on wake.
>>
>> No suspend callback is needed as the resume path reprograms all MC
>> state from the static SoC tables, so there is nothing to save.
>>
>> Fixes: fe3b082a6eb8 ("memory: tegra: Add SID override programming for 
>> MC clients")
>> Signed-off-by: Ashish Mhetre <amhetre@nvidia.com>
>> ---
>>   drivers/memory/tegra/mc.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/memory/tegra/mc.c b/drivers/memory/tegra/mc.c
>> index d620660da331..343ac0018eba 100644
>> --- a/drivers/memory/tegra/mc.c
>> +++ b/drivers/memory/tegra/mc.c
>> @@ -13,6 +13,7 @@
>>   #include <linux/of.h>
>>   #include <linux/of_platform.h>
>>   #include <linux/platform_device.h>
>> +#include <linux/pm.h>
>>   #include <linux/slab.h>
>>   #include <linux/sort.h>
>>   #include <linux/tegra-icc.h>
>> @@ -1010,10 +1011,23 @@ static void tegra_mc_sync_state(struct device 
>> *dev)
>>           icc_sync_state(dev);
>>   }
>>   +static int tegra_mc_resume(struct device *dev)
>> +{
>> +    struct tegra_mc *mc = dev_get_drvdata(dev);
>> +
>> +    if (mc->soc->ops && mc->soc->ops->resume)
>> +        return mc->soc->ops->resume(mc);
>
> I noticed that the tegra186_mc_resume never fails and always returns 
> 0. Given that this is the only resume handler, it seem that we should 
> change this to a void return type and then we can avoid the extra 
> return here. This also simplifies the next patch. So may be we should 
> add one more patch to change the return type for this resume callback.
>
> If we ever need to return a error code in the future we can add back, 
> but if we don't need it now, then I don't see why we should keep this.
>
> Jon
>

Okay, I'll update the return-type in new patch and send V3.

Thanks,
Ashish Mhetre