Re: [PATCH RFC 0/2] Avoid reprogram all keys to Inline Crypto Engine for MMC runtime suspend resume

[Seshu Madhavi Puppala <quic_spuppala@quicinc.com>]

On 10/25/2024 2:12 PM, Ulf Hansson wrote:
> On Fri, 25 Oct 2024 at 04:56, Eric Biggers <ebiggers@kernel.org> wrote:
>>
>> On Fri, Oct 25, 2024 at 01:07:18AM +0200, Ulf Hansson wrote:
>>> On Wed, 23 Oct 2024 at 23:31, Eric Biggers <ebiggers@kernel.org> wrote:
>>>>
>>>> On Sun, Oct 06, 2024 at 07:25:28PM +0530, Seshu Madhavi Puppala wrote:
>>>>> Crypto reprogram all keys is called for each MMC runtime
>>>>> suspend/resume in current upstream design.
>>>>
>>>> Is that correct?  I thought that similar to what is done for UFS, the key
>>>> reprogramming happens only after the MMC controller is reset.  I thought that is
>>>> different from a runtime suspend.
>>>
>>> Looks like Seshu is not really worried about the host's runtime
>>> suspend, but the card's runtime suspend.
>>>
>>> Perhaps there are some out of tree code involved here that makes use
>>> of MMC_CAP_AGGRESSIVE_PM, which is what allows the card to be runtime
>>> suspended?
>>>
>>>>
>>>> If it's in fact triggering more often, maybe that is what needs to be fixed?
>>>
>>> We could extend the runtime PM autosusend timeout for the card, if
>>> that makes sense.
>>>
This change aims to address host side feature by not tying it up to card 
side flag/feature.
>>> Kind regards
>>> Uffe
>>
>> The keyslots are being reprogrammed from mmc_set_initial_state(), which is
>> documented as:
>>
>>      /*
>>       * Set initial state after a power cycle or a hw_reset.
>>       */
>>      void mmc_set_initial_state(struct mmc_host *host)
>>
>> It's called by: mmc_power_up(), mmc_power_off(), _mmc_hw_reset(), and
>> mmc_sdio_sw_reset().
>>
>> Can that mean a power cycle of the card, not a power cycle of the host
>> controller?
> 
> Yes, that's correct.
> 
> Well, indirectly the host is likely to be power cycled too, but not necessarily.
> 
>> The keyslots are part of the host controller, so that may explain
>> the problem.  The keyslots should be reprogrammed only when the host controller
>> is reset, as that is when they are lost.  (And it should not be skipped entirely
>> as this patchset does, as a host controller reset is possible.)
>>

This will be update via a separate patch by invoking reprogram_all_keys 
API from sdhci_msm_gcc_reset() API 
https://github.com/torvalds/linux/blob/master/drivers/mmc/host/sdhci-msm.c#L2363

Thanks,
Seshu

>> I am not an expert in MMC or in the details of how Qualcomm ICE is wired up to
>> the system, so I might have this wrong.  But let me know if it sounds right.
> 
> It sounds reasonable to me, but I also don't know the HW well enough
> to be able to tell.
> 
> Looks like we need some more input from Seshu and the QC folkz to
> understand better.
> 
> Kind regards
> Uffe