linux-kernel - Re: [PATCH v3] mmc: Avoid reprogram all keys to Inline Crypto Engine for MMC runtime suspend resume

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Message-ID: <cead2d86-bac8-2d4f-1a7d-c9b90dc05a7c@oss.qualcomm.com>
Date: Fri, 9 Jan 2026 12:06:40 +0530
From: Neeraj Soni <neeraj.soni@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Debraj Mukhopadhyay <quic_dmukhopa@...cinc.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc: linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, kernel@...cinc.com,
        Neeraj Soni <quic_neersoni@...cinc.com>,
        Ram Prakash Gupta <quic_rampraka@...cinc.com>,
        Nitin Rawat <quic_nitirawa@...cinc.com>,
        Sachin Gupta <quic_sachgupt@...cinc.com>,
        Bhaskar Valaboju <quic_bhaskarv@...cinc.com>,
        Gaurav Kashyap <quic_gaurkash@...cinc.com>,
        Sarthak Garg <quic_sartgarg@...cinc.com>
Subject: Re: [PATCH v3] mmc: Avoid reprogram all keys to Inline Crypto Engine
 for MMC runtime suspend resume

Hi,

On 1/8/2026 3:13 PM, Konrad Dybcio wrote:
> On 1/6/26 7:49 AM, Neeraj Soni wrote:
>> Hi,
>>
>> Aplogies for replying so late to the queries.
>>
>> On 7/18/2025 5:35 PM, Konrad Dybcio wrote:
>>> On 7/18/25 1:02 PM, Debraj Mukhopadhyay wrote:
>>>> Crypto reprogram all keys is called for each MMC runtime
>>>> suspend/resume in current upstream design. If this is implemented
>>>> as a non-interruptible call to TEE for security, the cpu core is
>>>> blocked for execution while this call executes although the crypto
>>>> engine already has the keys. For example, glitches in audio/video
>>>> streaming applications have been observed due to this. Add the flag
>>>> MMC_CAP2_CRYPTO_NO_REPROG as part of host->caps2 to control reprogramming
>>>> keys to crypto engine for socs which dont require this feature.
>>>>
>>>> Signed-off-by: Seshu Madhavi Puppala <quic_spuppala@...cinc.com>
>>>> Co-developed-by: Ram Prakash Gupta <quic_rampraka@...cinc.com>
>>>> Signed-off-by: Ram Prakash Gupta <quic_rampraka@...cinc.com>
>>>> Co-developed-by: Sarthak Garg <quic_sartgarg@...cinc.com>
>>>> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>
>>>> Signed-off-by: Debraj Mukhopadhyay <quic_dmukhopa@...cinc.com>
>>>>
>>>> ---
> 
> [...]
> 
>>>> @@ -459,6 +459,11 @@ struct mmc_host {
>>>>  #define MMC_CAP2_CRYPTO		0
>>>>  #endif
>>>>  #define MMC_CAP2_ALT_GPT_TEGRA	(1 << 28)	/* Host with eMMC that has GPT entry at a non-standard location */
>>>> +#ifdef CONFIG_MMC_CRYPTO
>>>> +#define MMC_CAP2_CRYPTO_NO_REPROG	(1 << 29)	/* Host handles inline crypto key reprogramming */
>>>> +#else
>>>> +#define MMC_CAP2_CRYPTO_NO_REPROG	0
>>>> +#endif
>>> This (and the crypto ifdef for MMC_CAP2_CRYPTO) looks like unnecessary
>>> churn - crypto functions should never be called if the config is disabled
>>> in the first place
>> Do you suggest to remove #ifdef? I am not sure why #ifdef is used with MMC_CAP2_CRYPTO
>> (may be to reuse the bits if config is not defined) but for MMC_CAP2_CRYPTO_NO_REPROG we
>> followed the approach used for MMC_CAP2_CRYPTO.
> 
> We got plenty of bits, let's not waste the time of a programmer trying
> to figure out whether his particular combination of configs is going to
> collide with the reuse, I'd argue the ifdef is unnecessary
>
Sure. I will remove the #ifdef from MMC_CAP2_CRYPTO and MMC_CAP2_CRYPTO_NO_REPROG in next patch.
 
> Konrad
> 
Regards
Neeraj