linux-kernel - Re: [PATCH] mmc: rpmb: do not force a retune before RPMB switch

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Message-ID: <acd40f9b-a43a-4b74-bb78-3576a15d4d9b@intel.com>
Date:   Tue, 5 Dec 2023 22:14:32 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Jorge Ramirez-Ortiz <jorge@...ndries.io>, Avri.Altman@....com,
        ulf.hansson@...aro.org, christian.loehle@....com
Cc:     jinpu.wang@...os.com, axboe@...nel.dk, beanhuo@...ron.com,
        yibin.ding@...soc.com, victor.shih@...esyslogic.com.tw,
        asuk4.q@...il.com, hkallweit1@...il.com, yangyingliang@...wei.com,
        yebin10@...wei.com, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mmc: rpmb: do not force a retune before RPMB switch

On 5/12/23 22:12, Adrian Hunter wrote:
> On 4/12/23 17:01, Jorge Ramirez-Ortiz wrote:
>> Requesting a retune before switching to the RPMB partition has been
>> observed to cause CRC errors on the RPMB reads (-EILSEQ).
> 
> There are still 2 concerns:
> 1) We don't really know the root cause.  Have you determined
> if here are CRC errors in the main partition also?
> 2) Forcing this on everyone
> 
> The original idea was that because re-tuning cannot be
> done in RPMB, the need to re-rune in RPMB could be avoided
> by always re-tuning before switching to RPMB and then switching
> straight back. IIRC re-tuning should guarantee at least 4MB
> more I/O without issue.
> 
> The alternative to dropping re-tuning in this case could
> be to add a retry loop for MMC_DRV_OP_IOCTL_RPMB if the error
> is -EILSEQ

Actually, you could still do this patch as well because
a CRC error would cause re-tuning before the next retry.

> 
> 
>>
>> Since RPMB reads can not be retried, the clients would be directly
>> affected by the errors.
>>
>> This commit disables the request prior to RPMB switching while allowing
>> the pause interface to still request a retune before the pause for other
>> use cases.
>>
>> This was verified with the sdhci-of-arasan driver (ZynqMP) configured
>> for HS200 using two separate eMMC cards (DG4064 and 064GB2). In both
>> cases, the error was easy to reproduce triggering every few tenths of
>> reads.
>>
>> Signed-off-by: Jorge Ramirez-Ortiz <jorge@...ndries.io>
>> ---
>>  drivers/mmc/core/block.c | 2 +-
>>  drivers/mmc/core/host.c  | 7 ++++---
>>  drivers/mmc/core/host.h  | 2 +-
>>  3 files changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index f9a5cffa64b1..1d69078ad9b2 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -859,7 +859,7 @@ static int mmc_blk_part_switch_pre(struct mmc_card *card,
>>  			if (ret)
>>  				return ret;
>>  		}
>> -		mmc_retune_pause(card->host);
>> +		mmc_retune_pause(card->host, false);
>>  	}
>>  
>>  	return ret;
>> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
>> index 096093f7be00..a9b95aaa2235 100644
>> --- a/drivers/mmc/core/host.c
>> +++ b/drivers/mmc/core/host.c
>> @@ -119,13 +119,14 @@ void mmc_retune_enable(struct mmc_host *host)
>>  
>>  /*
>>   * Pause re-tuning for a small set of operations.  The pause begins after the
>> - * next command and after first doing re-tuning.
>> + * next command and, if retune is set, after first doing re-tuning.
>>   */
>> -void mmc_retune_pause(struct mmc_host *host)
>> +void mmc_retune_pause(struct mmc_host *host, bool retune)
>>  {
>>  	if (!host->retune_paused) {
>>  		host->retune_paused = 1;
>> -		mmc_retune_needed(host);
>> +		if (retune)
>> +			mmc_retune_needed(host);
> 
> Better to just drop mmc_retune_needed(host);
> 
>>  		mmc_retune_hold(host);
> 
> There is still a small chance that re-tuning
> is needed anyway in which case it will still be done.
> 
>>  	}
>>  }
>> diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h
>> index 48c4952512a5..321776b52270 100644
>> --- a/drivers/mmc/core/host.h
>> +++ b/drivers/mmc/core/host.h
>> @@ -18,7 +18,7 @@ void mmc_retune_disable(struct mmc_host *host);
>>  void mmc_retune_hold(struct mmc_host *host);
>>  void mmc_retune_release(struct mmc_host *host);
>>  int mmc_retune(struct mmc_host *host);
>> -void mmc_retune_pause(struct mmc_host *host);
>> +void mmc_retune_pause(struct mmc_host *host, bool retune);
>>  void mmc_retune_unpause(struct mmc_host *host);
>>  
>>  static inline void mmc_retune_clear(struct mmc_host *host)
>