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

[Adrian Hunter <adrian.hunter@intel.com>]

On 3/01/24 11:20, Jorge Ramirez-Ortiz, Foundries wrote:
> On 03/01/24 10:03:38, Adrian Hunter wrote:
>> Thanks for doing that!  That seems to explain the mystery.
>>
>> You could hack the test to get an idea of how many successful
>> iterations there are before getting an error.
>>
>> For SDHCI, one difference between tuning and re-tuning is the
>> setting of bit-7 "Sampling Clock Select" of "Host Control 2 Register".
>> It is initially 0 and then set to 1 after the successful tuning.
>> Essentially, leaving it set to 1 is meant to speed up the re-tuning.
>> You could try setting it to zero instead, and see if that helps.
>> e.g.
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index c79f73459915..714d8cc39709 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -2732,6 +2732,7 @@ void sdhci_start_tuning(struct sdhci_host *host)
>>  	ctrl |= SDHCI_CTRL_EXEC_TUNING;
>>  	if (host->quirks2 & SDHCI_QUIRK2_TUNING_WORK_AROUND)
>>  		ctrl |= SDHCI_CTRL_TUNED_CLK;
>> +	ctrl &= ~SDHCI_CTRL_TUNED_CLK;
>>  	sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>>
>>  	/*
>>
> 
> 
> Yes with that change, the re-tuning reliability test does pass.
> 
> root@uz3cg-dwg-sec:/sys/kernel/debug/mmc0#  echo 52 > /sys/kernel/debug/mmc0/mmc0\:0001/test
> [  237.833585] mmc0: Starting tests of card mmc0:0001...
> [  237.838759] mmc0: Test case 52. Re-tuning reliability...
> [  267.845403] mmc0: Result: OK
> [  267.848365] mmc0: Tests completed.
> 
> 
> Unfortunately I still see the error when looping on RPMB reads.
> 
> For instance with this test script
>  $ while true; do rpmb_read m4hash; usleep 300; done
> 
> I can see the error triggering on the serial port after a minute or so.
> [  151.682907] sdhci-arasan ff160000.mmc: __mmc_blk_ioctl_cmd: data error -84
> 
> Causing OP-TEE to panic since the RPMB read returns an error
> E/TC:? 0
> E/TC:? 0 TA panicked with code 0xffff0000
> E/LD:  Status of TA 22250a54-0bf1-48fe-8002-7b20f1c9c9b1
> E/LD:   arch: aarch64
> [...]
> 
> if anything else springs to your mind I am happy to test of course - there are
> so many tunnables in this subsystem that experience is this area has exponential
> value (and I dont have much).
> 
> Would it make sense if re-tuning requests are rejected unless a minimum number
> of jiffies have passed? should I try that as a change?
> 
> or maybe delay a bit longer the RPMB access after a retune request?

It seems re-tuning is not working properly, so ideally the
SoC vendor / driver implementer would provide a solution.

There is also mmc_doing_retune() which could be used to skip
tuning execution entirely in the case of re-tuning.