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

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On 1/5/24 09:49, Jorge Ramirez-Ortiz, Foundries wrote:
On 04/01/24 20:34:09, Adrian Hunter wrote:
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.

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)
  	if (host->quirks2 & SDHCI_QUIRK2_TUNING_WORK_AROUND)
  	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.

Makes sense to me too. I am copying Michal on the DL.

We will take look at it.


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