[Linux-stm32] [PATCH 00/13] Fix busydetect on Ux500 PL180/MMCI

[Yann Gautier]

On 4/5/23 08:50, Linus Walleij wrote:
> This series fixes a pretty serious problem in the MMCI
> busy detect handling, discovered only after going up and
> down a ladder of refactorings.
> 
> The code is written expecting the Ux500 busy detect
> to fire two interrupts: one at the start of the busy
> signalling and one at the end of the busy signalling.
> 
> The root cause of the problem seen on some devices
> is that only the first IRQ arrives, and then the device
> hangs, waiting perpetually for the next IRQ to arrive.
> 
> This is eventually solved by adding a timeout using
> a delayed work that fire after 10 ms if the busy detect
> has not stopped at this point. (Other delay spans can
> be suggested.) This is the last patch in the series.
> 
> I included the rewrite of the entire busy detect logic
> to use a state machine as this makes it way easier to
> debug and will print messages about other error
> conditions as well.
> 
> The problem affects especially the Skomer
> (Samsung GT-I9070) and Kyle (Samsung SGH-I407).
> 
> It is fine to just apply this for the -next kernel,
> despite it fixes the busy detect that has been broken
> for these devices for a while, we can think about
> backporting a simpler version of the timeout for
> stable kernels if we want.
> 
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> ---
> Linus Walleij (13):
>        mmc: mmci: Only call busy_complete if callback defined
>        mmc: mmci: Clear busy_status when starting command
>        mmc: mmci: Unwind big if() clause
>        mmc: mmci: Stash status while waiting for busy
>        mmc: mmci: Break out error check in busy detect
>        mmc: mmci: Make busy complete state machine explicit
>        mmc: mmci: Retry the busy start condition
>        mmc: mmci: Use state machine state as exit condition
>        mmc: mmci: Use a switch statement machine
>        mmc: mmci: Break out a helper function
>        mmc: mmci: mmci_card_busy() from state machine
>        mmc: mmci: Drop end IRQ from Ux500 busydetect
>        mmc: mmci: Add busydetect timeout
> 
>   drivers/mmc/host/mmci.c             | 165 +++++++++++++++++++++++++++---------
>   drivers/mmc/host/mmci.h             |  17 ++++
>   drivers/mmc/host/mmci_stm32_sdmmc.c |   6 +-
>   3 files changed, 149 insertions(+), 39 deletions(-)
> ---
> base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6
> change-id: 20230405-pl180-busydetect-fix-66a0360d398a
> 
> Best regards,

Hi Linus,

With this series, it is no more possible to switch to UHS modes on 
STM32MP1. I will add some traces and try to see what's wrong or missing 
to have it working again.
I've tested on STM32MP157F-EV1 board and got those traces:
[    3.186504] mmc0: Skipping voltage switch
[    3.302170] mmc0: new high speed SDHC card at address aaaa

Whereas with the previous version I had:
[    1.882084] mmc0: new ultra high speed DDR50 SDHC card at address aaaa
[    1.899142] mmcblk0: mmc0:aaaa SC16G 14.8 GiB

On STM32MP13 that can do SDR104 (tested on an internal board), it fails 
to initialized the card:
[    3.194072] mmc0: error -110 whilst initialising SD card

When adding some dynamic debug traces, I can see this in the trace:
[   78.039648] mmc0: Signal voltage switch failed, power cycling card

I'll try to add more traces to see what happens exactly.


Best regards,
Yann