[v3,00/10] Fix busydetect on Ux500 PL180/MMCI

Message

Linus Walleij June 11, 2023, 7:41 p.m. UTC

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 <[e-mail]>
---
Changes in v3:
- Unconditionally assign busy_status = 0
- Rewrite state machine states to just three
- Drop a patch that gets absorbed into another patch
- Drop patch to get busy state from the state machine, it was
  fishy, based on a misunderstanding and not needed
- Link to v2: https://lore.kernel.org/r/[e-mail]

Changes in v2:
- Drop pointless patch nr 1
- Unconditionally intialize some state variables
- Use a less fragile method to look for busy status when
  using busy detect, should fix Yann's problem
- Link to v1: https://lore.kernel.org/r/[e-mail]

---
Linus Walleij (10):
      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: Add busydetect timeout

 drivers/mmc/host/mmci.c             | 139 ++++++++++++++++++++++++++++--------
 drivers/mmc/host/mmci.h             |  15 ++++
 drivers/mmc/host/mmci_stm32_sdmmc.c |   6 +-
 3 files changed, 130 insertions(+), 30 deletions(-)
---
base-commit: ac9a78681b921877518763ba0e89202254349d1b
change-id: 20230405-pl180-busydetect-fix-66a0360d398a

Best regards,