Re: [PATCH] mmc: dw_mmc: Disable SDIO interrupts while suspended to fix suspend/resume

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On 2019/4/22 23:21, Doug Anderson wrote:
Hi,

On Wed, Apr 10, 2019 at 3:13 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:

Processing SDIO interrupts while dw_mmc is suspended (or partly
suspended) seems like a bad idea.  We really don't want to be
processing them until we've gotten ourselves fully powered up.

You might be wondering how it's even possible to become suspended when
an SDIO interrupt is active.  As can be seen in
dw_mci_enable_sdio_irq(), we explicitly keep dw_mmc out of runtime
suspend when the SDIO interrupt is enabled.  ...but even though we
stop normal runtime suspend transitions when SDIO interrupts are
enabled, the dw_mci_runtime_suspend() can still get called for a full
system suspend.

Let's handle all this by explicitly masking SDIO interrupts in the
suspend call and unmasking them later in the resume call.  To do this
cleanly I'll keep track of whether the client requested that SDIO
interrupts be enabled so that we can reliably restore them regardless
of whether we're masking them for one reason or another.

Without this fix it can be seen that rk3288-veyron Chromebooks with
Marvell WiFi would sometimes fail to resume WiFi even after picking my
recent mwifiex patch [1].  Specifically you'd see messages like this:
   mwifiex_sdio mmc1:0001:1: Firmware wakeup failed
   mwifiex_sdio mmc1:0001:1: PREP_CMD: FW in reset state

...and tracing through the resume code in the failing cases showed
that we were processing a SDIO interrupt really early in the resume
call.

NOTE: downstream in Chrome OS 3.14 and 3.18 kernels (both of which
support the Marvell SDIO WiFi card) we had a patch ("CHROMIUM: sdio:
Defer SDIO interrupt handling until after resume") [2].  Presumably
this is the same problem that was solved by that patch.

[1] https://lkml.kernel.org/r/20190404040106.40519-1-dianders@xxxxxxxxxxxx
[2] https://crrev.com/c/230765

Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---
I didn't put any "Fixes" tag here, but presumably this could be
backported to whichever kernels folks found it useful for.  I have at
least confirmed that kernels v4.14 and v4.19 (as well as v5.1-rc2)
show the problem.  It is very easy to pick this to v4.19 and it
definitely fixes the problem there.

I haven't spent the time to pick this to 4.14 myself, but presumably
it wouldn't be too hard to backport this as far as v4.13 since that
contains commit 32dba73772f8 ("mmc: dw_mmc: Convert to use
MMC_CAP2_SDIO_IRQ_NOTHREAD for SDIO IRQs").  Prior to that it might
make sense for anyone experiencing this problem to just pick the old
CHROMIUM patch to fix them.

  drivers/mmc/host/dw_mmc.c | 24 ++++++++++++++++++++----
  drivers/mmc/host/dw_mmc.h |  3 +++
  2 files changed, 23 insertions(+), 4 deletions(-)

Jaehoon / Shawn: any thoughts on this patch?

The intention seems reasonable to me, but just wonder if we need
mask/unmask SDIO interrupt when it's never used?  It's the same
situation for SDMMC_CLKEN_LOW_PWR that we couldn't stop providing
clock for SDIO cards, so I guess we need to check MMC_CAP_SDIO_IRQ
as well.


-Doug








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