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Subject[RFC PATCH 1/2] mmc: sdhci: Manually check card status after reset
Date
There is a race condition between resetting the SDHCI controller and
disconnecting the card.

For example:
0) Card is connected and transferring data
1) mmc_sd_reset is called to reset the controller due to a data error
2) sdhci_set_ios calls sdhci_do_reset
3) SOFT_RESET_ALL is toggled which clears the IRQs the controller has
configured.
4) Wait for SOFT_RESET_ALL to clear
5) CD logic notices card is gone and CARD_PRESENT goes low, but since the
IRQs are not configured a CARD_REMOVED interrupt is never raised.
6) IRQs are enabled again
7) mmc layer never notices the device is disconnected. The SDHCI layer
will keep returning -ENOMEDIUM. This results in a card that is always
present and not functional.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
---
You can see an example of the following two patches here:
https://privatebin.net/?b0f5953716d34ca6#C699bCBQ99NdvspfDW7CMucT8CJG4DgL+yUNPyepDCo=
Line 8213: EILSEQ
Line 8235: SDHC is hard reset
Line 8240: Controller completes reset and card is no longer present
Line 8379: mmc_sd_reset notices card is missing and issues a card_event
and schedules a detect change.
Line 8402: Don't init the card since it's already gone.
Line 8717: Marks card as removed
Line 8820: mmc_sd_remove removes the block device

I am running into a kernel panic. A task gets stuck for more than 120
seconds. I keep seeing blkdev_close in the stack trace, so maybe I'm not
calling something correctly?

Here is the panic: https://privatebin.net/?8ec48c1547d19975#dq/h189w5jmTlbMKKAwZjUr4bhm7Q2AgvGdRqc5BxAc=

I sometimes see the following:
[ 547.943974] udevd[144]: seq 2350 '/devices/pci0000:00/0000:00:14.7/mmc_host/mmc0/mmc0:0001/block/mmcblk0/mmcblk0p1' is taking a long time

I was getting the kernel panic on a 4.14 kernel: https://chromium.googlesource.com/chromiumos/third_party/kernel/+/f3dc032faf4d074f20ada437e2d081a28ac699da/drivers/mmc/host
So I'm guessing I'm missing an upstream fix.

Do the patches look correct or am I doing something that would cause a
kernel panic?

I have a DUT setup with a GPIO I can use to toggle the CD pin. I ran a
test where I connect and then randomly, between 0s - 1s disconnect the
card. This got over 20k iterations before the panic. Though when I do it
manually and stop for 2 minutes the panic happens.

Any help would be appreciated.

Thanks,
Raul


drivers/mmc/core/sd.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)

diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
index 265e1aeeb9d8..9206c4297d66 100644
--- a/drivers/mmc/core/sd.c
+++ b/drivers/mmc/core/sd.c
@@ -1242,7 +1242,27 @@ static int mmc_sd_runtime_resume(struct mmc_host *host)

static int mmc_sd_hw_reset(struct mmc_host *host)
{
+ int present;
mmc_power_cycle(host, host->card->ocr);
+
+ present = host->ops->get_cd(host);
+
+ /* The card status could have changed while resetting. */
+ if ((mmc_card_removed(host->card) && present) ||
+ (!mmc_card_removed(host->card) && !present)) {
+ pr_info("%s: card status changed during reset\n",
+ mmc_hostname(host));
+ host->ops->card_event(host);
+ mmc_detect_change(host, 0);
+ }
+
+ /* Don't perform unnecessary transactions if the card is missing. */
+ if (!present) {
+ pr_info("%s: card was removed during reset\n",
+ mmc_hostname(host));
+ return -ENOMEDIUM;
+ }
+
return mmc_sd_init_card(host, host->card->ocr, host->card);
}

--
2.21.0.593.g511ec345e18-goog
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