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Subject[PATCH V2] sdhci: fix the timeout check window for clock and reset
From 87692fc090978bde8fe872f02d0023a57af6b492 Mon Sep 17 00:00:00 2001
From: Alek Du <alek.du@intel.com>
Date: Fri, 30 Nov 2018 14:02:28 +0800
Subject: [PATCH] sdhci: fix the timeout check window for clock and reset

We observed some fake timeouts on some devices, the log is like this:

case 1:
[159525.255629] mmc1: Internal clock never stabilised.
[159525.255818] mmc1: sdhci: ============ SDHCI REGISTER DUMP ===========
[159525.256049] mmc1: sdhci: Sys addr: 0x00000000 | Version: 0x00001002
[159525.256277] mmc1: sdhci: Blk size: 0x00000000 | Blk cnt: 0x00000000
[159525.256523] mmc1: sdhci: Argument: 0x00000000 | Trn mode: 0x00000000
[159525.256752] mmc1: sdhci: Present: 0x1fff0000 | Host ctl: 0x00000000
[159525.256979] mmc1: sdhci: Power: 0x0000000b | Blk gap: 0x00000080
[159525.257205] mmc1: sdhci: Wake-up: 0x00000000 | Clock: 0x0000fa03
From the clock control register dump, we are pretty sure the clock was
stablized.

case 2:
[ 914.550127] mmc1: Reset 0x2 never completed.
[ 914.550321] mmc1: sdhci: ============ SDHCI REGISTER DUMP ===========
[ 914.550608] mmc1: sdhci: Sys addr: 0x00000010 | Version: 0x00001002

After checking the sdhci code, we found the timeout check actually has a
little window that the CPU can be scheduled out and when it comes back,
the original time set or check is not valid.

Signed-off-by: Alek Du <alek.du@intel.com>
---
drivers/mmc/host/sdhci.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 99bdae53fa2e..af01f7d16eae 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -218,12 +218,17 @@ void sdhci_reset(struct sdhci_host *host, u8 mask)
/* hw clears the bit when it's done */
while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
if (ktime_after(ktime_get(), timeout)) {
+ /* check it again, since there is a window between
+ bit check and time check */
+ if (!(sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask))
+ break;
pr_err("%s: Reset 0x%x never completed.\n",
mmc_hostname(host->mmc), (int)mask);
sdhci_dumpregs(host);
return;
+ } else {
+ udelay(10);
}
- udelay(10);
}
}
EXPORT_SYMBOL_GPL(sdhci_reset);
@@ -1611,12 +1616,19 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)
while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
& SDHCI_CLOCK_INT_STABLE)) {
if (ktime_after(ktime_get(), timeout)) {
+ /* check it again since there is a window between
+ status check and time check */
+ if ((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
+ & SDHCI_CLOCK_INT_STABLE)
+ break;
pr_err("%s: Internal clock never stabilised.\n",
mmc_hostname(host->mmc));
sdhci_dumpregs(host);
return;
}
- udelay(10);
+ else {
+ udelay(10);
+ }
}

clk |= SDHCI_CLOCK_CARD_EN;
--
2.17.1
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