[PATCH V3] sdhci: fix the timeout check window for clock and reset

Du, Alek
2018-12-05T03:14:50Z

>From bcb38577961823b4f8f2cc0aec7dd450a81b6ddc 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 premature timeouts on a virtualization platform, 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
...
[159525.257205] 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.

Fixes: 5a436cc0af62 ("mmc: sdhci: Optimize delay loops")
Signed-off-by: Alek Du <alek.du@intel.com>
Cc: stable@vger.kernel.org # v4.12+
---
drivers/mmc/host/sdhci.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 99bdae53fa2e..451b08a818a9 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -216,8 +216,12 @@ void sdhci_reset(struct sdhci_host *host, u8 mask)
timeout = ktime_add_ms(ktime_get(), 100);

/* hw clears the bit when it's done */
- while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
- if (ktime_after(ktime_get(), timeout)) {
+ while (1) {
+ bool timedout = ktime_after(ktime_get(), timeout);
+
+ if (!(sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask))
+ break;
+ if (timedout) {
pr_err("%s: Reset 0x%x never completed.\n",
mmc_hostname(host->mmc), (int)mask);
sdhci_dumpregs(host);
@@ -1608,9 +1612,13 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)

/* Wait max 20 ms */
timeout = ktime_add_ms(ktime_get(), 20);
- while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
- & SDHCI_CLOCK_INT_STABLE)) {
- if (ktime_after(ktime_get(), timeout)) {
+ while (1) {
+ bool timedout = ktime_after(ktime_get(), timeout);
+
+ clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+ if (clk & SDHCI_CLOCK_INT_STABLE)
+ break;
+ if (timedout) {
pr_err("%s: Internal clock never stabilised.\n",
mmc_hostname(host->mmc));
sdhci_dumpregs(host);
--
2.17.1