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

[alek . du]

From: Alek Du <alek...@intel.com>

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")
Cc: sta...@vger.kernel.org      # v4.12+
Signed-off-by: Alek Du <alek...@intel.com>
---
 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