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

Adrian Hunter
2018-12-05T11:16:27Z

On 5/12/18 5:14 AM, Du, Alek wrote:
>>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+

Acked-by: Adrian Hunter <adrian.hunter@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);
>