On 10/28/20 7:39 PM, Chunyan Zhang wrote:
> From: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>
>
> After changing to check busy bit for the previous loading operation instead
> of the current one, for most of cases, the busy bit is not set for the
> first time of read, so there's no need to check so frequently, so this
> patch use usleep_range() to replace cpu_relax() to avoid busy loop.
>
> Also this patch change the max times to 11 which would be enough, since
> according to the specification, the busy bit would be set after a new
> loading operation and last 2 or 3 RTC clock cycles (about 60us~92us).
>
> Fixes: 477603467009 ("watchdog: Add Spreadtrum watchdog driver")
> Original-by: Lingling Xu <ling_ling.xu@xxxxxxxxxx>
> Signed-off-by: Chunyan Zhang <chunyan.zhang@xxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> drivers/watchdog/sprd_wdt.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/watchdog/sprd_wdt.c b/drivers/watchdog/sprd_wdt.c
> index b9b1daa9e2a4..e8097551dfcd 100644
> --- a/drivers/watchdog/sprd_wdt.c
> +++ b/drivers/watchdog/sprd_wdt.c
> @@ -53,7 +53,7 @@
>
> #define SPRD_WDT_CNT_HIGH_SHIFT 16
> #define SPRD_WDT_LOW_VALUE_MASK GENMASK(15, 0)
> -#define SPRD_WDT_LOAD_TIMEOUT 1000
> +#define SPRD_WDT_LOAD_TIMEOUT 11
>
> struct sprd_wdt {
> void __iomem *base;
> @@ -109,15 +109,17 @@ static int sprd_wdt_load_value(struct sprd_wdt *wdt, u32 timeout,
> u32 prtmr_step = pretimeout * SPRD_WDT_CNT_STEP;
>
> /*
> - * Waiting the load value operation done,
> - * it needs two or three RTC clock cycles.
> + * Checking busy bit to make sure the previous loading operation is
> + * done. According to the specification, the busy bit would be set
> + * after a new loading operation and last 2 or 3 RTC clock
> + * cycles (about 60us~92us).
> */
> do {
> val = readl_relaxed(wdt->base + SPRD_WDT_INT_RAW);
> if (!(val & SPRD_WDT_LD_BUSY_BIT))
> break;
>
> - cpu_relax();
> + usleep_range(10, 100);
> } while (delay_cnt++ < SPRD_WDT_LOAD_TIMEOUT);
>
> if (delay_cnt >= SPRD_WDT_LOAD_TIMEOUT)
>
