Re: [PATCH] clk: ti: clkctrl: Fix failed to enable error with double udelay timeout

[Keerthy <j-keerthy@ti.com>]

On 30/09/19 9:10 PM, Tony Lindgren wrote:
> Commit 3d8598fb9c5a ("clk: ti: clkctrl: use fallback udelay approach if
> timekeeping is suspended") added handling for cases when timekeeping is
> suspended. But looks like we can still get occasional "failed to enable"
> errors on the PM runtime resume path with udelay() returning faster than
> expected.
> 
> With ti-sysc interconnect target module driver this leads into device
> failure with PM runtime failing with "failed to enable" clkctrl error.
> 
> Let's fix the issue with a delay of two times the desired delay as in
> often done for udelay() to account for the inaccuracy.

Tested for DS0 and rtc+ddr modes on am43 and ds0 on am33.

Tested-by: Keerthy <j-keerthy@ti.com>

> 
> Fixes: 3d8598fb9c5a ("clk: ti: clkctrl: use fallback udelay approach if timekeeping is suspended")
> Cc: Keerthy <j-keerthy@ti.com>
> Cc: Tero Kristo <t-kristo@ti.com>
> Signed-off-by: Tony Lindgren <tony@atomide.com>
> ---
>   drivers/clk/ti/clkctrl.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/ti/clkctrl.c b/drivers/clk/ti/clkctrl.c
> --- a/drivers/clk/ti/clkctrl.c
> +++ b/drivers/clk/ti/clkctrl.c
> @@ -100,11 +100,12 @@ static bool _omap4_is_timeout(union omap4_timeout *time, u32 timeout)
>   	 * can be from a timer that requires pm_runtime access, which
>   	 * will eventually bring us here with timekeeping_suspended,
>   	 * during both suspend entry and resume paths. This happens
> -	 * at least on am43xx platform.
> +	 * at least on am43xx platform. Account for flakeyness
> +	 * with udelay() by multiplying the timeout value by 2.
>   	 */
>   	if (unlikely(_early_timeout || timekeeping_suspended)) {
>   		if (time->cycles++ < timeout) {
> -			udelay(1);
> +			udelay(1 * 2);
>   			return false;
>   		}
>   	} else {
>