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SubjectRe: [PATCH] soc: qcom: rpmh-rsc: Don't use ktime for timeout in write_tcs_reg_sync()
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Reviewed-by: Maulik Shah <mkshah@codeaurora.org>

Thanks,
Maulik

On 5/28/2020 8:18 PM, Douglas Anderson wrote:
> The write_tcs_reg_sync() may be called after timekeeping is suspended
> so it's not OK to use ktime. The readl_poll_timeout_atomic() macro
> implicitly uses ktime. This was causing a warning at suspend time.
>
> Change to just loop 1000000 times with a delay of 1 us between loops.
> This may give a timeout of more than 1 second but never less and is
> safe even if timekeeping is suspended.
>
> NOTE: I don't have any actual evidence that we need to loop here.
> It's possibly that all we really need to do is just read the value
> back to ensure that the pipes are cleaned and the looping/comparing is
> totally not needed. I never saw the loop being needed in my tests.
> However, the loop shouldn't hurt.
>
> Fixes: 91160150aba0 ("soc: qcom: rpmh-rsc: Timeout after 1 second in write_tcs_reg_sync()")
> Reported-by: Maulik Shah <mkshah@codeaurora.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> drivers/soc/qcom/rpmh-rsc.c | 18 +++++++++++++-----
> 1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index 076fd27f3081..906778e2c1fa 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -175,13 +175,21 @@ static void write_tcs_reg(const struct rsc_drv *drv, int reg, int tcs_id,
> static void write_tcs_reg_sync(const struct rsc_drv *drv, int reg, int tcs_id,
> u32 data)
> {
> - u32 new_data;
> + int i;
>
> writel(data, tcs_reg_addr(drv, reg, tcs_id));
> - if (readl_poll_timeout_atomic(tcs_reg_addr(drv, reg, tcs_id), new_data,
> - new_data == data, 1, USEC_PER_SEC))
> - pr_err("%s: error writing %#x to %d:%#x\n", drv->name,
> - data, tcs_id, reg);
> +
> + /*
> + * Wait until we read back the same value. Use a counter rather than
> + * ktime for timeout since this may be called after timekeeping stops.
> + */
> + for (i = 0; i < USEC_PER_SEC; i++) {
> + if (readl(tcs_reg_addr(drv, reg, tcs_id)) == data)
> + return;
> + udelay(1);
> + }
> + pr_err("%s: error writing %#x to %d:%#x\n", drv->name,
> + data, tcs_id, reg);
> }
>
> /**

--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

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