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SubjectRe: [RFT PATCH v2 06/10] drivers: qcom: rpmh-rsc: Comment tcs_is_free() + warn if state mismatch
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Hi,

On 3/12/2020 4:43 AM, Douglas Anderson wrote:
> tcs_is_free() had two checks in it: does the software think that the
> TCS is free and does the hardware think that the TCS is free. Let's
> comment this and also add a warning in the case that software and
> hardware disagree, at least for ACTIVE_ONLY TCS.
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---
>
> Changes in v2:
> - Comment tcs_is_free() new for v2; replaces old patch 6.
>
> drivers/soc/qcom/rpmh-rsc.c | 23 +++++++++++++++++++++--
> 1 file changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index 9d2669cbd994..93f5d1fb71ca 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -181,8 +181,27 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,
> */
> static bool tcs_is_free(struct rsc_drv *drv, int tcs_id)
> {
> - return !test_bit(tcs_id, drv->tcs_in_use) &&
> - read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id);
> + /* If software thinks it's in use then it's definitely in use */
> + if (test_bit(tcs_id, drv->tcs_in_use))
> + return false;
> +
> + /* If hardware agrees it's free then it's definitely free */
> + if (read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id) != 0)
> + return true;
> +
> + /*
> + * If we're here then software and hardware disagree about whether
> + * the TCS is free. Software thinks it is free and hardware thinks
> + * it is not.
> + *
> + * Maybe this should be a warning in all cases, but it's almost
> + * certainly a warning for the ACTIVE_TCS where nobody else should
> + * be doing anything else behind our backs. For now we'll just
> + * warn there and then still return that we're in use.
> + */
> + WARN(drv->tcs[tcs_id].type == ACTIVE_TCS,
> + "Driver thought TCS was free but HW reported busy\n");
This warning can come for borrowed WAKE_TCS as well.
> + return false;
> }

We have a patch on downstream variant to optimize this by only checking
tcs_in_use flag (SW check) and HW check is removed.

 static bool tcs_is_free(struct rsc_drv *drv, int tcs_id)
 {
-       return !test_bit(tcs_id, drv->tcs_in_use) &&
-              read_tcs_reg(drv, RSC_DRV_STATUS, tcs_id, 0);
+       return !test_bit(tcs_id, drv->tcs_in_use);
 }

With this we are good and don't require to put above warning as well.

if you want me to upload, i can post it and then you can drop this
change from your series.

Or if you want to modify it as above and keep in this series i am ok.

Thanks,
Maulik

>
> /**

--
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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