linux-kernel - Re: [PATCH v3 07/10] drivers: qcom: rpmh-rsc: tcs_is_free() can just check tcs_in

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Date:   Wed, 8 Apr 2020 16:55:56 +0530
From:   Maulik Shah <mkshah@...eaurora.org>
To:     Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     mka@...omium.org, Lina Iyer <ilina@...eaurora.org>,
        Rajendra Nayak <rnayak@...eaurora.org>, swboyd@...omium.org,
        evgreen@...omium.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/10] drivers: qcom: rpmh-rsc: tcs_is_free() can just
 check tcs_in_use

Hi,

Reviewed-by: Maulik Shah <mkshah@...eaurora.org>
Tested-by: Maulik Shah <mkshah@...eaurora.org>

Thanks,
Maulik

On 4/8/2020 5:20 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.  I
> couldn't figure out in which case the hardware could think that a TCS
> was in-use but software thought it was free.  Apparently there is no
> case and the extra check can be removed.  This apparently has already
> been done in a downstream patch.
>
> Suggested-by: Maulik Shah <mkshah@...eaurora.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
> Changes in v3:
> - Replace ("...warn if state mismatch") w/ ("...just check tcs_in_use")
>
> Changes in v2:
> - Comment tcs_is_free() new for v2; replaces old patch 6.
>
>   drivers/soc/qcom/rpmh-rsc.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/soc/qcom/rpmh-rsc.c b/drivers/soc/qcom/rpmh-rsc.c
> index 84ae3e514eee..9502e7ea96be 100644
> --- a/drivers/soc/qcom/rpmh-rsc.c
> +++ b/drivers/soc/qcom/rpmh-rsc.c
> @@ -177,7 +177,6 @@ static void write_tcs_reg_sync(struct rsc_drv *drv, int reg, int tcs_id,
>    * @tcs_id: The global ID of this TCS.
>    *
>    * Returns true if nobody has claimed this TCS (by setting tcs_in_use).
> - * If the TCS looks free, checks that the hardware agrees.
>    *
>    * Must be called with the drv->lock held or the tcs_lock for the TCS being
>    * tested. If only the tcs_lock is held then it is possible that this
> @@ -188,8 +187,7 @@ 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);
> +	return !test_bit(tcs_id, drv->tcs_in_use);
>   }
>   
>   /**

-- 
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