linux-kernel - Re: [PATCH] soc: qcom: rpmh: Dirt can only make you dirtier, not cleaner

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Message-ID: <20200418161557.GF199755@google.com>
Date:   Sat, 18 Apr 2020 09:15:57 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     bjorn.andersson@...aro.org, agross@...nel.org, swboyd@...omium.org,
        mkshah@...eaurora.org, Evan Green <evgreen@...omium.org>,
        Srinivas Rao L <lsrao@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soc: qcom: rpmh: Dirt can only make you dirtier, not
 cleaner

On Fri, Apr 17, 2020 at 02:15:47PM -0700, Douglas Anderson wrote:
> Adding an item into the cache should never be able to make the cache
> cleaner.  Use "|=" rather than "=" to update the dirty flag.
> 
> Fixes: bb7000677a1b ("soc: qcom: rpmh: Update dirty flag only when data changes")
> Reported-by: Stephen Boyd <swboyd@...omium.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>  drivers/soc/qcom/rpmh.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> index 3abbb08cd6e1..d1626a1328d7 100644
> --- a/drivers/soc/qcom/rpmh.c
> +++ b/drivers/soc/qcom/rpmh.c
> @@ -151,10 +151,10 @@ static struct cache_req *cache_rpm_request(struct rpmh_ctrlr *ctrlr,
>  		break;
>  	}
>  
> -	ctrlr->dirty = (req->sleep_val != old_sleep_val ||
> -			req->wake_val != old_wake_val) &&
> -			req->sleep_val != UINT_MAX &&
> -			req->wake_val != UINT_MAX;
> +	ctrlr->dirty |= (req->sleep_val != old_sleep_val ||
> +			 req->wake_val != old_wake_val) &&
> +			 req->sleep_val != UINT_MAX &&
> +			 req->wake_val != UINT_MAX;
>  
>  unlock:
>  	spin_unlock_irqrestore(&ctrlr->cache_lock, flags);

Reviewed-by: Matthias Kaehlcke <mka@...omium.org>