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Subject: Re: [PATCH v17 2/6] soc: qcom: rpmh: Update dirty flag only when data changes
From:   Stephen Boyd <swboyd@chromium.org>
Cc:     linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        agross@kernel.org, mka@chromium.org, rnayak@codeaurora.org,
        ilina@codeaurora.org, lsrao@codeaurora.org,
        Maulik Shah <mkshah@codeaurora.org>
To:     Maulik Shah <mkshah@codeaurora.org>, bjorn.andersson@linaro.org,
        dianders@chromium.org, evgreen@chromium.org
Date:   Thu, 16 Apr 2020 16:58:57 -0700
Message-ID: <158708153779.132238.7823999141480422982@swboyd.mtv.corp.google.com>
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Quoting Maulik Shah (2020-04-12 07:50:00)
> diff --git a/drivers/soc/qcom/rpmh.c b/drivers/soc/qcom/rpmh.c
> index eb0ded0..03630ae 100644
> --- a/drivers/soc/qcom/rpmh.c
> +++ b/drivers/soc/qcom/rpmh.c
> @@ -133,26 +134,27 @@ static struct cache_req *cache_rpm_request(struct r=
pmh_ctrlr *ctrlr,
> =20
>         req->addr =3D cmd->addr;
>         req->sleep_val =3D req->wake_val =3D UINT_MAX;
> -       INIT_LIST_HEAD(&req->list);
>         list_add_tail(&req->list, &ctrlr->cache);
> =20
>  existing:
> +       old_sleep_val =3D req->sleep_val;
> +       old_wake_val =3D req->wake_val;
> +
>         switch (state) {
>         case RPMH_ACTIVE_ONLY_STATE:
> -               if (req->sleep_val !=3D UINT_MAX)
> -                       req->wake_val =3D cmd->data;
> -               break;
>         case RPMH_WAKE_ONLY_STATE:
>                 req->wake_val =3D cmd->data;
>                 break;
>         case RPMH_SLEEP_STATE:
>                 req->sleep_val =3D cmd->data;
>                 break;
> -       default:
> -               break;
>         }
> =20
> -       ctrlr->dirty =3D true;
> +       ctrlr->dirty =3D (req->sleep_val !=3D old_sleep_val ||
> +                       req->wake_val !=3D old_wake_val) &&
> +                       req->sleep_val !=3D UINT_MAX &&
> +                       req->wake_val !=3D UINT_MAX;

Can this change ctrl->dirty from true to false? I'm worried that we need
to make this a saturating assignment instead of an assignment.

	ctrl->dirty =3D ctrl->dirty || (req->sleep_val !=3D .. );

> +
>  unlock:
>         spin_unlock_irqrestore(&ctrlr->cache_lock, flags);
>