Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210421001908.813625-1-drinkcat@chromium.org> <20210421081831.v12.3.I3af068abe30c9c85cabc4486385c52e56527a509@changeid>
In-Reply-To: <20210421081831.v12.3.I3af068abe30c9c85cabc4486385c52e56527a509@changeid>
From:   Nicolas Boichat <drinkcat@chromium.org>
Date:   Wed, 21 Apr 2021 12:00:24 +0800
Message-ID: <CANMq1KBfg1SKM1iC+EUXjCiA-f9p=JSBvkp3h3eygH2aZfCAng@mail.gmail.com>
Subject: Re: [PATCH v12 3/4] drm/panfrost: devfreq: Disable devfreq when
 num_supplies > 1
To:     Rob Herring <robh@kernel.org>, Steven Price <steven.price@arm.com>,
        Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Cc:     Fei Shao <fshao@chromium.org>, Hsin-Yi Wang <hsinyi@chromium.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Kristian Kristensen <hoegsberg@chromium.org>,
        Tomeu Vizoso <tomeu.vizoso@collabora.com>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        lkml <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Argh sorry I messed up the rebase and this doesn't even build...

I'll send v13.

On Wed, Apr 21, 2021 at 8:19 AM Nicolas Boichat <drinkcat@chromium.org> wrote:
>
> GPUs with more than a single regulator (e.g. G72 on MT8183) will
> require platform-specific handling for devfreq, for 2 reasons:
>  1. The opp core (drivers/opp/core.c:_generic_set_opp_regulator)
>     does not support multiple regulators, so we'll need custom
>     handlers.
>  2. Generally, platforms with 2 regulators have platform-specific
>     constraints on how the voltages should be set (e.g.
>     minimum/maximum voltage difference between them), so we
>     should not just create generic handlers that simply
>     change the voltages without taking care of those constraints.
>
> Disable devfreq for now on those GPUs.
>
> Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
> Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
> Reviewed-by: Steven Price <steven.price@arm.com>
> ---
>
> (no changes since v9)
>
> Changes in v9:
>  - Explain why devfreq needs to be disabled for GPUs with >1
>    regulators.
>
> Changes in v8:
>  - Use DRM_DEV_INFO instead of ERROR
>
> Changes in v7:
>  - Fix GPU ID in commit message
>
> Changes in v6:
>  - devfreq: New change
>
>  drivers/gpu/drm/panfrost/panfrost_devfreq.c | 16 +++++++++++++---
>  1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/panfrost/panfrost_devfreq.c b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> index 47d27e54a34f..aca3bb9a12e4 100644
> --- a/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> +++ b/drivers/gpu/drm/panfrost/panfrost_devfreq.c
> @@ -92,9 +92,19 @@ int panfrost_devfreq_init(struct panfrost_device *pfdev)
>         struct thermal_cooling_device *cooling;
>         struct panfrost_devfreq *pfdevfreq = &pfdev->pfdevfreq;
>
> -       ret = devm_pm_opp_set_regulators(dev, pfdev->comp->supply_names,
> -                                        pfdev->comp->num_supplies);
> -       if (ret) {
> +       if (pfdev->comp->num_supplies > 1) {
> +               /*
> +                * GPUs with more than 1 supply require platform-specific handling:
> +                * continue without devfreq
> +                */
> +               DRM_DEV_INFO(dev, "More than 1 supply is not supported yet\n");
> +               return 0;
> +       }
> +
> +       opp_table = dev_pm_opp_set_regulators(dev, pfdev->comp->supply_names,
> +                                             pfdev->comp->num_supplies);
> +       if (IS_ERR(opp_table)) {
> +               ret = PTR_ERR(opp_table);
>                 /* Continue if the optional regulator is missing */
>                 if (ret != -ENODEV) {
>                         DRM_DEV_ERROR(dev, "Couldn't set OPP regulators\n");
> --
> 2.31.1.368.gbe11c130af-goog
>