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Date:   Thu, 19 Oct 2023 11:26:16 +0200
From:   Maxime Ripard <mripard@kernel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     Dave Stevenson <dave.stevenson@raspberrypi.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Douglas Anderson <dianders@chromium.org>,
        Rob Clark <robdclark@gmail.com>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Sean Paul <sean@poorly.run>,
        Marijn Suijten <marijn.suijten@somainline.org>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Jessica Zhang <quic_jesszhan@quicinc.com>,
        Marek Vasut <marex@denx.de>, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        freedreno@lists.freedesktop.org
Subject: Re: [RFC PATCH 03/10] drm/mipi-dsi: add API for manual control over
 the DSI link power state
Message-ID: <7e4ak4e77fp5dat2aopyq3g4wnqu3tt7di7ytdr3dvgjviyhrd@vqiqx6iso6vg>
References: <20231016165355.1327217-1-dmitry.baryshkov@linaro.org>
 <20231016165355.1327217-4-dmitry.baryshkov@linaro.org>
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On Mon, Oct 16, 2023 at 07:53:48PM +0300, Dmitry Baryshkov wrote:
> The MIPI DSI links do not fully fall into the DRM callbacks model.

Explaining why would help

> The drm_bridge_funcs abstraction.

Is there a typo or missing words?

> Instead of having just two states (off and on) the DSI hosts have
> separate LP-11 state. In this state the host is on, but the video
> stream is not yet enabled.
>=20
> Introduce API that allows DSI bridges / panels to control the DSI host
> power up state.
>=20
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 31 +++++++++++++++++++++++++++++++
>  include/drm/drm_mipi_dsi.h     | 29 +++++++++++++++++++++++++----
>  2 files changed, 56 insertions(+), 4 deletions(-)
>=20
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_ds=
i.c
> index 14201f73aab1..c467162cb7d8 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -428,6 +428,37 @@ int devm_mipi_dsi_attach(struct device *dev,
>  }
>  EXPORT_SYMBOL_GPL(devm_mipi_dsi_attach);
> =20
> +bool mipi_dsi_host_power_control_available(struct mipi_dsi_host *host)
> +{
> +	const struct mipi_dsi_host_ops *ops =3D host->ops;
> +
> +	return ops && ops->power_up;
> +}
> +EXPORT_SYMBOL_GPL(mipi_dsi_host_power_control_available);
> +
> +int mipi_dsi_host_power_up(struct mipi_dsi_host *host)
> +{
> +	const struct mipi_dsi_host_ops *ops =3D host->ops;
> +
> +	if (!mipi_dsi_host_power_control_available(host))
> +		return -EOPNOTSUPP;
> +
> +	return ops->power_up ? ops->power_up(host) : 0;
> +}
> +EXPORT_SYMBOL_GPL(mipi_dsi_host_power_up);
> +
> +void mipi_dsi_host_power_down(struct mipi_dsi_host *host)
> +{
> +	const struct mipi_dsi_host_ops *ops =3D host->ops;
> +
> +	if (!mipi_dsi_host_power_control_available(host))
> +		return;
> +
> +	if (ops->power_down)
> +		ops->power_down(host);
> +}
> +EXPORT_SYMBOL_GPL(mipi_dsi_host_power_down);
> +

If this API is supposed to be used by DSI devices, it should probably
take a mipi_dsi_device pointer as a parameter?

We should probably make sure it hasn't been powered on already too?

Maxime