linux-kernel - Re: [RFC PATCH 03/10] drm/mipi-dsi: add API for manual control over the DSI link power state

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Date:   Thu, 19 Oct 2023 11:26:16 +0200
From:   Maxime Ripard <mripard@...nel.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Douglas Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Marek Vasut <marex@...x.de>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [RFC PATCH 03/10] drm/mipi-dsi: add API for manual control over
 the DSI link power state

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.
> 
> Introduce API that allows DSI bridges / panels to control the DSI host
> power up state.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>  drivers/gpu/drm/drm_mipi_dsi.c | 31 +++++++++++++++++++++++++++++++
>  include/drm/drm_mipi_dsi.h     | 29 +++++++++++++++++++++++++----
>  2 files changed, 56 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.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);
>  
> +bool mipi_dsi_host_power_control_available(struct mipi_dsi_host *host)
> +{
> +	const struct mipi_dsi_host_ops *ops = 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 = 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 = 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