linux-kernel - Re: [PATCH] drm/bridge: tc358767: Support input format negotiation hook

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Date:   Mon, 6 Nov 2023 13:38:00 +0100
From:   Sam Ravnborg <sam@...nborg.org>
To:     Aradhya Bhatia <a-bhatia1@...com>
Cc:     Tomi Valkeinen <tomba@...nel.org>, Jyri Sarha <jyri.sarha@....fi>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Francesco Dolcini <francesco@...cini.it>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        DRI Development List <dri-devel@...ts.freedesktop.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Devarsh Thakkar <devarsht@...com>,
        Jayesh Choudhary <j-choudhary@...com>
Subject: Re: [PATCH] drm/bridge: tc358767: Support input format negotiation
 hook

Hi Aradhya,

On Tue, Oct 31, 2023 at 12:58:46AM +0530, Aradhya Bhatia wrote:
> With new connector model, tc358767 will not create the connector, when
> DRM_BRIDGE_ATTACH_NO_CONNECTOR is set and display-controller driver will
> rely on format negotiation to setup the encoder format.
> 
> Add the missing input-format negotiation hook in the
> drm_bridge_funcs to complete DRM_BRIDGE_ATTACH_NO_CONNECTOR support.
> 
> Input format is selected to MEDIA_BUS_FMT_RGB888_1X24 as default, as is
> the case with older model.
> 
> Reported-by: Jan Kiszka <jan.kiszka@...mens.com>
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
> 
> Notes:
> 
>   * Since I do not have hardware with me, this was just build tested. I would
>     appreciate it if someone could test and review it, especically somebody, who
>     uses the bridge for DPI/DSI to eDP format conversion.
> 
>   * The Toshiba TC358767 bridge is not enabled in arm64 defconfig by default,
>     when it should be. Hence, I sent a quick patch[0] earlier.
> 
> [0]: https://lore.kernel.org/all/20231030152834.18450-1-a-bhatia1@ti.com/
> 
>  drivers/gpu/drm/bridge/tc358767.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index ef2e373606ba..0affcefdeb1c 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -1751,6 +1751,30 @@ tc_dpi_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>  	return input_fmts;
>  }
>  
> +static u32 *
> +tc_edp_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
> +				 struct drm_bridge_state *bridge_state,
> +				 struct drm_crtc_state *crtc_state,
> +				 struct drm_connector_state *conn_state,
> +				 u32 output_fmt,
> +				 unsigned int *num_input_fmts)
> +{
> +	u32 *input_fmts;
> +
> +	*num_input_fmts = 0;
> +
> +	input_fmts = kcalloc(MAX_INPUT_SEL_FORMATS, sizeof(*input_fmts),
> +			     GFP_KERNEL);
> +	if (!input_fmts)
> +		return NULL;
> +
> +	/* This is the DSI/DPI-end bus format */
> +	input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
> +	*num_input_fmts = 1;
> +
> +	return input_fmts;
> +}

You could benefit from using the helper:
drm_atomic_helper_bridge_propagate_bus_fmt()

	Sam