linux-kernel - Re: [PATCH v6 3/8] drm/bridge: mhdp8546: Add minimal format negotiation

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Message-ID: <db9b4117-b030-49a7-3732-2fc39d089ee2@ideasonboard.com>
Date:   Fri, 12 May 2023 12:15:57 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Aradhya Bhatia <a-bhatia1@...com>, 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>,
        Rahul T R <r-ravikumar@...com>,
        Swapnil Jakhade <sjakhade@...ence.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Francesco Dolcini <francesco@...cini.it>
Cc:     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 v6 3/8] drm/bridge: mhdp8546: Add minimal format
 negotiation

On 09/05/2023 12:30, Aradhya Bhatia wrote:
> From: Nikhil Devshatwar <nikhil.nd@...com>
> 
> With new connector model, mhdp bridge will not create the connector and
> SoC driver will rely on format negotiation to setup the encoder format.
> 
> Support minimal format negotiations hooks in the drm_bridge_funcs.
> Complete format negotiation can be added based on EDID data.
> This patch adds the minimal required support to avoid failure
> after moving to new connector model.
> 
> Signed-off-by: Nikhil Devshatwar <nikhil.nd@...com>
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...com>

You need to add your SoB to this and the other patches.

> ---
> 
> Notes:
> 
>      changes from v1:
>      * cosmetic fixes, commit message update.
> 
>      changes from v5:
>      * dropped the default_bus_format variable and directly assigned
>        MEDIA_BUS_FMT_RGB121212_1X36 to input_fmts.
> 
>   .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 25 +++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> index f6822dfa3805..623e4235c94f 100644
> --- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> +++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
> @@ -2146,6 +2146,30 @@ cdns_mhdp_bridge_atomic_reset(struct drm_bridge *bridge)
>   	return &cdns_mhdp_state->base;
>   }
>   
> +static u32 *cdns_mhdp_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;
> +
> +	if (output_fmt != MEDIA_BUS_FMT_FIXED)
> +		return NULL;

The tfp410 and sii902x drivers don't have the above check. Why does mhdp 
need it? Or the other way, why don't tfp410 and sii902x need it?

I guess at the moment we always do get MEDIA_BUS_FMT_FIXED as the out 
fmt (in all three bridge drivers), don't we?

  Tomi