linux-kernel - Re: [PATCH v3 3/3] drm/tidss: Add support for AM62L display subsystem

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Message-ID: <74ffed53-d6df-437a-b997-62fef3ee4d00@ideasonboard.com>
Date: Thu, 13 Mar 2025 11:41:22 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Devarsh Thakkar <devarsht@...com>
Cc: praneeth@...com, vigneshr@...com, aradhya.bhatia@...ux.dev,
 s-jain1@...com, r-donadkar@...com, j-choudhary@...com, h-shenoy@...com,
 jyri.sarha@....fi, airlied@...il.com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, dri-devel@...ts.freedesktop.org,
 simona@...ll.ch, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org
Subject: Re: [PATCH v3 3/3] drm/tidss: Add support for AM62L display subsystem

Hi,

On 06/03/2025 15:29, Devarsh Thakkar wrote:
> Enable display for AM62L DSS [1] which supports only a single display
> pipeline using a single overlay manager, single video port and a single
> video lite pipeline which does not support scaling.
> 
> The output of video port is routed to SoC boundary via DPI interface and
> the DPI signals from the video port are also routed to DSI Tx controller
> present within the SoC.
> 
> [1]: Section 11.7 (Display Subsystem and Peripherals)
> Link : https://www.ti.com/lit/pdf/sprujb4
> 
> Signed-off-by: Devarsh Thakkar <devarsht@...com>
> ---
> V3:
> - Rebase on top of
>    0002-drm-tidss-Update-infra-to-support-DSS7-cut-down-vers.patch
> - Use the generic "tidss_am65x_common_regs" as common reg space
>    instead of creating a new one.
> 
> V2:
> - Add separate common reg space for AM62L
> - Add separate irq enable/disable/read/clear helpers for AM62L
> - Use separate helper function for setting overlay attributes
> - Drop Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
>    due to additional changes made in V2.
> 
>   drivers/gpu/drm/tidss/tidss_dispc.c | 46 +++++++++++++++++++++++++++++
>   drivers/gpu/drm/tidss/tidss_dispc.h |  2 ++
>   drivers/gpu/drm/tidss/tidss_drv.c   |  1 +
>   3 files changed, 49 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index 9b46403dbb0c..0ca0c2106715 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -440,6 +440,47 @@ const struct dispc_features dispc_am62a7_feats = {
>   	.vid_order = {1, 0},
>   };
>   
> +const struct dispc_features dispc_am62l_feats = {
> +	.max_pclk_khz = {
> +		[DISPC_VP_DPI] = 165000,
> +	},
> +
> +	.subrev = DISPC_AM62L,
> +
> +	.common = "common",
> +	.common_regs = tidss_am65x_common_regs,
> +
> +	.num_vps = 1,
> +	.vp_name = { "vp1" },
> +	.ovr_name = { "ovr1" },
> +	.vpclk_name =  { "vp1" },
> +	.vp_bus_type = { DISPC_VP_DPI },
> +
> +	.vp_feat = { .color = {
> +			.has_ctm = true,
> +			.gamma_size = 256,
> +			.gamma_type = TIDSS_GAMMA_8BIT,
> +		},
> +	},
> +
> +	.num_planes = 2,
> +
> +	.vid_info = {
> +		{
> +			.vid_name = "vid",
> +			.vid_lite = false,
> +			.is_present = false,
> +		},
> +		{
> +			.vid_name = "vidl1",
> +			.vid_lite = true,
> +			.is_present = true,
> +		}
> +	},

I don't think this is a good idea. Now you have tidss->num_planes 1, and 
feat->num_planes 2. It get's very confusing.

The naming is also mixed up. You have "vid_info" field, which has 
"plane_info" entries...

My suggestion is to have entries in vid_info only for the instantiated 
vids, like this:

struct vid_info {
	u32 hw_id;
	const char *name; /* Should match dt reg names */
	bool is_lite;
};

While at it, let's change the num_planes name in the feat struct too, to 
num_vids. This will also highlight all the places in the code that use 
the vid structs.

For AM62L it would be:

.num_vids = 1,

{
	.hw_id = 1,
	.name = "vidl1",
	.is_lite = true,
}

  Tomi