linux-kernel - Re: [PATCH v1 20/35] drm/vc4: vec: Switch for common modes

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Date:   Fri, 29 Jul 2022 20:12:07 +0200
From:   Mateusz Kwiatkowski <kfyatek@...il.com>
To:     Maxime Ripard <maxime@...no.tech>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Jerome Brunet <jbrunet@...libre.com>,
        Samuel Holland <samuel@...lland.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Kevin Hilman <khilman@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Maxime Ripard <mripard@...nel.org>
Cc:     linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Phil Elwell <phil@...pberrypi.com>,
        linux-arm-kernel@...ts.infradead.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-amlogic@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
        Dom Cobley <dom@...pberrypi.com>
Subject: Re: [PATCH v1 20/35] drm/vc4: vec: Switch for common modes

Hi Maxime,

I'm just noting that the modelines you defined in drm_modes.c are 
different to the ones you're removing here.

The horizontal sync differences probably doesn't matter too much, VC4 
uses those only as a hint anyway and generates sync autonomously, so the 
slight differences will only cause the image to slightly shift horizontally.

But you're also changing the 480i vertical sync (vsync_start is now 488 
instead of 487, etc.). Are you sure that this won't break anything? This 
will probably shift the image by 1 line (which for the 480i might 
actually mean going out of spec), and I _think_ it might control the odd 
vs. even field first modes on some drivers. I won't be able to test this 
before Monday, but I'm just pointing out the potential issue.

BTW, I've seen a similar thing in the sun4i driver changes (patch 32/35) 
and the differences in vertical sync are even more dramatic. It's 
entirely possible that the current timings in sun4i are broken and the 
new ones are correct (the new ones certainly look saner to me), but I'd 
double-check if that driver does not have any quirks that would 
_require_ such weird settings.

Best regards,
Mateusz Kwiatkowski

W dniu 29.07.2022 o 18:35, Maxime Ripard pisze:
> Now that the core has a definition for the 525 and 625 lines analog TV
> modes, let's switch to it for vc4.
>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
>
> diff --git a/drivers/gpu/drm/vc4/vc4_vec.c b/drivers/gpu/drm/vc4/vc4_vec.c
> index 8f30a530b2d5..255bba563fce 100644
> --- a/drivers/gpu/drm/vc4/vc4_vec.c
> +++ b/drivers/gpu/drm/vc4/vc4_vec.c
> @@ -224,38 +224,24 @@ static const struct debugfs_reg32 vec_regs[] = {
>   	VC4_REG32(VEC_DAC_MISC),
>   };
>   
> -static const struct drm_display_mode ntsc_mode = {
> -	DRM_MODE("720x480", DRM_MODE_TYPE_DRIVER, 13500,
> -		 720, 720 + 14, 720 + 14 + 64, 720 + 14 + 64 + 60, 0,
> -		 480, 480 + 7, 480 + 7 + 6, 525, 0,
> -		 DRM_MODE_FLAG_INTERLACE)
> -};
> -
> -static const struct drm_display_mode pal_mode = {
> -	DRM_MODE("720x576", DRM_MODE_TYPE_DRIVER, 13500,
> -		 720, 720 + 20, 720 + 20 + 64, 720 + 20 + 64 + 60, 0,
> -		 576, 576 + 4, 576 + 4 + 6, 625, 0,
> -		 DRM_MODE_FLAG_INTERLACE)
> -};
> -
>   static const struct vc4_vec_tv_mode vc4_vec_tv_modes[] = {
>   	[VC4_VEC_TV_MODE_NTSC] = {
> -		.mode = &ntsc_mode,
> +		.mode = &drm_mode_480i,
>   		.config0 = VEC_CONFIG0_NTSC_STD | VEC_CONFIG0_PDEN,
>   		.config1 = VEC_CONFIG1_C_CVBS_CVBS,
>   	},
>   	[VC4_VEC_TV_MODE_NTSC_J] = {
> -		.mode = &ntsc_mode,
> +		.mode = &drm_mode_480i,
>   		.config0 = VEC_CONFIG0_NTSC_STD,
>   		.config1 = VEC_CONFIG1_C_CVBS_CVBS,
>   	},
>   	[VC4_VEC_TV_MODE_PAL] = {
> -		.mode = &pal_mode,
> +		.mode = &drm_mode_576i,
>   		.config0 = VEC_CONFIG0_PAL_BDGHI_STD,
>   		.config1 = VEC_CONFIG1_C_CVBS_CVBS,
>   	},
>   	[VC4_VEC_TV_MODE_PAL_M] = {
> -		.mode = &pal_mode,
> +		.mode = &drm_mode_576i,
>   		.config0 = VEC_CONFIG0_PAL_BDGHI_STD,
>   		.config1 = VEC_CONFIG1_C_CVBS_CVBS | VEC_CONFIG1_CUSTOM_FREQ,
>   		.custom_freq = 0x223b61d1,
>