linux-kernel - Re: [PATCH v2] drm/rcar-du: dsi: Handle both DRM_MODE_FLAG_N.SYNC and !DRM_MODE_FLAG

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Message-ID: <874ca23f-c50e-49ae-be2b-eb6b9cf2b068@ideasonboard.com>
Date: Thu, 4 Dec 2025 14:58:44 +0200
From: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
To: Marek Vasut <marek.vasut+renesas@...lbox.org>,
 dri-devel@...ts.freedesktop.org
Cc: David Airlie <airlied@...il.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
 Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Magnus Damm <magnus.damm@...il.com>, Maxime Ripard <mripard@...nel.org>,
 Simona Vetter <simona@...ll.ch>, Thomas Zimmermann <tzimmermann@...e.de>,
 linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2] drm/rcar-du: dsi: Handle both DRM_MODE_FLAG_N.SYNC and
 !DRM_MODE_FLAG_P.SYNC

Hi again,

On 04/12/2025 14:54, Tomi Valkeinen wrote:
> Hi,
> 
> On 02/12/2025 20:11, Marek Vasut wrote:
>> Since commit 94fe479fae96 ("drm/rcar-du: dsi: Clean up handling of DRM mode flags")
>> the driver does not set TXVMVPRMSET0R_VSPOL_LOW and TXVMVPRMSET0R_HSPOL_LOW
>> for modes which set neither DRM_MODE_FLAG_[PN].SYNC. The previous behavior
>> was to assume that neither flag means DRM_MODE_FLAG_N.SYNC . Restore the
>> previous behavior for maximum compatibility.
>>
>> The change of behavior is visible below, consider Vertical mode->flags
>> for simplicity sake, although the same applies to Horizontal ones:
>>
>> Before 94fe479fae96 ("drm/rcar-du: dsi: Clean up handling of DRM mode flags") :
>>
>> - DRM_MODE_FLAG_PVSYNC => vprmset0r |= 0
>> - DRM_MODE_FLAG_NVSYNC => vprmset0r |= TXVMVPRMSET0R_VSPOL_LOW
>> - Neither DRM_MODE_FLAG_[PN]VSYNC => vprmset0r |= TXVMVPRMSET0R_VSPOL_LOW
>>
>> After 94fe479fae96 ("drm/rcar-du: dsi: Clean up handling of DRM mode flags") :
>>
>> - DRM_MODE_FLAG_PVSYNC => vprmset0r |= 0
>> - DRM_MODE_FLAG_NVSYNC => vprmset0r |= TXVMVPRMSET0R_VSPOL_LOW
>> - Neither DRM_MODE_FLAG_[PN]VSYNC => vprmset0r |= 0 <---------- This broke
>>
>> The "Neither" case behavior is different, because DRM_MODE_FLAG_N[HV]SYNC is
>> really not equivalent !DRM_MODE_FLAG_P[HV]SYNC .
>>
>> Fixes: 94fe479fae96 ("drm/rcar-du: dsi: Clean up handling of DRM mode flags")
>> Signed-off-by: Marek Vasut <marek.vasut+renesas@...lbox.org>
> 
> Thanks, looks good to me. Pushing to drm-misc-next.

Actually, drm-misc-next-fixes looks the correct one for this.

 Tomi

> 
>  Tomi
> 
>> ---
>> Cc: David Airlie <airlied@...il.com>
>> Cc: Geert Uytterhoeven <geert+renesas@...der.be>
>> Cc: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
>> Cc: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
>> Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
>> Cc: Magnus Damm <magnus.damm@...il.com>
>> Cc: Maxime Ripard <mripard@...nel.org>
>> Cc: Simona Vetter <simona@...ll.ch>
>> Cc: Thomas Zimmermann <tzimmermann@...e.de>
>> Cc: Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>
>> Cc: dri-devel@...ts.freedesktop.org
>> Cc: linux-kernel@...r.kernel.org
>> Cc: linux-renesas-soc@...r.kernel.org
>> ---
>> V2: - Update commit message
>>     - Use only !P[HV]SYNC
>> ---
>>  drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c b/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
>> index 9413b76d0bfce..4ef2e3c129ed7 100644
>> --- a/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
>> +++ b/drivers/gpu/drm/renesas/rcar-du/rcar_mipi_dsi.c
>> @@ -492,9 +492,9 @@ static void rcar_mipi_dsi_set_display_timing(struct rcar_mipi_dsi *dsi,
>>  
>>  	/* Configuration for Video Parameters, input is always RGB888 */
>>  	vprmset0r = TXVMVPRMSET0R_BPP_24;
>> -	if (mode->flags & DRM_MODE_FLAG_NVSYNC)
>> +	if (!(mode->flags & DRM_MODE_FLAG_PVSYNC))
>>  		vprmset0r |= TXVMVPRMSET0R_VSPOL_LOW;
>> -	if (mode->flags & DRM_MODE_FLAG_NHSYNC)
>> +	if (!(mode->flags & DRM_MODE_FLAG_PHSYNC))
>>  		vprmset0r |= TXVMVPRMSET0R_HSPOL_LOW;
>>  
>>  	vprmset1r = TXVMVPRMSET1R_VACTIVE(mode->vdisplay)
>