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

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Message-ID: <20251202181146.138365-1-marek.vasut+renesas@mailbox.org>
Date: Tue,  2 Dec 2025 19:11:06 +0100
From: Marek Vasut <marek.vasut+renesas@...lbox.org>
To: dri-devel@...ts.freedesktop.org
Cc: Marek Vasut <marek.vasut+renesas@...lbox.org>,
	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>,
	Tomi Valkeinen <tomi.valkeinen+renesas@...asonboard.com>,
	linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org
Subject: [PATCH v2] drm/rcar-du: dsi: Handle both DRM_MODE_FLAG_N.SYNC and !DRM_MODE_FLAG_P.SYNC

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>
---
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)
-- 
2.51.0