From fd70c7755bf0172ddd33b558aef69c322de3b5cf Mon Sep 17 00:00:00 2001
From: Tomi Valkeinen <tomi.valkeinen@ti.com>
Date: Tue, 24 Sep 2019 16:17:02 +0300
Subject: drm/bridge: tc358767: fix max_tu_symbol value
Git-commit: fd70c7755bf0172ddd33b558aef69c322de3b5cf
Patch-mainline: v5.4-rc3
References: bsc#1152472
max_tu_symbol was programmed to TU_SIZE_RECOMMENDED - 1, which is not
what the spec says. The spec says:
roundup ((input active video bandwidth in bytes/output active video
bandwidth in bytes) * tu_size)
It is not quite clear what the above means, but calculating
max_tu_symbol = (input Bps / output Bps) * tu_size seems to work and
fixes the issues seen.
This fixes artifacts in some videomodes (e.g. 1024x768@60 on 2-lanes &
1.62Gbps was pretty bad for me).
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Tested-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190924131702.9988-1-tomi.valkeinen@ti.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/bridge/tc358767.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
index cebc8e620820..8a8d605021f0 100644
--- a/drivers/gpu/drm/bridge/tc358767.c
+++ b/drivers/gpu/drm/bridge/tc358767.c
@@ -728,6 +728,8 @@ static int tc_set_video_mode(struct tc_data *tc,
int lower_margin = mode->vsync_start - mode->vdisplay;
int vsync_len = mode->vsync_end - mode->vsync_start;
u32 dp0_syncval;
+ u32 bits_per_pixel = 24;
+ u32 in_bw, out_bw;
/*
* Recommended maximum number of symbols transferred in a transfer unit:
@@ -735,7 +737,10 @@ static int tc_set_video_mode(struct tc_data *tc,
* (output active video bandwidth in bytes))
* Must be less than tu_size.
*/
- max_tu_symbol = TU_SIZE_RECOMMENDED - 1;
+
+ in_bw = mode->clock * bits_per_pixel / 8;
+ out_bw = tc->link.base.num_lanes * tc->link.base.rate;
+ max_tu_symbol = DIV_ROUND_UP(in_bw * TU_SIZE_RECOMMENDED, out_bw);
dev_dbg(tc->dev, "set mode %dx%d\n",
mode->hdisplay, mode->vdisplay);
--
2.28.0