From fd70c7755bf0172ddd33b558aef69c322de3b5cf Mon Sep 17 00:00:00 2001 From: Tomi Valkeinen Date: Tue, 24 Sep 2019 16:17:02 +0300 Subject: drm/bridge: tc358767: fix max_tu_symbol value 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 Tested-by: Jyri Sarha Signed-off-by: Andrzej Hajda Link: https://patchwork.freedesktop.org/patch/msgid/20190924131702.9988-1-tomi.valkeinen@ti.com --- drivers/gpu/drm/bridge/tc358767.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'drivers') 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); -- cgit