From: Francesco Dolcini francesco.dolcini@toradex.com
[ Upstream commit bac7842cd179572e8e0fc2d7b5254e40c6e9e057 ]
Correct computation of THS_TRAILCNT register.
This register must be set to a value that ensure that THS_TRAIL > 60 ns + 4 x UI and THS_TRAIL > 8 x UI and THS_TRAIL < TEOT with TEOT = 105 ns + (12 x UI)
with the actual value of THS_TRAIL being
(1 + THS_TRAILCNT) x ByteClk cycle + ((1 to 2) + 2) xHSBYTECLK cycle + - (PHY output delay)
with PHY output delay being about
(8 + (5 to 6)) x MIPIBitClk cycle in the BitClk conversion.
Fixes: ff1ca6397b1d ("drm/bridge: Add tc358768 driver") Signed-off-by: Francesco Dolcini francesco.dolcini@toradex.com Reviewed-by: Robert Foss rfoss@kernel.org Signed-off-by: Robert Foss rfoss@kernel.org Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-9-frances... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/bridge/tc358768.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c index d8209433d5f43..966a25cb0b108 100644 --- a/drivers/gpu/drm/bridge/tc358768.c +++ b/drivers/gpu/drm/bridge/tc358768.c @@ -780,9 +780,10 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge) dev_dbg(priv->dev, "TCLK_POSTCNT: 0x%x\n", val); tc358768_write(priv, TC358768_TCLK_POSTCNT, val);
- /* 60ns + 4*UI < THS_PREPARE < 105ns + 12*UI */ - val = tc358768_ns_to_cnt(60 + tc358768_to_ns(15 * ui_nsk), - dsibclk_nsk) - 5; + /* max(60ns + 4*UI, 8*UI) < THS_TRAILCNT < 105ns + 12*UI */ + raw_val = tc358768_ns_to_cnt(60 + tc358768_to_ns(18 * ui_nsk), + dsibclk_nsk) - 4; + val = clamp(raw_val, 0, 15); dev_dbg(priv->dev, "THS_TRAILCNT: 0x%x\n", val); tc358768_write(priv, TC358768_THS_TRAILCNT, val);