From: Francesco Dolcini francesco.dolcini@toradex.com
[ Upstream commit f9cf811374f42fca31ac34aaf59ee2ae72b89879 ]
Correct computation of TCLK_ZEROCNT register.
This register must be set to a value that ensure that (TCLK-PREPARECNT + TCLK-ZERO) > 300ns
with the actual value of (TCLK-PREPARECNT + TCLK-ZERO) being
(1 to 2) + (TCLK_ZEROCNT + 1)) x HSByteClkCycle + (PHY output delay)
with PHY output delay being about
(2 to 3) 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/20230427142934.55435-5-frances... Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/bridge/tc358768.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c index dba1bf3912f1e..aff400c360662 100644 --- a/drivers/gpu/drm/bridge/tc358768.c +++ b/drivers/gpu/drm/bridge/tc358768.c @@ -742,10 +742,10 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
/* 38ns < TCLK_PREPARE < 95ns */ val = tc358768_ns_to_cnt(65, dsibclk_nsk) - 1; - /* TCLK_PREPARE > 300ns */ - val2 = tc358768_ns_to_cnt(300 + tc358768_to_ns(3 * ui_nsk), - dsibclk_nsk); - val |= (val2 - tc358768_to_ns(phy_delay_nsk - dsibclk_nsk)) << 8; + /* TCLK_PREPARE + TCLK_ZERO > 300ns */ + val2 = tc358768_ns_to_cnt(300 - tc358768_to_ns(2 * ui_nsk), + dsibclk_nsk) - 2; + val |= val2 << 8; dev_dbg(priv->dev, "TCLK_HEADERCNT: 0x%x\n", val); tc358768_write(priv, TC358768_TCLK_HEADERCNT, val);