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drm/bridge: tc358768: fix TCLK_TRAILCNT computation

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[ Upstream commit ee18698e212b1659dd0850d7e2ae0f22e16ed3d3 ]

Correct computation of TCLK_TRAILCNT register.

The driver does not implement non-continuous clock mode, so the actual
value doesn't make a practical difference yet. However this change also
ensures that the value does not write to reserved registers bits in case
of under/overflow.

This register must be set to a value that ensures that

TCLK-TRAIL > 60ns
 and
TEOT <= (105 ns + 12 x UI)

with the actual value of TCLK-TRAIL being

(TCLK_TRAILCNT + (1 to 2)) xHSByteClkCycle +
 (2 + (1 to 2)) * HSBYTECLKCycle - (PHY output delay)

with PHY output delay being about

(2 to 3) x MIPIBitClk cycle in the BitClk conversion.

Fixes: ff1ca6397b ("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/20230427142934.55435-2-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-3-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-4-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-5-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-2-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-3-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-4-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-5-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-2-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-3-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-4-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-5-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-2-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-3-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-4-francesco@dolcini.it
Link: https://patchwork.freedesktop.org/patch/msgid/20230427142934.55435-5-francesco@dolcini.it
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Francesco Dolcini 2023-04-27 16:29:30 +02:00 committed by Greg Kroah-Hartman
parent 33abcfbb17
commit 6b9450723b
1 changed files with 5 additions and 3 deletions
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8
drivers/gpu/drm/bridge/tc358768.c
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@ -10,6 +10,7 @@
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/media-bus-format.h>
#include <linux/minmax.h>
#include <linux/module.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>
@ -633,6 +634,7 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
struct tc358768_priv *priv = bridge_to_tc358768(bridge);
struct mipi_dsi_device *dsi_dev = priv->output.dev;
u32 val, val2, lptxcnt, hact, data_type;
s32 raw_val;
const struct drm_display_mode *mode;
u32 dsibclk_nsk, dsiclk_nsk, ui_nsk, phy_delay_nsk;
u32 dsiclk, dsibclk;
@ -733,9 +735,9 @@ static void tc358768_bridge_pre_enable(struct drm_bridge *bridge)
dev_dbg(priv->dev, "TCLK_HEADERCNT: 0x%x\n", val);
tc358768_write(priv, TC358768_TCLK_HEADERCNT, val);
/* TCLK_TRAIL > 60ns + 3*UI */
val = 60 + tc358768_to_ns(3 * ui_nsk);
val = tc358768_ns_to_cnt(val, dsibclk_nsk) - 5;
/* TCLK_TRAIL > 60ns AND TEOT <= 105 ns + 12*UI */
raw_val = tc358768_ns_to_cnt(60 + tc358768_to_ns(2 * ui_nsk), dsibclk_nsk) - 5;
val = clamp(raw_val, 0, 127);
dev_dbg(priv->dev, "TCLK_TRAILCNT: 0x%x\n", val);
tc358768_write(priv, TC358768_TCLK_TRAILCNT, val);