phy: freescale: fsl-samsung-hdmi: return closest rate instead LUT

Commit Message

Dominique Martinet March 10, 2025, 1:21 a.m. UTC

From: Makoto Sato <[e-mail]>

If the requested rate is not an exact match of the integer divider
phy_clk_round_rate() would return the look up table value,
but phy_clk_set_rate() can still use the integer divider if it results
in a frequency that is closer than the look up table.

In particular, not returning the actually used value here made the hdmi
bridge driver reject a frequency that has an integer divider rate
within 0.5% of the target:
for 83.5mHz, the integer divider generates 83.2mHz (-0.36%), but the
next LUT value (82.5mHz) is 1.2% off which incorrectly rejects modes
requiring this frequency.

This commit updates phy_clk_round_rate() to use the same logic as the
set operation.

Signed-off-by: Makoto Sato <[e-mail]>
Signed-off-by: Dominique Martinet <[e-mail]>
---
We're finally using this rewrite in our (outdated) tree and noticed the
"best" mode missing on one of our picky displays.
It all looks good with this fix, thanks again!
---
 drivers/phy/freescale/phy-fsl-samsung-hdmi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)


---
base-commit: 80e54e84911a923c40d7bee33a34c1b4be148d7a
change-id: 20250310-8ulp_hdmi-f8deac08611e

Best regards,

Patch

diff --git a/drivers/phy/freescale/phy-fsl-samsung-hdmi.c b/drivers/phy/freescale/phy-fsl-samsung-hdmi.c
index e4c0a82d16d9ef0f64ebf9e505b8620423cdc416..91c4d27a31f48fc49f1e8417d7089f5519b8a0a2 100644
--- a/drivers/phy/freescale/phy-fsl-samsung-hdmi.c
+++ b/drivers/phy/freescale/phy-fsl-samsung-hdmi.c
@@ -557,8 +557,9 @@  static long phy_clk_round_rate(struct clk_hw *hw,
 	if (int_div_clk == rate)
 		return int_div_clk;
 
-	/* If neither rate is an exact match, use the value from the LUT */
-	return fract_div_phy->pixclk;
+	/* If neither rate is an exact match, use the closest value */
+	return fsl_samsung_hdmi_phy_get_closest_rate(rate, int_div_clk,
+						     fract_div_phy->pixclk);
 }
 
 static int phy_use_fract_div(struct fsl_samsung_hdmi_phy *phy, const struct phy_config *fract_div_phy)