[PATCH] drm/bridge: imx8mp-hdmi-tx: allow 0.5% margin with selected clock
From: Dominique Martinet
Date: Wed Sep 04 2024 - 04:31:35 EST
This allows the hdmi driver to pick e.g. 64.8MHz instead of 65Mhz when we
cannot output the exact frequency, enabling the imx8mp HDMI output to
support more modes
Signed-off-by: Dominique Martinet <dominique.martinet@xxxxxxxxxxxxxxxxx>
---
This completes the patch series sent by Adam Ford here:
https://lkml.kernel.org/r/20240904023310.163371-1-aford173@xxxxxxxxx
and makes the cheap screens we recommend work with our imx8mp board
without further kludging.
drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c b/drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c
index 13bc570c5473..9431cd5e06c3 100644
--- a/drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c
+++ b/drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c
@@ -23,6 +23,7 @@ imx8mp_hdmi_mode_valid(struct dw_hdmi *dw_hdmi, void *data,
const struct drm_display_mode *mode)
{
struct imx8mp_hdmi *hdmi = (struct imx8mp_hdmi *)data;
+ long round_rate;
if (mode->clock < 13500)
return MODE_CLOCK_LOW;
@@ -30,8 +31,9 @@ imx8mp_hdmi_mode_valid(struct dw_hdmi *dw_hdmi, void *data,
if (mode->clock > 297000)
return MODE_CLOCK_HIGH;
- if (clk_round_rate(hdmi->pixclk, mode->clock * 1000) !=
- mode->clock * 1000)
+ round_rate = clk_round_rate(hdmi->pixclk, mode->clock * 1000);
+ /* accept 0.5% = 1/200 = 5/1000 tolerance */
+ if (abs(round_rate - mode->clock * 1000) > mode->clock * 5)
return MODE_CLOCK_RANGE;
/* We don't support double-clocked and Interlaced modes */
--
2.39.2