phy: rockchip: samsung-hdptx: Pre-compute HDMI PLL config for 461.10125 MHz output

Attempting to make use of a 1080p@120Hz display mode with 10 bpc RGB on
my Acer XV275K P3 monitor results in a blank image.  A similar behavior
has been reported on Philips 279M1RV.

The faulty modeline is created by drm_gtf_mode_complex() based on the
following EDID entry from the Standard Timings block:

  GTF:  1920x1080  119.999987 Hz  16:9    138.840 kHz    368.759000 MHz

It's worth noting the computed pixel clock ends up being slightly higher
at 368.881000 MHz.  Nevertheless, this seems to work consistently fine
with 8 bpc RGB.

After switching to 10 bpc, the TMDS character rate expected for the mode
increases to 461.101250 MHz, as per drm_hdmi_compute_mode_clock().

Since there is no entry for this rate in the ropll_tmds_cfg table, the
necessary HDMI PLL configuration parameters are calculated dynamically
by rk_hdptx_phy_clk_pll_calc().  However, the resulting output rate is
not quite a perfect match, i.e. 461.100000 MHz.  That proved to be the
actual root cause of the problem.

Add a new entry to the TMDS configuration table and provide the
necessary frequency division coefficients for the PHY PLL to generate
the expected 461.101250 MHz output.

Fixes: 9d0ec51d7c22 ("phy: rockchip: samsung-hdptx: Add high color depth management")
Tested-by: Derek Foreman <derek.foreman@collabora.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://patch.msgid.link/20251221-phy-hdptx-pll-fix-v2-1-ae4abf7f75a1@collabora.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
index 29de2f7bdae8a31958e31b0a64281532fd76e64d..cafa618d70fdcad83ba43dcf3847906c4f4781f2 100644 (file)
--- a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
+++ b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
@@ -414,6 +414,8 @@ struct rk_hdptx_phy {
 static const struct ropll_config ropll_tmds_cfg[] = {
        { 594000000ULL, 124, 124, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 62, 1, 16, 5, 0,
          1, 1, 0, 0x20, 0x0c, 1, 0x0e, 0, 0, },
+       { 461101250ULL, 97, 97, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1, 71, 1, 53, 2, 6,
+         35, 1, 0, 0x20, 0x0c, 1, 0x0e, 0, 0, },
        { 371250000ULL, 155, 155, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 62, 1, 16, 5, 0,
          1, 1, 0, 0x20, 0x0c, 1, 0x0e, 0, 0, },
        { 297000000ULL, 124, 124, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 62, 1, 16, 5, 0,