[PATCH v6 4/4] drm/rockchip: dw_hdmi: discard modes with unachievable pixelclocks

[Sascha Hauer]

The Rockchip PLL drivers are currently table based and support only
the most common pixelclocks. Discard all modes we cannot achieve
at all. Normally the desired pixelclocks have an exact match in the
PLL driver, nevertheless allow for a 0.1% error just in case.

Tested-by: Nicolas Frattaroli <frattaroli.nicolas at gmail.com>
Tested-by: Michael Riesch <michael.riesch at wolfvision.net>
Tested-by: Dan Johansen <strit at manjaro.org>
Link: https://lore.kernel.org/r/20230118132213.2911418-4-s.hauer@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---

Notes:
    Changes since v3:
    - only check for rate when clk != NULL
    
    Changes since v2:
    - new patch

 drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
index feba6b9becd6c..293dcf0f05931 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -260,6 +260,13 @@ dw_hdmi_rockchip_mode_valid(struct dw_hdmi *dw_hdmi, void *data,
 	bool exact_match = hdmi->plat_data->phy_force_vendor;
 	int i;
 
+	if (hdmi->ref_clk) {
+		int rpclk = clk_round_rate(hdmi->ref_clk, pclk);
+
+		if (abs(rpclk - pclk) > pclk / 1000)
+			return MODE_NOCLOCK;
+	}
+
 	for (i = 0; mpll_cfg[i].mpixelclock != (~0UL); i++) {
 		/*
 		 * For vendor specific phys force an exact match of the pixelclock
-- 
2.30.2