[PATCH v4 4/4] drm/rockchip: dw_hdmi: discard modes with unachievable pixelclocks

[Sascha Hauer <s.hauer@pengutronix.de>]

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@gmail.com>
Tested-by: Michael Riesch <michael.riesch@wolfvision.net>
Tested-by: Dan Johansen <strit@manjaro.org>
Link: https://lore.kernel.org/r/20230118132213.2911418-4-s.hauer@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
index feba6b9becd6c..725952811752b 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -256,10 +256,14 @@ dw_hdmi_rockchip_mode_valid(struct dw_hdmi *dw_hdmi, void *data,
 {
 	struct rockchip_hdmi *hdmi = data;
 	const struct dw_hdmi_mpll_config *mpll_cfg = rockchip_mpll_cfg;
-	int pclk = mode->clock * 1000;
+	int rpclk, pclk = mode->clock * 1000;
 	bool exact_match = hdmi->plat_data->phy_force_vendor;
 	int i;
 
+	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


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