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drm/bridge: imx8mp-hdmi-tx: allow 0.5% margin with selected clock

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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

Tested-by: Adam Ford <aford173@gmail.com> #imx8mp-beacon
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20240907-hdmi-tolerance-v2-1-b9d7abd89f5c@codewreck.org
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240907-hdmi-tolerance-v2-1-b9d7abd89f5c@codewreck.org
This commit is contained in:
Dominique Martinet 2024-09-07 14:54:33 +09:00 committed by Neil Armstrong
parent 8fdd9cb4f8
commit 0d4b950e03
1 changed files with 9 additions and 2 deletions
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11
drivers/gpu/drm/bridge/imx/imx8mp-hdmi-tx.c
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@ -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 +31,14 @@ 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);
/* imx8mp's pixel clock generator (fsl-samsung-hdmi) cannot generate
* all possible frequencies, so allow some tolerance to support more
* modes.
* Allow 0.5% difference allowed in various standards (VESA, CEA861)
* 0.5% = 5/1000 tolerance (mode->clock is 1/1000)
*/
if (abs(round_rate - mode->clock * 1000) > mode->clock * 5)
return MODE_CLOCK_RANGE;
/* We don't support double-clocked and Interlaced modes */