Hi! Dne torek, 18. junij 2019 ob 01:55:58 CEST je Douglas Anderson napisal(a): > Let's add some better support for HDMI audio to dw_hdmi. > Specifically: > > 1. For 44.1 kHz audio the old code made the assumption that an N of > 6272 was right most of the time. That wasn't true and the new table > should give better 44.1 kHz audio for many more rates. > > 2. The new table has values from the HDMI spec for 297 MHz and 594 > MHz. > > 3. There is now code to try to come up with a more idea N/CTS for > clock rates that aren't in the table. This code is a bit slow because > it iterates over every possible value of N and picks the best one, but > it should make a good fallback. > > 4. The new code allows for platforms that know they make a clock rate > slightly differently to pick different N/CTS values. For instance on > rk3288 we can make 25,176,471 Hz instead of 25,174,825.1748... Hz > (25.2 MHz / 1.001). A future patch to the rk3288 platform code could > enable support for this clock rate and specify the N/CTS that would be > ideal. > > NOTE: the oddest part of this patch comes about because computing the > ideal N/CTS means knowing the _exact_ clock rate, not a rounded > version of it. The drm framework makes this harder by rounding rates > to kHz, but even if it didn't there might be cases where the ideal > rate could only be calculated if we knew the real (non-integral) rate. > This means that in cases where we know (or believe) that the true rate > is something other than the rate we are told by drm. > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> Which bus is used for audio transfer on your device? If it is I2S, which is commonly used, then please be aware of this patch: https://lists.freedesktop.org/archives/dri-devel/2019-June/221539.html It avoids exact N/CTS calculation by enabling auto detection. It is well tested on multiple SoCs from Allwinner, Amlogic and Rockchip. Best regards, Jernej _______________________________________________ Linux-rockchip mailing list Linux-rockchip@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/linux-rockchip
