15.01.2014 13:27, Jyri Sarha kirjoitti: > On 12/31/2013 03:25 PM, Mark Brown wrote: >> On Fri, Dec 20, 2013 at 12:39:38PM +0200, Jyri Sarha wrote: >>> support. The only supported sample format is SNDRV_PCM_FORMAT_S32_LE. >>> The 8 least significant bits are ignored. >> >> Where does this constraint come from? >> > > From driver/gpu/drm/i2c/tda998x_drv.c. The driver configures CTS_N > register statically to a value that works only with 4 byte samples. > According to my tests it is possible to support 3 and 2 byte samples too > by changing the CTS_N register value, but I am not sure if the > configuration can be changed on the fly. My data sheet of the nxp chip > is very vague about the register definitions, but I suppose the register > configures some clock divider on the chip. HDMI supports only upto 24bit > audio and the data sheet states that any extraneous least significant > bits are ignored. That sounds strange, CTS/N values only depend on audio sample rate and TMDS/video clock, not on the audio format or the size of samples (HDMI spec sec 7.2 - Audio Sample Clock Capture and Regeneration). Sure there isn't anything more going on (like the used HDMI sink being more tolerant to wrong CTS/N with 4-byte samples, or more likely something else I can't immediately think of)? BTW, radeon driver has some code that calculates static CTS/N values since the hw autogeneration is not reliable there: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/radeon/r600_hdmi.c Not that it directly helps now, but just for the record... -- Anssi Hannula -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
