Hi Rusell,
在 2015/3/31 18:35, Russell King - ARM Linux 写道:
On Tue, Mar 31, 2015 at 02:55:53AM -0400, Yang Kuankuan wrote:
Hi Russell,
I'm okay with this change, and also I am preparing that collect N/CTS setting to an array, like this :
struct n_cts { unsigned int cts; unsigned int n; }; struct tmds_n_cts { unsigned long tmds; /* 1 entry each for 32KHz, 44.1KHz, and 48KHz */ struct n_cts n_cts[3]; }; static const struct tmds_n_cts n_cts_table[] = { { 25175000, {{ 28125, 4576}, { 31250, 7007}, { 25175, 6144} } }, }I think this is something which should be a common helper rather than being specific to the driver. I believe these are the standard values for coherent audio/video clocks which can be found in the HDMI specifications. Such a helper should document that it is only for use when the audio and video clocks are coherent.
Yep, it will be logical to add the n/cts calcu to a common helper. And actually the HDMI specifications have give the Revommended N and Expected CTS values for several standard TMDS clock rates(25.2/1.001 ...).
(The HDMI spec gives alternative N values for use with auto-CTS value generation for non-coherent clocks.)
I'd also prefer the lookup to use the same units as the drm_display_mode video clock specification, which is kHz, so we can eventually kill the needless *1000 in dw_hdmi.
One of the issues with using a common helper is that the common helper would include the 1.001 clocks, which are allegedly unsupported by the FSL iMX6 implementation, and, if proven that they don't work, we would need some way to disable audio for those devices.
Okay, but rockchip platform can handle the 1.001 clocks, so maybe we can call some valid function from dw_hdmi-imx & dw_hdmi-rockchip to mark the effective clock that platform support ?
But I am confused by the "hdmi->ratio", this variable was modify to 100 in bind funciton, then nowhere would change it again. In this case "hdmi->ratio" seems an unused variable, can we remove it ?
I guess the FSL sources should be checked to find out what the intended use for that was, and we then need to decide whether to keep it (and implement it) or remove it.
Need FSL ack...
Best regards. Yakir Yang