[alsa-devel] [PATCH 2/4] drm/i915: implement set_ncts callback

[Takashi Iwai]

On Thu, 06 Aug 2015 08:52:55 +0200,
libin.yang at intel.com wrote:
> 
> From: Libin Yang <libin.yang at intel.com>
> 
> Display audio may not work at some frequencies
> with the HW provided N/CTS.
> 
> This patch sets the proper N value for the
> given audio sample rate at the impacted frequencies.
> At other frequencies, it will use the N/CTS value
> which HW provides.
> 
> Signed-off-by: Libin Yang <libin.yang at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h    |  2 +
>  drivers/gpu/drm/i915/intel_audio.c | 93 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 95 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 3a77678..0b1cd72 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7010,6 +7010,8 @@ enum skl_disp_power_wells {
>  					_HSW_AUD_MISC_CTRL_A, \
>  					_HSW_AUD_MISC_CTRL_B)
>  
> +#define HSW_AUD_PIPE_CONN_SEL_CTRL  0x650ac
> +
>  #define _HSW_AUD_DIP_ELD_CTRL_ST_A	0x650b4
>  #define _HSW_AUD_DIP_ELD_CTRL_ST_B	0x651b4
>  #define HSW_AUD_DIP_ELD_CTRL(pipe) _PIPE(pipe, \
> diff --git a/drivers/gpu/drm/i915/intel_audio.c b/drivers/gpu/drm/i915/intel_audio.c
> index dc32cf4..f1148cd 100644
> --- a/drivers/gpu/drm/i915/intel_audio.c
> +++ b/drivers/gpu/drm/i915/intel_audio.c
> @@ -68,6 +68,28 @@ static const struct {
>  	{ 148500, AUD_CONFIG_PIXEL_CLOCK_HDMI_148500 },
>  };
>  
> +static const struct {
> +	int sample_rate;
> +	int clock;
> +	int n;
> +	int cts;
> +} aud_ncts[] = {
> +	{ 44100, DIV_ROUND_UP(297000 * 1000, 1001), 4459, 234375 },
> +	{ 44100, 297000, 4704, 247500 },

As these two clock values are referred repeatedly in other places,
it'd be better to define constants.


Takashi