On 27/01/16 16:00, Mark Brown wrote: > On Wed, Jan 27, 2016 at 03:18:20PM +0000, Damien Horsley wrote: >> On 27/01/16 14:57, Mark Brown wrote: >>> On Tue, Jan 26, 2016 at 02:34:26PM +0000, Damien Horsley wrote: > >>>> + - clock-names : Includes the following entries: >>>> + "audio_pll" The audio PLL >>>> + "i2s_mclk" The i2s reference clock >>>> + Also connected to i2s_out_0_mclk output >>>> + "dac_mclk" Dac reference clock. Connected to i2s_dac_clk output > >>> Why are these (especially the dac_mclk and i2s_mclk) properties of the >>> card and not of the drivers for the respective devices? > >> Due to the shared nature of these clocks. Individual components cannot >> be responsible for controlling these as this could break configurations >> for other components that are sharing the clocks. Only the card driver >> has visibility of all of the components and their requirements. > > You're talking about the code that decides what rates to set the clock > at, not where the properties are placed in the DT. > >> i2s_mclk and dac_mclk can be used by both the i2s in and i2s out paths >> on some boards > > Multiple devices can reference the same clock. > audio_pll is referenced exclusively by the card device i2s_mclk and dac_mclk can also be referenced by other devices. The i2s out controller references i2s_mclk, and codec devices can reference i2s_mclk/dac_mclk dependent on their system clock requirements without a reference to i2s_mclk and dac_mclk in the card driver, it would not be possible to control the divisors and gates for these clocks in the following cases: Simplistic codecs that do not have drivers Codec drivers that do not call clk_set_rate and clk_enable/clk_disable _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
