Messages in this thread | | | Date | Thu, 20 Mar 2014 10:37:53 +0800 | From | Bo Shen <> | Subject | Re: [PATCH 7/8] ASoC: atmel: document clock properties of the wm8904 driver |
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Hi Mark,
On 03/19/2014 06:28 PM, Mark Brown wrote: > On Wed, Mar 19, 2014 at 01:57:23PM +0800, Bo Shen wrote: >> On 03/17/2014 07:55 PM, Mark Brown wrote: > >>> If this is a clock for the CODEC it should be documented as part of the >>> binding for the CODEC and connected to the CODEC in the device tree >>> rather than being part of a machine driver binding. > >> This is a optional clock for CODEC which depends on hardware design. There >> are 3 options for this clock, wm8904 as an example. >> 1. Using internal FLL, so won't use this clock. >> 2. Using external oscillator, no need to retrieve this clock. >> 3. Using SoC provide this clock (we use this case). > >> After considering these 3 options, if we put this into CODEC driver to do >> it, I think it will be more complicate to do logic judgement. Do you think >> so? > > There shouldn't be any meaningful complexity from the above cases - > cases 2 and 3 are the same and if the clock isn't used at all then it > can be omitted. If the FLL is clocked from MCLK then the CODEC driver > should be able to work out how to configure it easily, the device isn't > like a digital hub CODEC with lots of clocking options.
For this, in my mind, I think we need add following parameters in DT. 1. sysclk_src_from_fll --> we need do nothing. 2. sysclk_src_from_mclk 2.1 use_external_xtal --> we need clock_frequency 2.2 !use_external_xtal --> we need retrieve clock and clock_frequency.
So, the dt may looks like: for case 1: wm8904: wm8904@1a { reg = <0x1a>; sysclk_src_from_fll; }
for case 2.1: wm8904: wm8904@1a { reg = <0x1a>; sysclk_src_from_mclk; use_external_xtal; clock_frequency = 12000000; }
for case 2.2: wm8904: wm8904@1a { reg = <0x1a>; sysclk_src_from_mclk; clocks = <&pck0>; clock-names = "mclk"; clock_frequency = 32768; }
Does this acceptable? Or any other better suggestion for this?
Best Regards, Bo Shen
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