On 03/21/2013 12:46 PM, Martin Fuzzey wrote: > On 21/03/13 17:11, Timur Tabi wrote: >> On Thu, Mar 21, 2013 at 3:39 AM, Martin Fuzzey <mfuzzey@xxxxxxxxxxx> wrote: >> >>> With this patch and that DT example the frequency of clock 162 will be _set_ >>> to 20MHz >> Does that mean that it ignores the ' clocks' parameter? > No, in this case the clocks parameter must contain the phandle of a clock > whose rate is configurable. > >> If clock-frequency is omitted the binding is still correct (hence the >> optional) but the frequency of clock 162 would not be modified. >> >> In the documentation I wrote "If both a clock and clock-frequency are >> provided the clock's rate will be set. " maybe this is not clear enough? >> It's not clear what it will be set *to*. > It will be set to the frequency specified by the clock-frquency attribute. > > Would > "If both a clock and clock-frequency are provided clock must support > the set_rate operation and its frequency will be set to the value specified > by clock-frequency" be better? Yes, that's much better. > > > The possible configurations and their use cases are: > > 1) only 'clocks' specified > clock points to a clock specified in the DT which already has an > appropriate frequency and is > configured by some other means external to the sgtl5000 driver > (bootloader, board setup code, or just a fixed rate clock) > > 2) only 'clock-frequency' specified > The chip is assumed to be clocked by a signal having the given > frequency, which may even be generated by a clock unknown to linux. > This could actually be represented as a special case of 1) by defining a > fixed-rate clock in the DT. > > 3) Both 'clocks' and 'clock-frequency' specified > The chip is assumed to be clocked by a rate programmable clock defined > in the clock tree. > clk_set_rate() will be called for this clock to set its rate to that > specified by clock-frequency This should all be in the binding document. > Cases 1 and 2 exist in the current code, this patch adds support for case 3. > > Prior to commit 81e8e4926167ab32593bbb915b45a42024ca1020 "ASoC: fsl: add > sgtl5000 clock support for imx-sgtl5000" > only case 2 was supported > This explains why 2 is not implemented as a special case of 1) > plain 'clock-frequency' was supported before the driver learnt how to > get a clock from the DT And this should be in the patch description. -- Timur Tabi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
