On 07/02/13 03:57, Daniel Drake wrote: > On Mon, Jul 1, 2013 at 3:48 PM, Sebastian Hesselbarth > <sebastian.hesselbarth at gmail.com> wrote: >> I prefer not to try to find the best clock (source) at all. Let the >> user pass the clock name by e.g. platform_data (or DT) and just try to >> get the requested pixclk or a integer multiple of it. You will never be >> able to find the best clock for all use cases. >> >> Just figure out, if integer division is sufficient to get requested >> pixclk and clk_set_rate otherwise. This may be useful for current mode >> running at 148.5MHz (1080p50) and new mode at 74.25MHz (1080i50, 720p). > > I am not opposed to this approach, it is nice and simple, but as > Russell points out we do additionally need to distinguish between > clocks that are "ours" to play with, vs those that are shared with > other devices. It would be a bad idea to try call clk_set_rate() on > the AXI bus clock, for example, changing the clock for a whole bunch > of other devices. This is what the is_dedicated flag is about. However > such a flag could be easily added to the DT/platform data definition > that you propose.
Daniel, now I got the idea of .is_dedicated. At least for Dove, we could still implement AXI bus clock as fixed-rate clock, so you cannot mess with it. I am almost sure, it will hang Dove when you change it, as there are some devices depending on it (and the correct rate of it). Moreover, LCDCLK is dedicated to CRTC0/1 so AXICLK is the only clock not dedicated to LCD controllers. But I am fine with .is_dedicated - I just think we should not try to find the best clock source but leave that decision to the user (=developer, DTS author; not userspace user). Sebastian
