Messages in this thread | | | Subject | Re: [PATCH] leds: leds-pca963x: workaround group blink scaling issue | From | Jacek Anaszewski <> | Date | Mon, 17 Oct 2016 09:58:26 +0200 |
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On 10/15/2016 02:00 PM, Matt Ranostay wrote: > On Fri, Oct 14, 2016 at 7:20 AM, Tony Lindgren <tony@atomide.com> wrote: >> * Jacek Anaszewski <j.anaszewski@samsung.com> [161013 23:37]: >>> On 10/13/2016 04:20 PM, Matt Ranostay wrote: >>>> On Thu, Oct 13, 2016 at 4:05 PM, Jacek Anaszewski >>>> <j.anaszewski@samsung.com> wrote: >>>>> Why DT property? Is it somehow dependent on the board configuration? >>>>> How this period-scale value is calculated? Is it inferred empirically? >>>>> >>>> >>>> We empirically discovered and verified this with an logic analyzer on >>>> multiple batches of this part. >>>> Reason for the DT entry is we aren't 100% sure that it is always going >>>> to be the same with different board revs. >>>> >>>> Could be that parts clock acts differently with supply voltage. This >>>> has been calculated by setting it an expected value, and measuring the >>>> actual result with the logic analyzer. >>> >>> I'd like to have DT maintainer's ack for this. >>> >>> Cc Rob and Mark. >> >> How about do this based on the compatible property instead? If there >> are multiple manufacturers for this part and only a certain >> parts have this issue we should have multiple compatible properties. >> > > I could only find that NXP as the manufacturer of that part. It is > possible since the clock is internal to the chipset that the vdd of > 2.5V is doing something undefined. > >> Then if it turns out all of them need this scaling there's no need >> to update the binding. > > Understandable.
Since at present we can't guarantee that all produced devices are affected, then we should strive to avoid breaking any existing users of the possible non-affected devices.
In view of that the addition of a new "compatible" proposed by Tony seems most reasonable.
Still, DT maintainer's opinion is required.
-- Best regards, Jacek Anaszewski
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