Hi Tomi, On Fri, Mar 15, 2019 at 03:30:11PM +0200, Tomi Valkeinen wrote: > On 15/03/2019 14:28, Peter Ujfalusi wrote: > > On 15/03/2019 14.07, Tomi Valkeinen wrote: > >>> If the pclk-sample is not defined in DT, it will default to 0 which > >>> selects SAMPLE_NEGEDGE (== DRIVE_POSEDGE), right? > >>> > >>> But all the boards where I can find schematics with tfp410 have their > >>> EDGE/HTPLG pin pulled up and according to the documentation when EDGE=1 > >>> then tfp410 will sample on the rising edge. > >>> > >>> imho the pclk_sample should be initialized to 1 to avoid regression for > >>> most of the boards using tfp410. > >> > >> Define "regression" =). If the omapdrm driver was always using > >> DRIVE_POSEDGE, this driver should also be using DRIVE_POSEDGE, no? If it > >> does the same as the old driver, it can't be a regression. This is, of > >> course, only considering omapdrm based boards. > >> > >> That said, it sounds odd that this would be wrong in the old driver, but > >> then again, it might well be, as code related to these sync signals has > >> changed sooo many times, and the related DSS registers are somewhat > >> confusing. > > > > On the boards data skew is enabled as well with maximum delay selected > > with DK1=DK2=DK3=1, so sampling of data is delayed by 3 * 350 ps, so > > about 1 ns, not much, but might be enough for the signal to transition > > on the bus so even if the HW drivers on POSEDGE and tfp410 samples on > > POSEDGE (+1ns delay from the edge) we don't see corruption? > > Ok. I don't think anyone has looked at it that closely. So, the syncs > could well be wrong. Still, not a regression if it's the same way as it was. > > If the fixed default works fine (or better) than the wrong ones, I think > that can be the default. But I'd be careful about changing what the > default is, if we've had it the old way for a long time.
I don't object changing the default (given proper testing), but that should be done on top of this series then. -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
