On 15/03/2019 15.30, 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.
True. > 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. The HW default in I2C mode is the EDGE=1 so SAMPLE_POSEDGE and it looks to me that the same default was implemented via hw control on the boards I can access the schematics. If it was the other way in the past, then it is safer to not change the default in the driver, but probably put a comment somewhere that the HW default is the opposite? In any case if the i2c control is implemented we will read and/or configure the tfp410 anyways. - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
