On Thu, 2012-04-19 at 10:31 +0100, Russell King - ARM Linux wrote: > On Wed, Apr 18, 2012 at 01:43:46PM +0530, Archit Taneja wrote: > > On Wednesday 18 April 2012 01:36 PM, Tomi Valkeinen wrote: > >> Hi, > >> > >> On Mon, 2012-04-09 at 12:41 +0530, Archit Taneja wrote: > >>> This reverts commit 46f8c3c7e95c0d30d95911e7975ddc4f93b3e237. > >>> > >>> The commit above swapped the DSI1_PPID and DSI2_PPID register fields in > >>> CONTROL_DSIPHY to be in sync with the newer public OMAP TRMs(after version V). > >>> > >>> With this commit, contention errors were reported on DSI lanes some OMAP4 SDPs. > >>> After probing the DSI lanes on OMAP4 SDP, it was seen that setting bits in the > >>> DSI2_PPID field was pulling up voltage on DSI1 lanes, and DSI1_PPID field was > >>> pulling up voltage on DSI2 lanes. > >>> > >>> This proves that the current version of OMAP4 TRM is incorrect, swap the > >>> position of register fields according to the older TRM versions as they were > >>> correct. > >> > >> Are we sure the bits are the same for all OMAP4 versions? I'm just > >> wondering why the change was made to TRM... > > > > I've tried on OMAP4430 ES2.1 and OMAP4460 ES1.1. I can try on a couple > > more revisions. > > > > As far as why the change was made in the TRM, it's a bit hard to find > > the right people, or get response from them :), I'll give that a try > > again. > > > > If we do conclude that this revert patch is needed, it might probably be > > a candidate for the 3.2 and 3.3 stable kernels, just wanted to point > > that out. > > I was just going to ask about this, as I haven't noticed any improvement > in mainline kernels since I reported the original failure... It seems to be very difficult to find out why the TRM change was done, and what the HW actually does. But as the boards out there are clearly fixed by reverting the original patch, I think it's best if we just apply the revert. Archit, can you resend the patch with my ack, and cc stable@xxxxxxxxxxxxxxx (see Documentation/stable_kernel_rules.txt). Tomi
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