Hi Richard, Santosh, On Thu, 16 Sep 2010, Shilimkar, Santosh wrote:
> > -----Original Message----- > > From: [email protected] [mailto:linux-omap- > > [email protected]] On Behalf Of Woodruff, Richard > > Sent: Thursday, September 16, 2010 11:36 AM > > To: Paul Walmsley; Hunter, Jon > > Cc: linux-omap; [email protected]; [email protected] > > Subject: RE: [PATCH] omap3: Prevent SDRC deadlock when L3 is changing > > frequency > > > > > > > From: [email protected] [mailto:linux-omap- > > > [email protected]] On Behalf Of Paul Walmsley > > > Sent: Wednesday, September 15, 2010 2:15 PM > > > > > > This patch fixes this problem by ensuring the branch prediction logic > > is > > > > disabled while changing the L3 clock frequency. The branch prediction > > logic > > > > is disabled by clearing the Z-bit in the ARM AUX CTRL register. > > > > Small correction, Z bit is in CR register. AUX CTRL figures in with the > > ASA feature. > > > > > Really nice changelog. I wish every patch had a description this good. > > > Patch looks really good, too. Queued for 2.6.37. > > > > It is system specific if this change is required. It is probably safer to > > have it than not. > > > > If the AUX CTRL register has the ASA bit/feature active to allow > > speculative accesses to propagate past the L2 boundary the Z bit should be > > cleared as in the patch. > > > > However, if ASA bit is not activated then Z bit clearing should not be > > necessary as speculation will be squashed if there is no L2 hit (so no DDR > > request will be generated). > > > > It is not recommended to enable ASA bit as it is known to cause some > > issues on EMU/HS devices. It was also projected as loosing more than it > > gained across some benchmarks. > > > > Early boot loaders used to set the ASA. It was removed long back. Some > > kernels kept the value and opened up the lockup window. I don't recall > > the linux-omap open kernel having the issue. Some vendor ones did over > > time. > > > The code seems to be correct but just the description has typo. The code > is using control register. I just corrected the description and white > space issue. Here is updated patch. > > Paul, > You can use this version if you like Thanks for the fixes, will update the patch.. - Paul -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
