Hi Richard, >From: linux-omap-ow...@vger.kernel.org [mailto:linux-omap- >ow...@vger.kernel.org] On Behalf Of Woodruff, Richard > >> From: linux-omap-ow...@vger.kernel.org [mailto:linux-omap- >> ow...@vger.kernel.org] On Behalf Of Paul Walmsley >> Sent: Tuesday, October 20, 2009 8:21 PM > >> > This patch removes the SDRC AC timings changes done during core dvfs. >> > Updating AC timing CTRL values for SDRC during DVFS is seen to be a >risk, >> > while the RFR CTRL value is safe to be updated. >> > >> > Signed-off-by: Rajendra Nayak <rna...@ti.com> >> >> just wanted to let you know, I haven't forgotten about this one. Am >trying >> to get an answer from others as to whether AC timing register changes are >> completely unsafe, in which case your patch is probably the best way to >> move forward; or whether we can make the changes when no initiators are >> touching SDRAM. > >It is not guaranteed safe to write actim registers on the fly to an active >part. It is safe to do RFR as it is buffered and sent out at a safe time.
I think that what Paul is suggesting is to change the ACTIM after ensuring that the DDR is in self-refresh. In that case it is perfectly valid; it is just tricky to ensure that all initiators are in mute before doing that. Regards, Benoit >A few years back before omap3 as part of omap2 lessons learned this issue >was highlighted but design was not able to change. Recently implementation >review at rtl provided the above points. > >I'm not aware of anyone seeing a crash but recommendation for safety is to >not. > >Regards, >Richard W. > >-- >To unsubscribe from this list: send the line "unsubscribe linux-omap" in >the body of a message to majord...@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html Texas Instruments France SA, 821 Avenue Jack Kilby, 06270 Villeneuve Loubet. 036 420 040 R.C.S Antibes. Capital de EUR 753.920 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
