On 01/13/2012 04:05 PM, Simon Glass wrote: > On Fri, Jan 13, 2012 at 2:04 PM, Yen Lin <ye...@nvidia.com> wrote: >> On Fri, 2012-01-13 at 11:34 -0800, Simon Glass wrote: >>> On Tue, Jan 10, 2012 at 10:30 AM, Stephen Warren <swar...@nvidia.com> wrote: >>>> On 12/26/2011 12:33 PM, Simon Glass wrote: ... >>> But there a few questions here. Firstly it seems that it saves some >>> memory speed info to scratch2 but never restores it. Then it restores >>> CPU speed from scratch3 but I can't see where it saves it. Does Yen >>> have any comments on that? Apparently it works because we have been >>> using it, but... If it is saving things that are never restored I >>> could dump that and reduce the code size. >>> >> >> U-boot code saves sdram parameters to scratch2, scratch4, and scratch 24 >> registers, so when system resumes, bootrom can restore sdram parameters >> from these registers. >> >> The scratch3 register content was saved by kernel before suspend, and is >> used by the warmboot code to restore PLLX settings. > > Thanks for the info. > > On resume I do not see it using scratch2, 4 or 24 within U-Boot. Are > those used in the kernel?
The Tegra boot ROM (which contains the power-on code for the AVP) is what interprets these, according to Yen above. One question for Yen: Why doesn't the boot ROM read the SDRAM parameters from the BCT like it does during a cold boot? Perhaps there's some interaction with clock settings, so the boot ROM needs to know the clock/voltage/... state the kernel was in when suspending, rather than just using the "usual" cold boot settings? > I should add something to document this so the kernel people can match > up when that side of it goes up stream. -- nvpublic _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
