On Mon, Apr 15, 2019 at 12:22:22PM +0300, Tero Kristo wrote: > On 15/04/2019 11:56, Keerthy wrote: > > > > > >On 15/04/19 7:43 AM, keerthy wrote: > >> > >> > >>On 4/15/2019 6:35 AM, Tom Rini wrote: > >>>On Mon, Apr 15, 2019 at 06:19:31AM +0530, keerthy wrote: > >>>> > >>>> > >>>>On 4/13/2019 6:32 PM, Tom Rini wrote: > >>>>>On Fri, Apr 12, 2019 at 12:08:14PM +0530, Keerthy wrote: > >>>>> > >>>>>>The series adds the support for hardware leveling. This needs the > >>>>>>kernel to be patched with hardware leveling support and the > >>>>>>kernel support is already in linux-next: > >>>>>> > >>>>>>https://patchwork.kernel.org/project/linux-omap/list/?series=100273 > >>>>>> > >>>>>>Match recommended values from EMIF Tools app note: > >>>>>>http://www.ti.com/lit/an/sprac70/sprac70.pdf > >>>>> > >>>>>What happens if you boot an old kernel with this series applied? > >>>>>I'm a > >>>>>bit worried about applying something that breaks existing kernels, > >>>>>thanks! > >>>> > >>>>Hi Tom, > >>>> > >>>>Deep Sleep 0 feature will fail as the corresponding hardware leveling > >>>>patches will not be present. > >>> > >>>So to be clear, some new functionality will not work, but there is no > >>>functional regression? > >> > >>Okay i got your concern. Deep sleep 0 is currently working with software > >>leveling that will stop working with this patch series(hardware > >>leveling) applied on older kernels. EMIF tools application note > >>recommends hardware leveling over what existed previously. > >> > >>Hence i posted this series. Older kernels with this patch series Deep > >>sleep 0 feature will regress. > > > >Tom, > > > >We need hardware leveling as per EMIF document. So older kernels at best > >can backport the patches here: > > > >https://patchwork.kernel.org/patch/10882123/ > >https://patchwork.kernel.org/patch/10882127/ > > > >I do not see any other way to enable hardware leveling. > > > >Tero/Dave, > > > >Any concerns? > > Well, if we are to enable the feature, I can't see how we can avoid conflict > with older kernels. However, most of the time I would say people upgrade > their kernel before upgrading u-boot so this should be fine. If we are > really worried, we could maybe add the support to kernel first, wait some > time and merge the support to u-boot after that.
I assume that as the patches are working their way through -next now, we're also talking about older vendor tree kernels being where this did work? -- Tom
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