[U-Boot] [PATCH 0/6] board: ti: am43xx: Enable hardware leveling

[Tom Rini <trini@konsulko.com>]

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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