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

[Tom Rini]

On Mon, Apr 15, 2019 at 05:40:27PM +0530, Keerthy wrote:
> 
> 
> On 15/04/19 4:58 PM, Tom Rini wrote:
> >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?
> >
> 
> older kernels will have to port the above patches else Deep Sleep 0 will
> fail with newer u-boot with hardware leveling enabled. I assume they would
> be using older u-boot as well?

Yes, it sounds like there's reasonable support matrices here, thanks!

-- 
Tom
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