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!