From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keerthy Date: Mon, 15 Apr 2019 17:40:27 +0530 Subject: [U-Boot] [PATCH 0/6] board: ti: am43xx: Enable hardware leveling In-Reply-To: <20190415112820.GU4664@bill-the-cat> References: <20190412063820.25924-1-j-keerthy@ti.com> <20190413130247.GJ4664@bill-the-cat> <5274f3fd-057e-04aa-5423-96ab6b304a28@ti.com> <20190415010520.GT4664@bill-the-cat> <9cc9a21f-4864-5867-4469-318e42a9600c@ti.com> <57c9af5e-43c9-aec7-d5d7-72a923b338b2@ti.com> <20190415112820.GU4664@bill-the-cat> Message-ID: <769ff12b-b671-031d-2dc9-7a50a23e7e7a@ti.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de 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?