From mboxrd@z Thu Jan 1 00:00:00 1970 From: Santosh Shilimkar Subject: Re: [PATCH v2 09/18] ARM: OMAP4+: PM: Restore CPU power state to ON with clockdomain force wakeup method Date: Fri, 5 Apr 2013 17:28:22 +0530 Message-ID: <515EBC5E.6090705@ti.com> References: <1364205910-32392-1-git-send-email-santosh.shilimkar@ti.com> <1364205910-32392-10-git-send-email-santosh.shilimkar@ti.com> <87mwtftjvy.fsf@linaro.org> <515D8215.10705@ti.com> <87li8ynqf5.fsf@linaro.org> <515E9435.6050007@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <515E9435.6050007@ti.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Kevin Hilman Cc: nm@ti.com, tony@atomide.com, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: linux-omap@vger.kernel.org On Friday 05 April 2013 02:37 PM, Santosh Shilimkar wrote: > On Thursday 04 April 2013 11:12 PM, Kevin Hilman wrote: >> Santosh Shilimkar writes: >> >>> On Thursday 04 April 2013 02:24 AM, Kevin Hilman wrote: >>>> Santosh Shilimkar writes: >>>> >>>>> While waking up CPU from off state using clock domain force wakeup, restore >>>>> the CPU power state to ON state before putting CPU clock domain under >>>>> hardware control. Otherwise CPU wakeup might fail. The change is recommended >>>>> for all OMAP4+ devices though the PRCM weakness was observed on OMAP5 >>>>> devices first. >>>> >>>> Sounds reasonable, but can you describe the "weakness" a little more? >>>> >>>> IOW, what exactly happens if this is not done? It sounds like the CPU >>>> might immediately go back to retention, but how does that happen unless >>>> it does a WFI? >>>> >>> Its more of lock-up inside the hardware state machine and results >>> are UN-predictable. We have seen hard-locks most of the time where system >>> is just frozen. The hardware gets into wrong state machine if the power >>> domain state isn't restored. I will add this information to changelog. >>> >>>> Also, this sounds like a fix to me, and should probably be broken out >>>> accordingly. >>>> >>> Yeah. You mean a separate patch from the series, right ? This patch >>> actually can be independently added. >>> >>> In case you decide to apply it for the fixes branch, updated patch >>> at end of the email. >> >> Curious which branch you applied it to? It didn't apply cleanly to >> v3.9-rc5 (but did with fuzz). >> > Mostly applied on top of the Tony's pull request branches. > >> So I've now added it to my for_3.10/fixes/pm branch. >> > Thanks. I will pull that in to re-base other patches. > While pulling your 'for_3.10/fixes/pm' branch on top of Tony's pull request[1] sent to arm-soc already. In my tree, I had pulled Tony's couple of pull requests. Regards, Santosh [1] http://www.spinics.net/lists/arm-kernel/msg235788.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: santosh.shilimkar@ti.com (Santosh Shilimkar) Date: Fri, 5 Apr 2013 17:28:22 +0530 Subject: [PATCH v2 09/18] ARM: OMAP4+: PM: Restore CPU power state to ON with clockdomain force wakeup method In-Reply-To: <515E9435.6050007@ti.com> References: <1364205910-32392-1-git-send-email-santosh.shilimkar@ti.com> <1364205910-32392-10-git-send-email-santosh.shilimkar@ti.com> <87mwtftjvy.fsf@linaro.org> <515D8215.10705@ti.com> <87li8ynqf5.fsf@linaro.org> <515E9435.6050007@ti.com> Message-ID: <515EBC5E.6090705@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Friday 05 April 2013 02:37 PM, Santosh Shilimkar wrote: > On Thursday 04 April 2013 11:12 PM, Kevin Hilman wrote: >> Santosh Shilimkar writes: >> >>> On Thursday 04 April 2013 02:24 AM, Kevin Hilman wrote: >>>> Santosh Shilimkar writes: >>>> >>>>> While waking up CPU from off state using clock domain force wakeup, restore >>>>> the CPU power state to ON state before putting CPU clock domain under >>>>> hardware control. Otherwise CPU wakeup might fail. The change is recommended >>>>> for all OMAP4+ devices though the PRCM weakness was observed on OMAP5 >>>>> devices first. >>>> >>>> Sounds reasonable, but can you describe the "weakness" a little more? >>>> >>>> IOW, what exactly happens if this is not done? It sounds like the CPU >>>> might immediately go back to retention, but how does that happen unless >>>> it does a WFI? >>>> >>> Its more of lock-up inside the hardware state machine and results >>> are UN-predictable. We have seen hard-locks most of the time where system >>> is just frozen. The hardware gets into wrong state machine if the power >>> domain state isn't restored. I will add this information to changelog. >>> >>>> Also, this sounds like a fix to me, and should probably be broken out >>>> accordingly. >>>> >>> Yeah. You mean a separate patch from the series, right ? This patch >>> actually can be independently added. >>> >>> In case you decide to apply it for the fixes branch, updated patch >>> at end of the email. >> >> Curious which branch you applied it to? It didn't apply cleanly to >> v3.9-rc5 (but did with fuzz). >> > Mostly applied on top of the Tony's pull request branches. > >> So I've now added it to my for_3.10/fixes/pm branch. >> > Thanks. I will pull that in to re-base other patches. > While pulling your 'for_3.10/fixes/pm' branch on top of Tony's pull request[1] sent to arm-soc already. In my tree, I had pulled Tony's couple of pull requests. Regards, Santosh [1] http://www.spinics.net/lists/arm-kernel/msg235788.html