Messages in this thread | | | Date | Wed, 08 May 2019 18:38:39 -0700 | From | Sodagudi Prasad <> | Subject | Re: PSCI version 1.1 and SYSTEM_RESET2 |
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On 2019-05-02 02:05, Sudeep Holla wrote: > On Wed, May 01, 2019 at 11:43:00AM -0700, Sodagudi Prasad wrote: >> On 2019-05-01 02:49, Sudeep Holla wrote: >> > On Tue, Apr 30, 2019 at 05:07:31PM -0700, Sodagudi Prasad wrote: >> > > On 2019-04-30 14:44, Sodagudi Prasad wrote: > > [...] > >> > > >> > > It would nice if there is a config option to reboot the device >> > > either in >> > > warm or cold in the case of kernel panic. >> > >> > I presume you prefer to do warm boot in case of panic to get a dump of >> > the memory to inspect ? If so, is kexec/kdump not the mechanism to >> > achieve that ? >> >> Hi Sudeep, >> >> Thanks for your response and sharing details about your patch. >> >> > If so, is kexec/kdump not the mechanism to achieve that? >> > >> Qualcomm is having vendor specific solution to capture ram contents >> and for >> offline analysis. >> > > Ah OK. > >> > >> > I am just trying to understand the use case. Xilinx asked for the same >> > but never got to understand their use case. >> >> Here is the background - >> Usually, power off drivers are overriding arm_pm_restart and >> pm_power_off >> callbacks and registering with reboot notifier with some priority for >> the >> reboot operations. Here is the Qualcomm poweroff driver for >> reference. >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/power/reset/msm-poweroff.c >> >> Before vendor chip set specific power off driver is probed, >> arm_pm_restart >> functions pointer holds the psci_sys_reset function. Once vendor power >> off >> driver is probed, vendor drivers can override the arm_pm_restart >> function >> pointer. >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/firmware/psci.c#n562 >> >> Once vendor driver is probed, drivers can take care of devices warm or >> hard >> reset configuration part properly. But there is a window from >> start_kernel() to vendor specific driver probed, devices are getting >> cold >> resets even if kernel crashed. This is due to arm_pm_restart points >> to >> psci_sys_reset function by default. Is this problem clear now? >> > > Too specific use case IMO and I am not sure if we need a generic > solution > to deal with this. Anyways, I don't see any check in arch/psci specific > code for what you want, just ensure reboot_mode is set appropriately. > Post a patch and see what people have to say.
Hi Sudeep,
Yes. With your system_reset2 command support addition, just configuring the reboot_mode is good enough.
-Thanks, Prasad
> >> Qualcomm downstream kernel has a lot of use cases with respect device >> reset >> sequence and the downstream driver is much different from upstream >> drivers. >> I think, the above-mentioned problem is common for all the chipset >> vendors >> and it is not specific Qualcomm use cases. I have one downstream >> solution >> to this problem but thought to bring up this problem to the upstream >> community for a common solution, so that all the vendors can use it. >> > > May be or may be not, post the patch and let's see. > >> I have modified below flow to avoid cold restart in the case of early >> kernel >> panic. >> panic() --> emergency_restart() --> machine_emergency_restart() --> >> machine_restart(NULL); >> >> -Thanks, Prasad >> >> > >> > -- >> > Regards, >> > Sudeep >> >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora >> Forum, >> Linux Foundation Collaborative Project
-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, Linux Foundation Collaborative Project
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