Hello Anand, On 10/22/2015 07:03 AM, Anand Moon wrote: > Hi Javier, > > On 22 October 2015 at 08:22, Javier Martinez Canillas > <javier@xxxxxxxxxxxxxxx> wrote: >> Hello Krzysztof, >> >> On 10/22/2015 03:43 AM, Krzysztof Kozlowski wrote: >>> On 22.10.2015 10:20, Javier Martinez Canillas wrote:> Hello Krzysztof, >>>> >>>> Thanks for your feedback. >>>> >>>> On 10/22/2015 02:36 AM, Krzysztof Kozlowski wrote: >>>>> On 22.10.2015 00:15, Javier Martinez Canillas wrote: >>>>>> The pwrseq_emmc driver does a eMMC card reset before a system reboot to >>>>>> allow broken or limited ROM boot-loaders (that don't have an eMMC reset >>>>>> logic) to be able to read the second stage from the eMMC. >>>>>> >>>>>> But this has to be called before a system reboot handler and while most >>>>>> of them use the priority 128, there are other restart handlers (such as >>>>>> the syscon-reboot one) that use a higher priority. So, use the highest >>>>>> priority to make sure that the eMMC hw is reset before a system reboot. >>>>>> >>>>>> Signed-off-by: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx> >>>>>> Tested-by: Markus Reichl <m.reichl@xxxxxxxxxxxxx> >>>>>> Tested-by: Anand Moon <linux.amoon@xxxxxxxxx> >>>>>> Reviewed-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx> >>>>>> >>>>>> --- >>>>>> Hello, >>>>>> >>>>>> This patch was needed since a recent series from Alim [0] added >>>>>> syscon reboot and poweroff support to Exynos SoCs and removed >>>>>> the reset handler in the Exynos Power Management Unit (PMU) code. >>>>>> >>>>>> But the PMU and syscon-reboot restart handler have a different >>>>>> priority so [0] breaks restart when eMMC is used on these boards. >>>>>> >>>>>> [0]: http://www.spinics.net/lists/arm-kernel/msg454396.html >>>>>> >>>>>> So this patch must be merged before [0] to avoid regressions. >>>>>> >>>>>> Best regards, >>>>>> Javier >>>>>> >>>>>> drivers/mmc/core/pwrseq_emmc.c | 6 +++--- >>>>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>>>> >>>>>> diff --git a/drivers/mmc/core/pwrseq_emmc.c b/drivers/mmc/core/pwrseq_emmc.c >>>>>> index 137c97fb7aa8..ad4f94ec7e8d 100644 >>>>>> --- a/drivers/mmc/core/pwrseq_emmc.c >>>>>> +++ b/drivers/mmc/core/pwrseq_emmc.c >>>>>> @@ -84,11 +84,11 @@ struct mmc_pwrseq *mmc_pwrseq_emmc_alloc(struct mmc_host *host, >>>>>> >>>>>> /* >>>>>> * register reset handler to ensure emmc reset also from >>>>>> - * emergency_reboot(), priority 129 schedules it just before >>>>>> - * system reboot >>>>>> + * emergency_reboot(), priority 255 is the highest priority >>>>>> + * so it will be executed before any system reboot handler. >>>>>> */ >>>>>> pwrseq->reset_nb.notifier_call = mmc_pwrseq_emmc_reset_nb; >>>>>> - pwrseq->reset_nb.priority = 129; >>>>>> + pwrseq->reset_nb.priority = 255; >>>>> >>>>> I see the problem which you are trying to solve but this may be tricker >>>>> then just kicking the number. Some of restart handlers are registered >>>>> with priority 192. I found few of such, like: at91_restart_nb, >>>>> zynq_slcr_restart_nb, rmobile_reset_nb (maybe more, I did not grep too >>>>> much). >>>>> >>>> >>>> Yes, the syscon-reboot restart handler also uses a priority 192 and that >>>> is why reboot with eMMC broke with Alim's patches since the PMU restart >>>> handler priority is 128. >>>> >>>>> I guess they chose the "192" priority on purpose. >>>>> >>>> >>>> I tried to understand what's the policy w.r.t priority numbering for >>>> restart handlers but only found this in the register_restart_handler >>>> kernel-doc [0]: >>>> >>>> /** >>>> * register_restart_handler - Register function to be called to reset >>>> * the system >>>> * @nb: Info about handler function to be called >>>> * @nb->priority: Handler priority. Handlers should follow the >>>> * following guidelines for setting priorities. >>>> * 0: Restart handler of last resort, >>>> * with limited restart capabilities >>>> * 128: Default restart handler; use if no other >>>> * restart handler is expected to be available, >>>> * and/or if restart functionality is >>>> * sufficient to restart the entire system >>>> * 255: Highest priority restart handler, will >>>> * preempt all other restart handlers >>>> >>>> So, reading that is not clear to me if only the values 0, 128 and 255 >>>> should be used or any value from 0-255. >>>> >>>> What's clear to me is that restart handlers to reset a specific hw block >>>> should be called before the restart handler that resets the whole system. >>>> >>>> The 192 seems to be used because there are other default restart handlers >>>> that are using a prio of 128. See for example the commit that changed the >>>> syscon-reboot prio from 128 to 192: >>>> >>>> b81180b3fd48 power: reset: adjust priority of simple syscon reboot driver >>> >>> But were are here not talking about syscon handler but the others. Now >>> you will be ahead of them. >>> >> >> Yes, I know that. My point was that the platforms were either not using the >> mmc-pwrseq-emmc or their system restart handler already had a lower priority >> but that is not true for at least rk3288-veyron as you said. >> >>>> >>>> So probably the 192 value was chosen because is in the middle of 128 and >>>> 255 but it seems to me a rather arbitrary value and I would prefer it to >>>> be documented in some place. >>>> >>>>> Effectively, now the emmc handler will be executed before their >>>>> handlers... is it an issue? Maybe some testing on these platforms is >>>>> necessary? >>>>> >>>> >>>> I don't think is an issue, the reason why I chose 255 is that it is >>>> a documented value in the kernel-doc and since is the highest prio, >>>> it makes sure the eMMC will be reset before any system restart handler. >>>> >>>> Also, the pwrseq_emmc driver is only used in platforms whose SoC ROM >>>> can either leave the eMMC in an unknown state so the kernel needs to >>>> hw reset the eMMC or does not have a reset logic so it can only read >>>> from an eMMC if is in a known state (i.e: after a reset from kernel). >>> >>> I think at least one platform may be affected because it used >>> mmc-pwrseq-emmc and gpio-restart. >>> >>> Look at rk3288-veyron.dtsi. >>> >>> Both of restart handlers had the priority of 129 which means that the >>> order of execution depends on probing sequence. Now you will make the >>> sequence strict - first mmc then gpio. >>> >> >> The behavior is going to change indeed in that board but no due probe >> order but because the gpio-restart handler dev node has priority = <200> >> which overrides the default 129 in the gpio-restart driver. >> >> So before $SUBJECT the eMMC restart handler was not executed but now it >> will be after this change. >> >>> You seems convinced that this is not a problem... I don't know. I would >>> prefer test this on affected platforms before risking to break them. >>> It's annoying if fix for one SoC breaks another. >>> >> >> Agreed. >> >>>> >>>> Since the current mmc_pwrseq_emmc_reset_nb notifier priority is 129, >>>> eMMC reset will not work if one of the platforms you mentioned needs >>>> this since the system restart handler with prio 192 will be executed >>>> before the eMMC one, leaving the eMMC in an unknown state on reboot. >>> >>> And now you will "fix this" by making eMMC working correctly. So let's >>> make it straight: >>> 1. Previously the eMMC could be left on these platforms in an unknown >>> state (because emmc handler was not executed). >>> 2. No one complained! Which could mean that in fact this was working fine... >>> 3. Now you will change it. >>> 4. Maybe someone will complain? >>> >>> Just test it (or get an ack/tested tag). That's all what is needed. >>> >> >> Yes, I never meant that the patch should be merged without testing... >> >>> >>>> And $SUBJECT should not cause any regressions for the platforms that >>>> are currently using the pwrseq_emmc, since the restart handler was >>>> already being called before the system restart handler so bumping >>>> the priority should not cause any effect. >>> >>> I found at least one platform where the sequence *might* change. There >>> could be more of them. >>> >> >> Agreed, I missed that rk3288-veyron is using a restart handler with higher >> priority and could be other boards too as you said. >> >> Let's see what is Marek's opinion since he added the pwrseq_emmc support >> and also what Ulf thinks about always doing a eMMC reset before reboot. >> >> I can't think how doing a eMMC card reset before reboot could affect a >> board but you are right that we don't know without testing. >> >>> Best regards, >>> Krzysztof >>> >> > > Well I have tested with > > pwrseq->reset_nb.priority = 192; > I'm not sure why you are testing that case to be honest. > But it did not resolve the issue of reboot. > That's expected since you are using the same priority for both the mmc-pwrseq-emmc and syscon-reboot restart handlers so it will only work if the eMMC restart handler is registered before the syscon one and I don't if that's the case. The eMMC restart handler priority should be higher than the one used by syscon-reboot (or any system restart handler) to work. > will early rest of emmc will that not affect the sync of data before reboot. > Is this a question? It shouldn't since the restart handlers are the last things that are executed before a system is rebooted. > -Anand Moon > Best regards, -- Javier Martinez Canillas Open Source Group Samsung Research America -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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