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Date: Thu, 19 Jan 2017 11:56:02 -0300
From: Javier Martinez Canillas <javier@....samsung.com>
To: Marek Szyprowski <m.szyprowski@...sung.com>,
linux-kernel@...r.kernel.org
Cc: Inki Dae <inki.dae@...sung.com>,
Andi Shyti <andi.shyti@...sung.com>,
Shuah Khan <shuahkh@....samsung.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Kukjin Kim <kgene@...nel.org>,
linux-samsung-soc@...r.kernel.org,
Sylwester Nawrocki <s.nawrocki@...sung.com>,
linux-media@...r.kernel.org, Krzysztof Kozlowski <krzk@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 2/2] [media] exynos-gsc: Fix imprecise external abort due
disabled power domain
Hello Marek,
Thanks a lot for your feedback.
On 01/19/2017 11:17 AM, Marek Szyprowski wrote:
> Hi Javier,
>
> On 2017-01-18 01:30, Javier Martinez Canillas wrote:
>> Commit 15f90ab57acc ("[media] exynos-gsc: Make driver functional when
>> CONFIG_PM is unset") removed the implicit dependency that the driver
>> had with CONFIG_PM, since it relied on the config option to be enabled.
>>
>> In order to work with !CONFIG_PM, the GSC reset logic that happens in
>> the runtime resume callback had to be executed on the probe function.
>>
>> The problem is that if CONFIG_PM is enabled, the power domain for the
>> GSC could be disabled and so an attempt to write to the GSC_SW_RESET
>> register leads to an unhandled fault / imprecise external abort error:
>
> Driver core ensures that driver's probe() is called with respective power
> domain turned on, so this is not the right reason for the proposed change.
>
Ok, I misunderstood the relationship between runtime PM and the power domains
then. I thought the power domains were only powered on when the runtime PM
framework resumed an associated device (i.e: pm_runtime_get_sync() is called).
But even if this isn't the case, shouldn't the reset in probe only be needed
if CONFIG_PM isn't enabled? (IOW, $SUBJECT but with another commit message).
>> [ 10.178825] Unhandled fault: imprecise external abort (0x1406) at 0x00000000
>> [ 10.186982] pgd = ed728000
>> [ 10.190847] [00000000] *pgd=00000000
>> [ 10.195553] Internal error: : 1406 [#1] PREEMPT SMP ARM
>> [ 10.229761] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
>> [ 10.237134] task: ed49e400 task.stack: ed724000
>> [ 10.242934] PC is at gsc_wait_reset+0x5c/0x6c [exynos_gsc]
>> [ 10.249710] LR is at gsc_probe+0x300/0x33c [exynos_gsc]
>> [ 10.256139] pc : [<bf2429e0>] lr : [<bf240734>] psr: 60070013
>> [ 10.256139] sp : ed725d30 ip : 00000000 fp : 00000001
>> [ 10.271492] r10: eea74800 r9 : ecd6a2c0 r8 : ed7d8854
>> [ 10.277912] r7 : ed7d8c08 r6 : ed7d8810 r5 : ffff8ecd r4 : c0c03900
>> [ 10.285664] r3 : 00000000 r2 : 00000001 r1 : ed7d8b98 r0 : ed7d8810
>>
>> So only do a GSC reset if CONFIG_PM is disabled, since if is enabled the
>> runtime PM resume callback will be called by the VIDIOC_STREAMON ioctl,
>> making the reset in probe unneeded.
>>
>> Fixes: 15f90ab57acc ("[media] exynos-gsc: Make driver functional when CONFIG_PM is unset")
>> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
>
> Frankly, I don't get why this change is needed.
>
Yes, it seems $SUBJECT is just papering over the real issue. There's
something really wrong with the Exynos power domains, I see that PDs
can't be disabled by the genpd framework, exynos_pd_power_off() fail:
# dmesg | grep power-domain
[ 4.893318] Power domain power-domain@...44020 disable failed
[ 4.893342] Power domain power-domain@...44120 disable failed
[ 4.893711] Power domain power-domain@...44000 disable failed
[ 12.690052] Power domain power-domain@...44000 disable failed
[ 12.703963] Power domain power-domain@...44000 disable failed
So PD are kept on even when unused / attached devices are suspended.
Only the mfc_pd (power-domain@...44060) is correctly turned off.
# cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
domain status slaves
/device runtime status
----------------------------------------------------------------------
power-domain@...440C0 on
/devices/platform/soc/14450000.mixer active
/devices/platform/soc/14530000.hdmi active
power-domain@...44120 on
power-domain@...44060 off-0
/devices/platform/soc/11000000.codec suspended
power-domain@...44020 on
power-domain@...44000 on
/devices/platform/soc/13e00000.video-scaler suspended
/devices/platform/soc/13e10000.video-scaler suspended
Also when removing the exynos_gsc driver, I get the same error:
# rmmod s5p_mfc
[ 106.405972] s5p-mfc 11000000.codec: Removing 11000000.codec
# rmmod exynos_gsc
[ 227.008559] Unhandled fault: imprecise external abort (0x1c06) at 0x00048e14
[ 227.015116] pgd = ed5dc000
[ 227.017213] [00048e14] *pgd=b17c6835
[ 227.020889] Internal error: : 1c06 [#1] PREEMPT SMP ARM
...
[ 227.241585] [<bf2429bc>] (gsc_wait_reset [exynos_gsc]) from [<bf24009c>] (gsc_runtime_resume+0x9c/0xec [exynos_gsc])
[ 227.252331] [<bf24009c>] (gsc_runtime_resume [exynos_gsc]) from [<c042e488>] (genpd_runtime_resume+0x120/0x1d4)
[ 227.262294] [<c042e488>] (genpd_runtime_resume) from [<c04241c0>] (__rpm_callback+0xc8/0x218)
# cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
domain status slaves
/device runtime status
----------------------------------------------------------------------
power-domain@...440C0 on
/devices/platform/soc/14450000.mixer active
/devices/platform/soc/14530000.hdmi active
power-domain@...44120 on
power-domain@...44060 off-0
power-domain@...44020 on
power-domain@...44000 on
/devices/platform/soc/13e00000.video-scaler suspended
/devices/platform/soc/13e10000.video-scaler resuming
This seems to be caused by some needed clocks to access the power domains
to be gated, since I don't get these erros when passing clk_ignore_unused
as parameter in the kernel command line.
Best regards,
--
Javier Martinez Canillas
Open Source Group
Samsung Research America
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