Re: [PATCH 2/2] [media] exynos-gsc: Fix imprecise external abort due disabled power domain

From: Marek Szyprowski
Date: Fri Jan 20 2017 - 03:37:59 EST


Hi Javier,

On 2017-01-19 18:51, Javier Martinez Canillas wrote:
On 01/19/2017 11:56 AM, Javier Martinez Canillas wrote:
On 01/19/2017 11:17 AM, Marek Szyprowski wrote:
[snip]

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@100440C0 on
/devices/platform/soc/14450000.mixer active
/devices/platform/soc/14530000.hdmi active
power-domain@10044120 on
power-domain@10044060 off-0
power-domain@10044020 on
power-domain@10044000 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.

I found the issue. The problem was that Exynos5422 needs not only the
CLK_ACLK_ 300_GSCL but also CLK_ACLK432_SCALER to be ungated in order
to access the GSCL IP block.

The Exynos5422 manual shows in Figure 7-14 that ACLK_432_SCLAER is needed
for the internal buses.

Exynos5420 only needs CLK_ACLK_ 300_GSCL to be ungated.

With following hack, the issue goes away for the gsc_pd in the Odroid XU4:

diff --git a/drivers/clk/samsung/clk-exynos5420.c b/drivers/clk/samsung/clk-exynos5420.c
index 8c8b495cbf0d..9876ec28b94c 100644
--- a/drivers/clk/samsung/clk-exynos5420.c
+++ b/drivers/clk/samsung/clk-exynos5420.c
@@ -586,7 +586,7 @@ static const struct samsung_gate_clock exynos5800_gate_clks[] __initconst = {
GATE(CLK_ACLK550_CAM, "aclk550_cam", "mout_user_aclk550_cam",
GATE_BUS_TOP, 24, 0, 0),
GATE(CLK_ACLK432_SCALER, "aclk432_scaler", "mout_user_aclk432_scaler",
- GATE_BUS_TOP, 27, 0, 0),
+ GATE_BUS_TOP, 27, CLK_IS_CRITICAL, 0),
};

# cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
domain status slaves
/device runtime status
----------------------------------------------------------------------
power-domain@100440C0 on
/devices/platform/soc/14450000.mixer active
/devices/platform/soc/14530000.hdmi active
power-domain@10044120 on
power-domain@10044060 off-0
/devices/platform/soc/11000000.codec suspended
power-domain@10044020 on
power-domain@10044000 off-0
/devices/platform/soc/13e00000.video-scaler suspended
/devices/platform/soc/13e10000.video-scaler suspended

# rmmod s5p_mfc
[ 82.885227] s5p-mfc 11000000.codec: Removing 11000000.codec
# rmmod exynos_gsc

# cat /sys/kernel/debug/pm_genpd/pm_genpd_summary
domain status slaves
/device runtime status
----------------------------------------------------------------------
power-domain@100440C0 on
/devices/platform/soc/14450000.mixer active
/devices/platform/soc/14530000.hdmi active
power-domain@10044120 on
power-domain@10044060 off-0
power-domain@10044020 on
power-domain@10044000 off-0
I'll post a proper patch for the exynos5800.dtsi, to override the
clocks in the gsc_pd device node.

I also see that the two power domains that fail to be disabled msc_pd
(power-domain@10044120) and isp_pd (power-domain@10044020) don't have
clocks defined in the exynos54xx.dtsi. I'll add clocks for those too.

Please send this patch instead of adding more clocks to the power domains.
This way we will avoid adding more dependencies to userspace (DT ABI).
Likely those clocks are also needed to access any device in that power
domains.

Later, once the runtime PM for clocks get merged, a patch for exynos542x
clocks driver can be made to replace IS_CRITICAL with proper runtime
handling.

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland