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

[Javier Martinez Canillas]

Hello Marek,

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.

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America