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

[Marek Szyprowski]

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