linux-kernel - Re: [RFC PATCH 2/2] ARM: EXYNOS: Make sure that the Exynos5420 MDMA0 clock is enabled during suspend

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Date:	Fri, 27 Mar 2015 15:38:12 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier.martinez@...labora.co.uk>
Cc:	Kukjin Kim <kgene@...nel.org>,
	Doug Anderson <dianders@...omium.org>,
	Olof Johansson <olof@...om.net>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Abhilash Kesavan <kesavan.abhilash@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Tyler Baker <tyler.baker@...aro.org>,
	Steve Capper <steve.capper@...aro.org>,
	Amit Kucheria <amit.kucheria@...aro.org>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] ARM: EXYNOS: Make sure that the Exynos5420 MDMA0
 clock is enabled during suspend

2015-03-27 15:21 GMT+01:00 Javier Martinez Canillas
<javier.martinez@...labora.co.uk>:
> Commit ae43b3289186 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power
> Management support v12") added pm support for the pl330 dma driver but
> it makes the clock for the Exynos5420 MDMA0 DMA controller to be gated
> during suspend and this clock needs to remain enabled in order to make
> the system resume from a system suspend state.
>
> To make sure that the clock is enabled during suspend, enable it prior
> to entering a suspend state and disable it once the system has resumed.
>
> Thanks to Abhilash Kesavan for figuring out that this was the issue.
>
> Fixes: ae43b32 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power Management support v12")
> Signed-off-by: Javier Martinez Canillas <javier.martinez@...labora.co.uk>

Hmmm... isn't a real problem elsewhere - like some clock hierarchy is
wrong or incomplete? This rather looks like workaround for the
problem.

> ---
>  arch/arm/mach-exynos/suspend.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/arch/arm/mach-exynos/suspend.c b/arch/arm/mach-exynos/suspend.c
> index 1521eaf99265..6dbc0a6d1bb5 100644
> --- a/arch/arm/mach-exynos/suspend.c
> +++ b/arch/arm/mach-exynos/suspend.c
> @@ -16,6 +16,7 @@
>  #include <linux/init.h>
>  #include <linux/suspend.h>
>  #include <linux/syscore_ops.h>
> +#include <linux/clk.h>
>  #include <linux/cpu_pm.h>
>  #include <linux/io.h>
>  #include <linux/irq.h>
> @@ -79,6 +80,7 @@ static const struct exynos_pm_data *pm_data;
>
>  static int exynos5420_cpu_state;
>  static unsigned int exynos_pmu_spare3;
> +static struct clk *clk;
>
>  /*
>   * GIC wake-up support
> @@ -374,6 +376,16 @@ static void exynos5420_pm_prepare(void)
>  {
>         unsigned int tmp;
>
> +       /*
> +        * Exynos5420 requires the MDMA0 controller clock to be
> +        * ungated on suspend in order to be resumed correctly.
> +        */
> +       clk = clk_get(NULL, "mdma0");
> +       if (IS_ERR(clk))
> +               pr_warn("Failed to get mdma0 clk (%ld)\n", PTR_ERR(clk));
> +       else
> +               clk_prepare_enable(clk);
> +
>         /* Set wake-up mask registers */
>         exynos_pm_set_wakeup_mask();
>
> @@ -516,6 +528,9 @@ static void exynos5420_pm_resume(void)
>  {
>         unsigned long tmp;
>
> +       if (!IS_ERR_OR_NULL(clk))
> +               clk_disable_unprepare(clk);
> +

Missing clk_put()

Best regards,
Krzysztof
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