linux-kernel - Re: [PATCH] soc: tegra: pmc: restrict compilation of suspend-related support to ARM

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Date:	Wed, 10 Dec 2014 12:23:23 +0100
From:	Thierry Reding <treding@...dia.com>
To:	Paul Walmsley <paul@...an.com>
CC:	<linux-soc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-tegra@...r.kernel.org>, Kumar Gala <galak@...eaurora.org>,
	"Paul Walmsley" <pwalmsley@...dia.com>,
	Allen Martin <amartin@...dia.com>,
	"Stephen Warren" <swarren@...dia.com>,
	Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH] soc: tegra: pmc: restrict compilation of suspend-related
 support to ARM

On Tue, Dec 09, 2014 at 10:36:50PM +0000, Paul Walmsley wrote:
> 
> Tegra SoCs with 64-bit ARM support don't currently support deep CPU
> low-power states in mainline Linux.  When this support is added in the
> future, it will probably look rather different from the existing
> 32-bit ARM support, since the ARM64 maintainers' strong preference is
> to use PSCI to implement it.
> 
> So, for the time being, prevent the CPU suspend-related code and data
> in the Tegra PMC driver from compiling on ARM64.
> 
> Signed-off-by: Paul Walmsley <paul@...an.com>
> Signed-off-by: Paul Walmsley <pwalmsley@...dia.com>
> Cc: Thierry Reding <treding@...dia.com>
> Cc: Allen Martin <amartin@...dia.com>
> Cc: Stephen Warren <swarren@...dia.com>
> Cc: Alexandre Courbot <gnurou@...il.com>
> ---
> Applies on next-20141209.
> Intended for v3.20.
> Boot-tested on Tegra124 Jetson TK1 on next-20141209.
> Also boot-tested on Tegra132 Norrin FFD on next-20141209 + some unrelated 
> patches.
> 
>  drivers/soc/tegra/pmc.c | 7 +++++--
>  include/soc/tegra/pm.h  | 2 +-
>  2 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
> index a2c0ceb95f8f..4bdc654bd747 100644
> --- a/drivers/soc/tegra/pmc.c
> +++ b/drivers/soc/tegra/pmc.c
> @@ -739,7 +739,7 @@ static int tegra_pmc_probe(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_PM_SLEEP
> +#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_ARM)

I would slightly prefer having this as separate #ifdef lines to make it
clearer that we're special-casing 32-bit ARM.

>  static int tegra_pmc_suspend(struct device *dev)
>  {
>  	tegra_pmc_writel(virt_to_phys(tegra_resume), PMC_SCRATCH41);
> @@ -753,10 +753,11 @@ static int tegra_pmc_resume(struct device *dev)
>  
>  	return 0;
>  }
> -#endif
>  
>  static SIMPLE_DEV_PM_OPS(tegra_pmc_pm_ops, tegra_pmc_suspend, tegra_pmc_resume);
>  
> +#endif

I don't think this is necessary, SIMPLE_DEV_PM_OPS will not use the
supend or resume hooks if PM_SLEEP is disabled. The result will be an
empty dev_pm_ops structure. While that's somewhat useless, at least
it'll allow...

> +
>  static const char * const tegra20_powergates[] = {
>  	[TEGRA_POWERGATE_CPU] = "cpu",
>  	[TEGRA_POWERGATE_3D] = "3d",
> @@ -894,7 +895,9 @@ static struct platform_driver tegra_pmc_driver = {
>  		.name = "tegra-pmc",
>  		.suppress_bind_attrs = true,
>  		.of_match_table = tegra_pmc_match,
> +#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_ARM)
>  		.pm = &tegra_pmc_pm_ops,
> +#endif

... this #ifdef to be avoided.

>  	},
>  	.probe = tegra_pmc_probe,
>  };
> diff --git a/include/soc/tegra/pm.h b/include/soc/tegra/pm.h
> index 30fe2078a547..03909101d4e7 100644
> --- a/include/soc/tegra/pm.h
> +++ b/include/soc/tegra/pm.h
> @@ -17,7 +17,7 @@ enum tegra_suspend_mode {
>  	TEGRA_MAX_SUSPEND_MODE,
>  };
>  
> -#ifdef CONFIG_PM_SLEEP
> +#if defined(CONFIG_PM_SLEEP) && defined(CONFIG_ARM)

Similarly to the above, I'd prefer this to be two separate lines. That
also has the advantage that if we do add code for suspend/resume on 64
bit ARM later on we don't need to untangle the conditional again.

Thierry

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