linux-kernel - Re: [PATCH 01/16] ARM: scu: Provide support for parsing SCU device node to enable SCU

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Date:   Mon, 14 Nov 2016 14:12:51 +0800
From:   Jisheng Zhang <jszhang@...vell.com>
To:     Pankaj Dubey <pankaj.dubey@...sung.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <rmk+kernel@...linux.org.uk>,
        <arnd@...db.de>, <horms@...ge.net.au>, <magnus.damm@...il.com>,
        <geert+renesas@...der.be>, <vireshk@...nel.org>,
        <shiraz.linux.kernel@...il.com>, <krzk@...nel.org>,
        <thomas.ab@...sung.com>, Russell King <linux@...linux.org.uk>,
        Dinh Nguyen <dinguyen@...nsource.altera.com>,
        Patrice Chotard <patrice.chotard@...com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Liviu Dudau <liviu.dudau@....com>, Ray Jui <rjui@...adcom.com>,
        Stephen Warren <swarren@...dotorg.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Shawn Guo <shawnguo@...nel.org>,
        Michal Simek <michal.simek@...inx.com>,
        Wei Xu <xuwei5@...ilicon.com>, Andrew Lunn <andrew@...n.ch>,
        Jun Nie <jun.nie@...aro.org>
Subject: Re: [PATCH 01/16] ARM: scu: Provide support for parsing SCU device
 node to enable SCU

Hi Pankaj,

On Mon, 14 Nov 2016 10:31:56 +0530 Pankaj Dubey wrote:

> Many platforms are duplicating code for enabling SCU, lets add
> common code to enable SCU by parsing SCU device node so the duplication
> in each platform can be avoided.
> 
> CC: Krzysztof Kozlowski <krzk@...nel.org>
> CC: Jisheng Zhang <jszhang@...vell.com>
> CC: Russell King <linux@...linux.org.uk>
> CC: Dinh Nguyen <dinguyen@...nsource.altera.com>
> CC: Patrice Chotard <patrice.chotard@...com>
> CC: Linus Walleij <linus.walleij@...aro.org>
> CC: Liviu Dudau <liviu.dudau@....com>
> CC: Ray Jui <rjui@...adcom.com>
> CC: Stephen Warren <swarren@...dotorg.org>
> CC: Heiko Stuebner <heiko@...ech.de>
> CC: Shawn Guo <shawnguo@...nel.org>
> CC: Michal Simek <michal.simek@...inx.com>
> CC: Wei Xu <xuwei5@...ilicon.com>
> CC: Andrew Lunn <andrew@...n.ch>
> CC: Jun Nie <jun.nie@...aro.org> 
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Pankaj Dubey <pankaj.dubey@...sung.com>
> ---
>  arch/arm/include/asm/smp_scu.h |  4 +++
>  arch/arm/kernel/smp_scu.c      | 56 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+)
> 
> diff --git a/arch/arm/include/asm/smp_scu.h b/arch/arm/include/asm/smp_scu.h
> index bfe163c..fdeec07 100644
> --- a/arch/arm/include/asm/smp_scu.h
> +++ b/arch/arm/include/asm/smp_scu.h
> @@ -39,8 +39,12 @@ static inline int scu_power_mode(void __iomem *scu_base, unsigned int mode)
>  
>  #if defined(CONFIG_SMP) && defined(CONFIG_HAVE_ARM_SCU)
>  void scu_enable(void __iomem *scu_base);
> +void __iomem *of_scu_get_base(void);
> +int of_scu_enable(void);
>  #else
>  static inline void scu_enable(void __iomem *scu_base) {}
> +static inline void __iomem *of_scu_get_base(void) {return NULL; }
> +static inline int of_scu_enable(void) {return 0; }
>  #endif
>  
>  #endif
> diff --git a/arch/arm/kernel/smp_scu.c b/arch/arm/kernel/smp_scu.c
> index 72f9241..d0ac3ed 100644
> --- a/arch/arm/kernel/smp_scu.c
> +++ b/arch/arm/kernel/smp_scu.c
> @@ -10,6 +10,7 @@
>   */
>  #include <linux/init.h>
>  #include <linux/io.h>
> +#include <linux/of_address.h>
>  
>  #include <asm/smp_plat.h>
>  #include <asm/smp_scu.h>
> @@ -70,6 +71,61 @@ void scu_enable(void __iomem *scu_base)
>  	 */
>  	flush_cache_all();
>  }
> +
> +static const struct of_device_id scu_match[] = {
> +	{ .compatible = "arm,cortex-a9-scu", },
> +	{ .compatible = "arm,cortex-a5-scu", },
> +	{ }
> +};
> +
> +/*
> + * Helper API to get SCU base address
> + * In case platform DT do not have SCU node, or iomap fails
> + * this call will fallback and will try to map via call to
> + * scu_a9_get_base.
> + * This will return ownership of scu_base to the caller
> + */
> +void __iomem *of_scu_get_base(void)
> +{
> +	unsigned long base = 0;
> +	struct device_node *np;
> +	void __iomem *scu_base;
> +
> +	np = of_find_matching_node(NULL, scu_match);

could we check np before calling of_iomap()?

> +	scu_base = of_iomap(np, 0);
> +	of_node_put(np);
> +	if (!scu_base) {
> +		pr_err("%s failed to map scu_base via DT\n", __func__);

For non-ca5, non-ca9 based SoCs, we'll see this error msg. We understand
what does it mean, but it may confuse normal users. In current version,
berlin doesn't complain like this for non-ca9 SoCs

> +		if (scu_a9_has_base()) {
> +			base = scu_a9_get_base();
> +			scu_base = ioremap(base, SZ_4K);
> +		}
> +		if (!scu_base) {
> +			pr_err("%s failed to map scu_base\n", __func__);

ditto

> +			return IOMEM_ERR_PTR(-ENOMEM);
> +		}
> +	}
> +	return scu_base;
> +}
> +
> +/*
> + * Enable SCU via mapping scu_base DT
> + * If scu_base mapped successfully scu will be enabled and in case of
> + * failure if will return non-zero error code
> + */
> +int of_scu_enable(void)
> +{
> +	void __iomem *scu_base;
> +
> +	scu_base = of_scu_get_base();
> +	if (!IS_ERR(scu_base)) {
> +		scu_enable(scu_base);
> +		iounmap(scu_base);
> +		return 0;
> +	}
> +	return PTR_ERR(scu_base);
> +}
> +
>  #endif
>  
>  /*