linux-kernel - Re: [PATCH 2/3] ARM: imx: add gpcv2 support

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Date:   Fri, 26 Aug 2016 12:17:58 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Anson Huang <Anson.Huang@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, shawnguo@...nel.org,
        kernel@...gutronix.de, fabio.estevam@....com, robh+dt@...nel.org,
        mark.rutland@....com
Subject: Re: [PATCH 2/3] ARM: imx: add gpcv2 support

On Fri, Aug 26, 2016 at 07:12:50PM +0800, Anson Huang wrote:
> diff --git a/arch/arm/mach-imx/gpcv2.c b/arch/arm/mach-imx/gpcv2.c
> new file mode 100644
> index 0000000..98577c4
> --- /dev/null
> +++ b/arch/arm/mach-imx/gpcv2.c
> @@ -0,0 +1,66 @@
> +/*
> + * Copyright 2016 Freescale Semiconductor, Inc.
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +
> +#include "common.h"
> +
> +#define GPC_CPU_PGC_SW_PUP_REQ	0xf0
> +#define GPC_CPU_PGC_SW_PDN_REQ	0xfc
> +#define GPC_PGC_C1		0x840
> +
> +#define BM_CPU_PGC_SW_PDN_PUP_REQ_CORE1_A7	0x2
> +#define BM_GPC_PGC_PCG				0x1
> +
> +static void __iomem *gpcv2_base;
> +
> +static void imx_gpcv2_set_m_core_pgc(bool enable, u32 offset)
> +{
> +	u32 val = readl_relaxed(gpcv2_base + offset) & (~BM_GPC_PGC_PCG);

Unnecessary parens, and the code doesn't flow with the bit clearance
here...

> +
> +	if (enable)
> +		val |= BM_GPC_PGC_PCG;

My first read of this lead me to think "okay, so what's the point of
enable=false".  It would be clearer with:

	u32 val = readl_relaxed(gpcv2_base + offset);

	if (enable)
		val |= BM_GPC_PGC_PCG;
	else
		val &= ~BM_GPC_PGC_PCG;

here.

> +
> +	writel_relaxed(val, gpcv2_base + offset);
> +}
> +
> +void imx_gpcv2_set_core1_pdn_pup_by_software(bool pdn)
> +{
> +	u32 val = readl_relaxed(gpcv2_base + (pdn ?
> +		GPC_CPU_PGC_SW_PDN_REQ : GPC_CPU_PGC_SW_PUP_REQ));
> +
> +	imx_gpcv2_set_m_core_pgc(true, GPC_PGC_C1);
> +	val |= BM_CPU_PGC_SW_PDN_PUP_REQ_CORE1_A7;
> +	writel_relaxed(val, gpcv2_base + (pdn ?
> +		GPC_CPU_PGC_SW_PDN_REQ : GPC_CPU_PGC_SW_PUP_REQ));
> +
> +	while ((readl_relaxed(gpcv2_base + (pdn ?
> +		GPC_CPU_PGC_SW_PDN_REQ : GPC_CPU_PGC_SW_PUP_REQ)) &
> +		BM_CPU_PGC_SW_PDN_PUP_REQ_CORE1_A7) != 0)
> +		;
> +	imx_gpcv2_set_m_core_pgc(false, GPC_PGC_C1);
> +}
> +
> +void __init imx_gpcv2_check_dt(void)
> +{
> +	struct device_node *np;
> +
> +	np = of_find_compatible_node(NULL, NULL, "fsl,imx7d-gpc");
> +	if (WARN_ON(!np))
> +		return;
> +
> +	gpcv2_base = of_iomap(np, 0);
> +	WARN_ON(!gpcv2_base);

What happens if gpcv2_base is NULL (apart from the obvious warning
from the above line)?  I guess a bit later in the boot,
imx_gpcv2_set_core1_pdn_pup_by_software() oopses the kernel,
probably before the console has been initialised.  Probably not
nice behaviour.

> +}
> -- 
> 1.9.1
> 

-- 
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