linux-kernel - Re: [PATCH v3 1/6] clk: sunxi-ng: a20: Register regmap for sun7i CCU

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Date:   Thu, 30 Apr 2020 16:51:38 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Priit Laes <plaes@...es.org>
Cc:     Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-sunxi@...glegroups.com
Subject: Re: [PATCH v3 1/6] clk: sunxi-ng: a20: Register regmap for sun7i CCU

On Thu, Apr 30, 2020 at 02:56:57PM +0300, Priit Laes wrote:
> On sun7i, the gmac clock is handled by the dwmac-sunxi driver, but
> its configuration register is located in the CCU register range,
> requiring proper regmap setup.
> 
> In order to do that, we use CLK_OF_DECLARE_DRIVER to initialize
> sun7i ccu, which clears the OF_POPULATED flag, allowing the
> platform device to probe the same resource with proper device node.
> 
> Signed-off-by: Priit Laes <plaes@...es.org>
> ---
>  drivers/clk/sunxi-ng/ccu-sun4i-a10.c | 62 +++++++++++++++++++++++++++-
>  1 file changed, 60 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/sunxi-ng/ccu-sun4i-a10.c b/drivers/clk/sunxi-ng/ccu-sun4i-a10.c
> index f32366d9336e..fa147b8ce705 100644
> --- a/drivers/clk/sunxi-ng/ccu-sun4i-a10.c
> +++ b/drivers/clk/sunxi-ng/ccu-sun4i-a10.c
> @@ -8,6 +8,8 @@
>  #include <linux/clk-provider.h>
>  #include <linux/io.h>
>  #include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/regmap.h>
>  
>  #include "ccu_common.h"
>  #include "ccu_reset.h"
> @@ -1478,5 +1480,61 @@ static void __init sun7i_a20_ccu_setup(struct device_node *node)
>  {
>  	sun4i_ccu_init(node, &sun7i_a20_ccu_desc);
>  }
> -CLK_OF_DECLARE(sun7i_a20_ccu, "allwinner,sun7i-a20-ccu",
> -	       sun7i_a20_ccu_setup);
> +CLK_OF_DECLARE_DRIVER(sun7i_a20_ccu, "allwinner,sun7i-a20-ccu",
> +		      sun7i_a20_ccu_setup);
> +
> +/*
> + * Regmap for the GMAC driver (dwmac-sunxi) to allow access to
> + * GMAC configuration register.
> + */
> +#define SUN7I_A20_GMAC_CFG_REG 0x164
> +static bool sun7i_a20_ccu_regmap_accessible_reg(struct device *dev,
> +						unsigned int reg)
> +{
> +	if (reg == SUN7I_A20_GMAC_CFG_REG)
> +		return true;
> +	return false;
> +}
> +
> +static struct regmap_config sun7i_a20_ccu_regmap_config = {
> +	.reg_bits	= 32,
> +	.val_bits	= 32,
> +	.reg_stride	= 4,
> +	.max_register	= 0x1f4, /* clk_out_b */
> +
> +	.readable_reg	= sun7i_a20_ccu_regmap_accessible_reg,
> +	.writeable_reg	= sun7i_a20_ccu_regmap_accessible_reg,
> +};
> +
> +static int sun7i_a20_ccu_probe_regmap(struct platform_device *pdev)
> +{
> +	void __iomem *reg;
> +	struct resource *res;
> +	struct regmap *regmap;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	reg = devm_ioremap(&pdev->dev, res->start, resource_size(res));
> +	if (IS_ERR(reg))
> +		return PTR_ERR(reg);

You shouldn't really create a second mapping here but reuse the one you got in
sun7i_a20_ccu_setup, since that code expect to be the sole user of it.

Storing the virtual address in a global variable should work fine since we only
ever have a single instance of the controller

Maxime

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