linux-kernel - Re: [PATCH] memory: jz4780_nemc: Only request IO memory the driver will use

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Date:   Tue, 28 Jul 2020 11:21:50 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     od@...c.me, linux-kernel@...r.kernel.org,
        "H . Nikolaus Schaller" <hns@...delico.com>
Subject: Re: [PATCH] memory: jz4780_nemc: Only request IO memory the driver
 will use

On Mon, Jul 27, 2020 at 06:20:34PM +0200, Paul Cercueil wrote:
> The driver only uses the registers up to offset 0x54. Since the EFUSE
> registers are in the middle of the NEMC registers, we only request
> the registers we will use for now - that way the EFUSE driver can
> probe too.
> 
> Tested-by: H. Nikolaus Schaller <hns@...delico.com>
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  drivers/memory/jz4780-nemc.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/memory/jz4780-nemc.c b/drivers/memory/jz4780-nemc.c
> index b232ed279fc3..647267ea8c63 100644
> --- a/drivers/memory/jz4780-nemc.c
> +++ b/drivers/memory/jz4780-nemc.c
> @@ -8,6 +8,7 @@
>  
>  #include <linux/clk.h>
>  #include <linux/init.h>
> +#include <linux/io.h>
>  #include <linux/math64.h>
>  #include <linux/of.h>
>  #include <linux/of_address.h>
> @@ -288,7 +289,19 @@ static int jz4780_nemc_probe(struct platform_device *pdev)
>  	nemc->dev = dev;
>  
>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> -	nemc->base = devm_ioremap_resource(dev, res);
> +
> +	/*
> +	 * The driver only uses the registers up to offset 0x54. Since the EFUSE
> +	 * registers are in the middle of the NEMC registers, we only request
> +	 * the registers we will use for now - that way the EFUSE driver can
> +	 * probe too.
> +	 */
> +	if (!devm_request_mem_region(dev, res->start, 0x54, dev_name(dev))) {
> +		dev_err(dev, "unable to request I/O memory region\n");
> +		return -EBUSY;
> +	}
> +
> +	nemc->base = devm_ioremap(dev, res->start, resource_size(res));

Shouldn't you map only 0x54 size as well?

Best regards,
Krzysztof