linux-kernel - Re: [PATCH v2 3/3] mtd: rawnand: qcom: Add support for secure regions in NAND memory

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Date:   Thu, 25 Feb 2021 08:47:02 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     richard@....at, vigneshr@...com, robh+dt@...nel.org,
        linux-arm-msm@...r.kernel.org, linux-mtd@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        boris.brezillon@...labora.com, Daniele.Palmas@...it.com,
        bjorn.andersson@...aro.org
Subject: Re: [PATCH v2 3/3] mtd: rawnand: qcom: Add support for secure
 regions in NAND memory

Hi Manivannan,

Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org> wrote on Thu,
25 Feb 2021 09:41:29 +0530:

> On a typical end product, a vendor may choose to secure some regions in
> the NAND memory which are supposed to stay intact between FW upgrades.
> The access to those regions will be blocked by a secure element like
> Trustzone. So the normal world software like Linux kernel should not
> touch these regions (including reading).
> 
> The regions are declared using a NAND chip DT property,
> "nand-secure-regions". So let's make use of this property and skip
> access to the secure regions present in a system.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---

[...]

>  	config_nand_page_write(nandc);
> @@ -2830,7 +2865,8 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
>  	struct nand_chip *chip = &host->chip;
>  	struct mtd_info *mtd = nand_to_mtd(chip);
>  	struct device *dev = nandc->dev;
> -	int ret;
> +	struct property *prop;
> +	int ret, length, nr_elem;
>  
>  	ret = of_property_read_u32(dn, "reg", &host->cs);
>  	if (ret) {
> @@ -2886,6 +2922,24 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
>  		}
>  	}
>  
> +	/*
> +	 * Look for secure regions in the NAND chip. These regions are supposed
> +	 * to be protected by a secure element like Trustzone. So the read/write
> +	 * accesses to these regions will be blocked in the runtime by this
> +	 * driver.
> +	 */
> +	prop = of_find_property(dn, "nand-secure-regions", &length);

I'm not sure the nand- prefix on this property is needed here, but
whatever.

> +	if (prop) {
> +		nr_elem = length / sizeof(u32);
> +		host->nr_sec_regions = nr_elem / 2;
> +
> +		host->sec_regions = devm_kcalloc(dev, nr_elem, sizeof(u32), GFP_KERNEL);
> +		if (!host->sec_regions)
> +			return -ENOMEM;
> +
> +		of_property_read_u32_array(dn, "nand-secure-regions", host->sec_regions, nr_elem);
> +	}
> +

I would move this before nand_scan().

If you don't, you should bail out with a nand_cleanup() upon error.

>  	ret = mtd_device_parse_register(mtd, probes, NULL, NULL, 0);
>  	if (ret)
>  		nand_cleanup(chip);


Otherwise lgtm.

Thanks,
Miquèl