Re: [PATCH v4 3/3] mtd: rawnand: qcom: Add support for secure regions in NAND memory

[Boris Brezillon <boris.brezillon@collabora.com>]

On Mon,  8 Mar 2021 11:14:47 +0530
Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> wrote:

> 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,
> "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@linaro.org>
> ---
>  drivers/mtd/nand/raw/qcom_nandc.c | 72 +++++++++++++++++++++++++++----
>  1 file changed, 63 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/qcom_nandc.c b/drivers/mtd/nand/raw/qcom_nandc.c
> index 87c23bb320bf..8027f7cb32be 100644
> --- a/drivers/mtd/nand/raw/qcom_nandc.c
> +++ b/drivers/mtd/nand/raw/qcom_nandc.c
> @@ -431,6 +431,11 @@ struct qcom_nand_controller {
>   * @cfg0, cfg1, cfg0_raw..:	NANDc register configurations needed for
>   *				ecc/non-ecc mode for the current nand flash
>   *				device
> + *
> + * @sec_regions:		Array representing the secure regions in the
> + *				NAND chip
> + *
> + * @nr_sec_regions:		Number of secure regions in the NAND chip
>   */
>  struct qcom_nand_host {
>  	struct nand_chip chip;
> @@ -453,6 +458,9 @@ struct qcom_nand_host {
>  	u32 ecc_bch_cfg;
>  	u32 clrflashstatus;
>  	u32 clrreadstatus;
> +
> +	u32 *sec_regions;
> +	u8 nr_sec_regions;
>  };
>  
>  /*
> @@ -662,16 +670,27 @@ static void nandc_set_reg(struct qcom_nand_controller *nandc, int offset,
>  }
>  
>  /* helper to configure address register values */
> -static void set_address(struct qcom_nand_host *host, u16 column, int page)
> +static int set_address(struct qcom_nand_host *host, u16 column, int page)
>  {
>  	struct nand_chip *chip = &host->chip;
>  	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
> +	u32 offs = page << chip->page_shift;
> +	int i, j;
> +
> +	/* Skip touching the secure regions if present */
> +	for (i = 0, j = 0; i < host->nr_sec_regions; i++, j += 2) {
> +		if (offs >= host->sec_regions[j] &&
> +		    (offs <= host->sec_regions[j] + host->sec_regions[j + 1]))
> +			return -EIO;
> +	}

Hm, not sure that's a good idea to make this check part of
set_address(). Looks like set_address() can be used for ONFI page
access too, and you definitely don't want to block those
requests. I'd recommend having a separate helper that you can call from
qcom_nandc_{read,write}_{oob,page,page_raw}().

>  
>  	if (chip->options & NAND_BUSWIDTH_16)
>  		column >>= 1;
>  
>  	nandc_set_reg(nandc, NAND_ADDR0, page << 16 | column);
>  	nandc_set_reg(nandc, NAND_ADDR1, page >> 16 & 0xff);
> +
> +	return 0;
>  }
>  
>  /*
> @@ -1491,13 +1510,13 @@ static void qcom_nandc_command(struct nand_chip *chip, unsigned int command,
>  		WARN_ON(column != 0);
>  
>  		host->use_ecc = true;
> -		set_address(host, 0, page_addr);
> +		ret = set_address(host, 0, page_addr);
>  		update_rw_regs(host, ecc->steps, true);
>  		break;
>  
>  	case NAND_CMD_SEQIN:
>  		WARN_ON(column != 0);
> -		set_address(host, 0, page_addr);
> +		ret = set_address(host, 0, page_addr);
>  		break;
>  
>  	case NAND_CMD_PAGEPROG:
> @@ -1615,7 +1634,10 @@ qcom_nandc_read_cw_raw(struct mtd_info *mtd, struct nand_chip *chip,
>  	host->use_ecc = false;
>  
>  	clear_bam_transaction(nandc);
> -	set_address(host, host->cw_size * cw, page);
> +	ret = set_address(host, host->cw_size * cw, page);
> +	if (ret)
> +		return ret;
> +
>  	update_rw_regs(host, 1, true);
>  	config_nand_page_read(nandc);
>  
> @@ -1943,7 +1965,10 @@ static int copy_last_cw(struct qcom_nand_host *host, int page)
>  	/* prepare a clean read buffer */
>  	memset(nandc->data_buffer, 0xff, size);
>  
> -	set_address(host, host->cw_size * (ecc->steps - 1), page);
> +	ret = set_address(host, host->cw_size * (ecc->steps - 1), page);
> +	if (ret)
> +		return ret;
> +
>  	update_rw_regs(host, 1, true);
>  
>  	config_nand_single_cw_page_read(nandc, host->use_ecc);
> @@ -2005,12 +2030,16 @@ static int qcom_nandc_read_oob(struct nand_chip *chip, int page)
>  	struct qcom_nand_host *host = to_qcom_nand_host(chip);
>  	struct qcom_nand_controller *nandc = get_qcom_nand_controller(chip);
>  	struct nand_ecc_ctrl *ecc = &chip->ecc;
> +	int ret;
>  
>  	clear_read_regs(nandc);
>  	clear_bam_transaction(nandc);
>  
>  	host->use_ecc = true;
> -	set_address(host, 0, page);
> +	ret = set_address(host, 0, page);
> +	if (ret)
> +		return ret;
> +
>  	update_rw_regs(host, ecc->steps, true);
>  
>  	return read_page_ecc(host, NULL, chip->oob_poi, page);
> @@ -2188,7 +2217,10 @@ static int qcom_nandc_write_oob(struct nand_chip *chip, int page)
>  	mtd_ooblayout_get_databytes(mtd, nandc->data_buffer + data_size, oob,
>  				    0, mtd->oobavail);
>  
> -	set_address(host, host->cw_size * (ecc->steps - 1), page);
> +	ret = set_address(host, host->cw_size * (ecc->steps - 1), page);
> +	if (ret)
> +		return ret;
> +
>  	update_rw_regs(host, 1, false);
>  
>  	config_nand_page_write(nandc);
> @@ -2267,7 +2299,10 @@ static int qcom_nandc_block_markbad(struct nand_chip *chip, loff_t ofs)
>  
>  	/* prepare write */
>  	host->use_ecc = false;
> -	set_address(host, host->cw_size * (ecc->steps - 1), page);
> +	ret = set_address(host, host->cw_size * (ecc->steps - 1), page);
> +	if (ret)
> +		return ret;
> +
>  	update_rw_regs(host, 1, false);
>  
>  	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) {
> @@ -2872,6 +2908,24 @@ static int qcom_nand_host_init_and_register(struct qcom_nand_controller *nandc,
>  	/* set up initial status value */
>  	host->status = NAND_STATUS_READY | NAND_STATUS_WP;
>  
> +	/*
> +	 * 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, "secure-regions", &length);
> +	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, "secure-regions", host->sec_regions, nr_elem);
> +	}
> +
>  	ret = nand_scan(chip, 1);
>  	if (ret)
>  		return ret;