linux-kernel - Re: [PATCH 11/12] mtd: rawnand: brcmnand: Add support for getting ecc setting from strap

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Date:   Wed, 7 Jun 2023 10:25:24 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     William Zhang <william.zhang@...adcom.com>
Cc:     Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        Linux MTD List <linux-mtd@...ts.infradead.org>,
        f.fainelli@...il.com, rafal@...ecki.pl, kursad.oney@...adcom.com,
        joel.peshkin@...adcom.com, computersforpeace@...il.com,
        anand.gore@...adcom.com, dregan@...l.com, kamal.dasu@...adcom.com,
        tomer.yacoby@...adcom.com, dan.beygelman@...adcom.com,
        linux-kernel@...r.kernel.org,
        Vignesh Raghavendra <vigneshr@...com>,
        Richard Weinberger <richard@....at>,
        Kamal Dasu <kdasu.kdev@...il.com>
Subject: Re: [PATCH 11/12] mtd: rawnand: brcmnand: Add support for getting
 ecc setting from strap

Hi William,

william.zhang@...adcom.com wrote on Tue,  6 Jun 2023 16:12:51 -0700:

> BCMBCA broadband SoC based board design does not specify ecc setting in
> dts but rather use the SoC NAND strap info to obtain the ecc strength
> and spare area size setting. Add brcm,nand-ecc-use-strap dts propety for
> this purpose and update driver to support this option.
> 
> The generic nand ecc settings still take precedence over this flag. For
> example, if nand-ecc-strength is set in the dts, the driver ignores the
> strap setting and falls back to original behavior. This makes sure that
> the existing BCMBCA board dts still works the old way even the strap
> flag is set in the BCMBCA chip dtsi.
> 
> Signed-off-by: William Zhang <william.zhang@...adcom.com>
> ---
> 
>  drivers/mtd/nand/raw/brcmnand/brcmnand.c | 72 +++++++++++++++++++++---
>  1 file changed, 64 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> index 656be4d73016..8c7cea36ac71 100644
> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
> @@ -1076,6 +1076,38 @@ static void brcmnand_set_sector_size_1k(struct brcmnand_host *host, int val)
>  	nand_writereg(ctrl, acc_control_offs, tmp);
>  }
>  
> +static int brcmnand_get_spare_size(struct brcmnand_host *host)
> +{
> +	struct brcmnand_controller *ctrl = host->ctrl;
> +	u16 acc_control_offs = brcmnand_cs_offset(ctrl, host->cs,
> +						  BRCMNAND_CS_ACC_CONTROL);
> +	u32 acc = nand_readreg(ctrl, acc_control_offs);
> +
> +	return (acc&brcmnand_spare_area_mask(ctrl));
> +}
> +
> +static int brcmnand_get_ecc_strength(struct brcmnand_host *host)
> +{
> +	struct brcmnand_controller *ctrl = host->ctrl;
> +	u16 acc_control_offs = brcmnand_cs_offset(ctrl, host->cs,
> +						  BRCMNAND_CS_ACC_CONTROL);
> +	int sector_size_1k = brcmnand_get_sector_size_1k(host);
> +	int spare_area_size, ecc_level, ecc_strength;
> +	u32 acc;
> +
> +	spare_area_size = brcmnand_get_spare_size(host);
> +	acc = nand_readreg(ctrl, acc_control_offs);
> +	ecc_level = (acc & brcmnand_ecc_level_mask(ctrl)) >> brcmnand_ecc_level_shift(ctrl);
> +	if (sector_size_1k)
> +		ecc_strength = ecc_level<<1;

                                          ?

If you mean "x2" then let the compiler do that.

> +	else if (spare_area_size == 16 && ecc_level == 15)
> +		ecc_strength = 1; /* hamming */
> +	else
> +		ecc_strength = ecc_level;
> +
> +	return ecc_strength;
> +}
> +
>  /***********************************************************************
>   * CS_NAND_SELECT
>   ***********************************************************************/
> @@ -2656,19 +2688,43 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
>  		nanddev_get_ecc_requirements(&chip->base);
>  	struct brcmnand_controller *ctrl = host->ctrl;
>  	struct brcmnand_cfg *cfg = &host->hwcfg;
> -	char msg[128];
> +	struct device_node *np = nand_get_flash_node(chip);
>  	u32 offs, tmp, oob_sector;
> -	int ret;
> +	int ret, sector_size_1k = 0;
> +	bool use_strap = false;
> +	char msg[128];
>  
>  	memset(cfg, 0, sizeof(*cfg));
> +	use_strap = of_property_read_bool(np, "brcm,nand-ecc-use-strap");
> +
> +	/*
> +	 * Set ECC size and strength based on hw configuration from strap
> +	 * if device tree does not specify them and use strap property is set
> +	 * If ecc strength is set in dts, don't use strap setting.
> +	 */
> +	if (chip->ecc.strength)
> +		use_strap = 0;
> +
> +	if (use_strap) {
> +		chip->ecc.strength = brcmnand_get_ecc_strength(host);
> +		sector_size_1k = brcmnand_get_sector_size_1k(host);
> +		if (chip->ecc.size == 0) {
> +			if (sector_size_1k < 0)
> +				chip->ecc.size = 512;
> +			else
> +				chip->ecc.size = 512<<sector_size_1k;

Please run checkpatch.pl --strict

> +		}
> +	}
>  
> -	ret = of_property_read_u32(nand_get_flash_node(chip),
> -				   "brcm,nand-oob-sector-size",
> -				   &oob_sector);
> +	ret = of_property_read_u32(np, "brcm,nand-oob-sector-size",
> +			   &oob_sector);
>  	if (ret) {
> -		/* Use detected size */
> -		cfg->spare_area_size = mtd->oobsize /
> -					(mtd->writesize >> FC_SHIFT);
> +		if (use_strap)
> +			cfg->spare_area_size = brcmnand_get_spare_size(host);
> +		else
> +			/* Use detected size */
> +			cfg->spare_area_size = mtd->oobsize /
> +						(mtd->writesize >> FC_SHIFT);
>  	} else {
>  		cfg->spare_area_size = oob_sector;
>  	}


Thanks,
Miquèl