Re: [PATCH v5 09/12] mtd: rawnand: brcmnand: Add support for getting ecc setting from strap

William Zhang
2024-02-23T03:35:58Z

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Hi Miquel,

On 2/20/24 01:53, Miquel Raynal wrote:
> Hi William,
>
> william.zhang@broadcom.com wrote on Wed, 7 Feb 2024 12:22:54 -0800:
>
>> 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@broadcom.com>
>> Reviewed-by: David Regan <dregan@broadcom.com>
>>
>> ---
>>
>> Changes in v5: None
>> Changes in v4:
>> - Update the comments for ecc setting selection
>>
>> Changes in v3: None
>> Changes in v2:
>> - Minor cosmetic fixes
>>
>> drivers/mtd/nand/raw/brcmnand/brcmnand.c | 83 ++++++++++++++++++++++--
>> 1 file changed, 76 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> index 73fdf7ce21aa..efeee9e80213 100644
>> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> @@ -1038,6 +1038,19 @@ static inline int brcmnand_sector_1k_shift(struct brcmnand_controller *ctrl)
>> return -1;
>> }
>>
>> +static int brcmnand_get_sector_size_1k(struct brcmnand_host *host)
>> +{
>> + struct brcmnand_controller *ctrl = host->ctrl;
>> + int shift = brcmnand_sector_1k_shift(ctrl);
>> + u16 acc_control_offs = brcmnand_cs_offset(ctrl, host->cs,
>> + BRCMNAND_CS_ACC_CONTROL);
>> +
>> + if (shift < 0)
>> + return 0;
>> +
>> + return (nand_readreg(ctrl, acc_control_offs) >> shift) & 0x1;
>
> What is this & 0x1 ? If you return a yes/no value, please make this
> function return a bool. Also, please use intermediate steps to clarify
> what you do.
>
> sector_1k_bit = ...;
> acc = nand_readreg();
> return acc & BIT(sector_1k_bit);
>
> Or something like that.
>
This sector 1k bit is just single bit field. But we do want to return
negative for error condition and 0 for 512 sector and 1 for 1K sector
size. Will add intermediate steps.

>> +}
>> +
>> static void brcmnand_set_sector_size_1k(struct brcmnand_host *host, int val)
>> {
>> struct brcmnand_controller *ctrl = host->ctrl;
>> @@ -1055,6 +1068,38 @@ 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)
>
> _from_strap
>
>> +{
>> + 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)) >> ctrl->ecc_level_shift;
>
> Please use FIELD_PREP/FIELD_GET.
>
These macros do not work here as the mask is not constant.

>> + if (sector_size_1k)
>> + ecc_strength = ecc_level * 2;
>> + else if (spare_area_size == 16 && ecc_level == 15)
>> + ecc_strength = 1; /* hamming */
>> + else
>> + ecc_strength = ecc_level;
>> +
>> + return ecc_strength;
>> +}
>> +
>> /***********************************************************************
>> * CS_NAND_SELECT
>> ***********************************************************************/
>> @@ -2622,19 +2667,43 @@ static int brcmnand_setup_dev(struct brcmnand_host *host)
>> nanddev_get_memorg(&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");
>>
>> - ret = of_property_read_u32(nand_get_flash_node(chip),
>> - "brcm,nand-oob-sector-size",
>> + /*
>> + * Set ECC size and strength based on hw configuration from strap
>> + * if brcm,nand-ecc-use-strap is set. However if nand-ecc-strength
>> + * is set, its value will be used and ignore the strap setting.
>
> Please error out in this case. It's one or the other, not both.
>
Will update.

>> + */
>> + 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;
>> + }
>
> I'd instead make a function named brcmnand_get_ecc_settings() with the
> chip->ecc parameter, so you can directly fill the entries without
> getting another time the sector_size_1k thing.
>
> Strength and step size are tightly linked, it does make sense to derive
> them both at the same time.
>
Will update.

>> + }
>> +
>> + 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

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