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Date: Sun, 27 Nov 2016 17:09:07 +0100
From: Boris Brezillon <boris.brezillon@...e-electrons.com>
To: Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc: linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
Marek Vasut <marek.vasut@...il.com>,
Brian Norris <computersforpeace@...il.com>,
Richard Weinberger <richard@....at>,
David Woodhouse <dwmw2@...radead.org>,
Cyrille Pitchen <cyrille.pitchen@...el.com>
Subject: Re: [PATCH 17/39] mtd: nand: denali: support HW_ECC_FIXUP
capability
On Sun, 27 Nov 2016 03:06:03 +0900
Masahiro Yamada <yamada.masahiro@...ionext.com> wrote:
> Some old versions of the Denali IP (perhaps used only for Intel?)
> detects ECC errors and provides correct data via a register, but
> does not touch the transferred data. So, the software must fixup
> the data in the buffer according to the provided ECC correction
> information.
>
> Newer versions perform ECC correction before transferring the data.
> No more software intervention is needed. The ECC_ERROR_ADDRESS and
> ECC_CORRECTION_INFO registers were deprecated. Instead, the number
> of corrected bit-flips can be read from the ECC_COR_INFO register.
> When an uncorrectable ECC error happens, a status flag is set to the
> INTR_STATUS and ECC_COR_INFO registers.
>
> As is often the case with this IP, the register view of INTR_STATUS
> had broken compatibility.
>
> For older versions (SW ECC fixup):
> bit 0: ECC_TRANSACTION_DONE
> bit 1: ECC_ERR
>
> For newer versions (HW ECC fixup):
> bit 0: ECC_UNCOR_ERR
> bit 1: Reserved
>
> Due to this difference, the irq_mask must be fixed too. The comment
> block in the denali_sw_ecc_fixup() has been moved to the common part
> because the comment applies to both cases.
>
> The U-Boot port of this driver already supports the HW ECC fixup. I
> borrowed the comment "Some versions of ..." in denali.h from U-Boot.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
> drivers/mtd/nand/denali.c | 44 ++++++++++++++++++++++++++++++++++----------
> drivers/mtd/nand/denali.h | 14 ++++++++++++++
> 2 files changed, 48 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
> index 271b41a..c101e7f 100644
> --- a/drivers/mtd/nand/denali.c
> +++ b/drivers/mtd/nand/denali.c
> @@ -894,6 +894,25 @@ static bool is_erased(u8 *buf, int len)
> return false;
> return true;
> }
> +
> +static bool denali_hw_ecc_fixup(struct denali_nand_info *denali,
> + unsigned int *max_bitflips)
> +{
> + int bank = denali->flash_bank;
> + u32 ecc_cor;
> +
> + ecc_cor = ioread32(denali->flash_reg + ECC_COR_INFO(bank));
> + ecc_cor >>= ECC_COR_INFO_SHIFT(bank);
> +
> + if (ecc_cor & ECC_COR_INFO__UNCOR_ERR) {
> + *max_bitflips = 0;
> + return true;
> + }
> +
> + *max_bitflips = ecc_cor & ECC_COR_INFO__MAX_ERRORS;
> + return false;
> +}
> +
> #define ECC_SECTOR_SIZE 512
>
> #define ECC_SECTOR(x) (((x) & ECC_ERROR_ADDRESS__SECTOR_NR) >> 12)
> @@ -949,11 +968,6 @@ static bool denali_sw_ecc_fixup(struct denali_nand_info *denali, u8 *buf,
> bitflips++;
> }
> } else {
> - /*
> - * if the error is not correctable, need to look at the
> - * page to see if it is an erased page. if so, then
> - * it's not a real ECC error
> - */
> check_erased_page = true;
> }
> } while (!ECC_LAST_ERR(err_correction_info));
> @@ -1109,12 +1123,12 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
> {
> unsigned int max_bitflips;
> struct denali_nand_info *denali = mtd_to_denali(mtd);
> -
> dma_addr_t addr = denali->buf.dma_buf;
> size_t size = mtd->writesize + mtd->oobsize;
> -
> u32 irq_status;
> - u32 irq_mask = INTR_STATUS__ECC_TRANSACTION_DONE | INTR_STATUS__ECC_ERR;
> + u32 irq_mask = denali->caps & DENALI_CAPS_HW_ECC_FIXUP ?
> + INTR_STATUS__DMA_CMD_COMP | INTR_STATUS__ECC_UNCOR_ERR :
> + INTR_STATUS__ECC_TRANSACTION_DONE | INTR_STATUS__ECC_ERR;
> bool check_erased_page = false;
>
> if (page != denali->page) {
> @@ -1139,11 +1153,21 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
>
> memcpy(buf, denali->buf.buf, mtd->writesize);
>
> - check_erased_page = denali_sw_ecc_fixup(denali, buf, irq_status,
> - &max_bitflips);
> + if (denali->caps & DENALI_CAPS_HW_ECC_FIXUP)
> + check_erased_page = denali_hw_ecc_fixup(denali, &max_bitflips);
> + else
> + check_erased_page = denali_sw_ecc_fixup(denali, buf, irq_status,
> + &max_bitflips);
Okay, so you currently have two ways of handling ECC errors. What if a
new revision introduces yet another way to do it?
How about making denali_caps a structure where you have one (or several)
function pointers to implement operations differently depending on the
IP revision?
struct denali_caps {
u32 feature_flags; /* If needed. */
bool (*handle_ecc)(...);
...
};
> +
> denali_enable_dma(denali, false);
>
> if (check_erased_page) {
> + /*
> + * If the error is not correctable, need to look at the page to
> + * see if it is an erased page. If so, then it's not a real ECC
> + * error.
> + */
> +
> read_oob_data(mtd, chip->oob_poi, denali->page);
>
> /* check ECC failures that may have occurred on erased pages */
> diff --git a/drivers/mtd/nand/denali.h b/drivers/mtd/nand/denali.h
> index 69314d0..beadc8a 100644
> --- a/drivers/mtd/nand/denali.h
> +++ b/drivers/mtd/nand/denali.h
> @@ -20,6 +20,7 @@
> #ifndef __DENALI_H__
> #define __DENALI_H__
>
> +#include <linux/bitops.h>
> #include <linux/mtd/nand.h>
>
> #define DEVICE_RESET 0x0
> @@ -219,6 +220,13 @@
> #define INTR_STATUS(__bank) (0x410 + ((__bank) * 0x50))
> #define INTR_EN(__bank) (0x420 + ((__bank) * 0x50))
>
> +/*
> + * Some versions of the IP have the ECC fixup handled in hardware. In this
> + * configuration we only get interrupted when the error is uncorrectable.
> + * Unfortunately this bit replaces INTR_STATUS__ECC_TRANSACTION_DONE from the
> + * old IP.
> + */
> +#define INTR_STATUS__ECC_UNCOR_ERR 0x0001
> #define INTR_STATUS__ECC_TRANSACTION_DONE 0x0001
> #define INTR_STATUS__ECC_ERR 0x0002
> #define INTR_STATUS__DMA_CMD_COMP 0x0004
> @@ -297,6 +305,11 @@
> #define ERR_CORRECTION_INFO__ERROR_TYPE 0x4000
> #define ERR_CORRECTION_INFO__LAST_ERR_INFO 0x8000
>
> +#define ECC_COR_INFO(__bank) (0x650 + (__bank) / 2 * 0x10)
> +#define ECC_COR_INFO_SHIFT(__bank) ((__bank) % 2 * 8)
> +#define ECC_COR_INFO__MAX_ERRORS 0x007f
> +#define ECC_COR_INFO__UNCOR_ERR 0x0080
> +
> #define DMA_ENABLE 0x700
> #define DMA_ENABLE__FLAG 0x0001
>
> @@ -421,6 +434,7 @@ struct denali_nand_info {
> u32 bbtskipbytes;
> u32 max_banks;
> unsigned int caps;
> +#define DENALI_CAPS_HW_ECC_FIXUP BIT(0)
> };
>
> extern int denali_init(struct denali_nand_info *denali);
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