From ba84fb5952af114e28ac82adcdef75297701ccc1 Mon Sep 17 00:00:00 2001 From: Brian Norris Date: Fri, 3 Jan 2014 15:13:33 -0800 Subject: mtd: nand: add generic READ RETRY support Modern MLC (and even SLC?) NAND can experience a large number of bitflips (beyond the recommended correctability capacity) due to drifts in the voltage threshold (Vt). These bitflips can cause ECC errors to occur well within the expected lifetime of the flash. To account for this, some manufacturers provide a mechanism for shifting the Vt threshold after a corrupted read. The generic pattern seems to be that a particular flash has N read retry modes (where N = 0, traditionally), and after an ECC failure, the host should reconfigure the flash to use the next available mode, then retry the read operation. This process repeats until all bitfips can be corrected or until the host has tried all available retry modes. This patch adds the infrastructure support for a vendor-specific/flash-specific callback, used for setting the read-retry mode (i.e., voltage threshold). For now, this patch always returns the flash to mode 0 (the default mode) after a successful read-retry, according to the flowchart found in Micron's datasheets. This may need to change in the future if it is determined that eventually, mode 0 is insufficient for the majority of the flash cells (and so for performance reasons, we should leave the flash in mode 1, 2, etc.). Signed-off-by: Brian Norris Acked-by: Huang Shijie --- include/linux/mtd/nand.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/mtd') diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h index 029fe5948dc4..267d61dd89dd 100644 --- a/include/linux/mtd/nand.h +++ b/include/linux/mtd/nand.h @@ -472,6 +472,8 @@ struct nand_buffers { * commands to the chip. * @waitfunc: [REPLACEABLE] hardwarespecific function for wait on * ready. + * @setup_read_retry: [FLASHSPECIFIC] flash (vendor) specific function for + * setting the read-retry mode. Mostly needed for MLC NAND. * @ecc: [BOARDSPECIFIC] ECC control structure * @buffers: buffer structure for read/write * @hwcontrol: platform-specific hardware control structure @@ -518,6 +520,7 @@ struct nand_buffers { * non 0 if ONFI supported. * @onfi_params: [INTERN] holds the ONFI page parameter when ONFI is * supported, 0 otherwise. + * @read_retries: [INTERN] the number of read retry modes supported * @onfi_set_features: [REPLACEABLE] set the features for ONFI nand * @onfi_get_features: [REPLACEABLE] get the features for ONFI nand * @bbt: [INTERN] bad block table pointer @@ -565,6 +568,7 @@ struct nand_chip { int feature_addr, uint8_t *subfeature_para); int (*onfi_get_features)(struct mtd_info *mtd, struct nand_chip *chip, int feature_addr, uint8_t *subfeature_para); + int (*setup_read_retry)(struct mtd_info *mtd, int retry_mode); int chip_delay; unsigned int options; @@ -589,6 +593,8 @@ struct nand_chip { int onfi_version; struct nand_onfi_params onfi_params; + int read_retries; + flstate_t state; uint8_t *oob_poi; -- cgit v1.2.3