[PATCH v2] mtd: rawnand: Ensure the nand chip supports cached reads

[Rouven Czerwinski]

Both the JEDEC and ONFI specification say that read cache sequential
support is an optional command. This means that we not only need to
check whether the individual controller supports the command, we also
need to check the parameter pages for both ONFI and JEDEC NAND flashes
before enabling sequential cache reads.

This fixes support for NAND flashes which don't support enabling cache
reads, i.e. Samsung K9F4G08U0F or Toshiba TC58NVG0S3HTA00.

Sequential cache reads are now only available for ONFI and JEDEC
devices, if individual vendors implement this, it needs to be enabled
per vendor.

Tested on i.MX6Q with a Samsung NAND flash chip that doesn't support
sequential reads.

Fixes: 003fe4b9545b ("mtd: rawnand: Support for sequential cache reads")
Cc: stable at vger.kernel.org
Signed-off-by: Rouven Czerwinski <r.czerwinski at pengutronix.de>
---
v2:
- change title as suggested by Miquel
- adjust controller sentence from implement to support
- fix missing true assignement for flashes
- add CC stable instead of empty line
- add documentation comment for new supports_read_cache bool inside
  nand parameter struct

 drivers/mtd/nand/raw/nand_base.c  | 3 +++
 drivers/mtd/nand/raw/nand_jedec.c | 3 +++
 drivers/mtd/nand/raw/nand_onfi.c  | 3 +++
 include/linux/mtd/jedec.h         | 3 +++
 include/linux/mtd/onfi.h          | 1 +
 include/linux/mtd/rawnand.h       | 2 ++
 6 files changed, 15 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index d4b55155aeae..1fcac403cee6 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -5110,6 +5110,9 @@ static void rawnand_check_cont_read_support(struct nand_chip *chip)
 {
 	struct mtd_info *mtd = nand_to_mtd(chip);
 
+	if (!chip->parameters.supports_read_cache)
+		return;
+
 	if (chip->read_retries)
 		return;
 
diff --git a/drivers/mtd/nand/raw/nand_jedec.c b/drivers/mtd/nand/raw/nand_jedec.c
index 836757717660..b3cc8f360529 100644
--- a/drivers/mtd/nand/raw/nand_jedec.c
+++ b/drivers/mtd/nand/raw/nand_jedec.c
@@ -94,6 +94,9 @@ int nand_jedec_detect(struct nand_chip *chip)
 		goto free_jedec_param_page;
 	}
 
+	if (p->opt_cmd[0] & JEDEC_OPT_CMD_READ_CACHE)
+		chip->parameters.supports_read_cache = true;
+
 	memorg->pagesize = le32_to_cpu(p->byte_per_page);
 	mtd->writesize = memorg->pagesize;
 
diff --git a/drivers/mtd/nand/raw/nand_onfi.c b/drivers/mtd/nand/raw/nand_onfi.c
index f15ef90aec8c..861975e44b55 100644
--- a/drivers/mtd/nand/raw/nand_onfi.c
+++ b/drivers/mtd/nand/raw/nand_onfi.c
@@ -303,6 +303,9 @@ int nand_onfi_detect(struct nand_chip *chip)
 			   ONFI_FEATURE_ADDR_TIMING_MODE, 1);
 	}
 
+	if (le16_to_cpu(p->opt_cmd) & ONFI_OPT_CMD_READ_CACHE)
+		chip->parameters.supports_read_cache = true;
+
 	onfi = kzalloc(sizeof(*onfi), GFP_KERNEL);
 	if (!onfi) {
 		ret = -ENOMEM;
diff --git a/include/linux/mtd/jedec.h b/include/linux/mtd/jedec.h
index 0b6b59f7cfbd..56047a4e54c9 100644
--- a/include/linux/mtd/jedec.h
+++ b/include/linux/mtd/jedec.h
@@ -21,6 +21,9 @@ struct jedec_ecc_info {
 /* JEDEC features */
 #define JEDEC_FEATURE_16_BIT_BUS	(1 << 0)
 
+/* JEDEC Optional Commands */
+#define JEDEC_OPT_CMD_READ_CACHE	BIT(1)
+
 struct nand_jedec_params {
 	/* rev info and features block */
 	/* 'J' 'E' 'S' 'D'  */
diff --git a/include/linux/mtd/onfi.h b/include/linux/mtd/onfi.h
index a7376f9beddf..55ab2e4d62f9 100644
--- a/include/linux/mtd/onfi.h
+++ b/include/linux/mtd/onfi.h
@@ -55,6 +55,7 @@
 #define ONFI_SUBFEATURE_PARAM_LEN	4
 
 /* ONFI optional commands SET/GET FEATURES supported? */
+#define ONFI_OPT_CMD_READ_CACHE		BIT(1)
 #define ONFI_OPT_CMD_SET_GET_FEATURES	BIT(2)
 
 struct nand_onfi_params {
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index 90a141ba2a5a..c29ace15a053 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -225,6 +225,7 @@ struct gpio_desc;
  * struct nand_parameters - NAND generic parameters from the parameter page
  * @model: Model name
  * @supports_set_get_features: The NAND chip supports setting/getting features
+ * @supports_read_cache: The NAND chip supports read cache operations
  * @set_feature_list: Bitmap of features that can be set
  * @get_feature_list: Bitmap of features that can be get
  * @onfi: ONFI specific parameters
@@ -233,6 +234,7 @@ struct nand_parameters {
 	/* Generic parameters */
 	const char *model;
 	bool supports_set_get_features;
+	bool supports_read_cache;
 	DECLARE_BITMAP(set_feature_list, ONFI_FEATURE_NUMBER);
 	DECLARE_BITMAP(get_feature_list, ONFI_FEATURE_NUMBER);
 

base-commit: 42dc814987c1feb6410904e58cfd4c36c4146150
-- 
2.42.0