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mtd: devices: elm: check for hardware engine's design constraints

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ELM hardware engine is used by BCH ecc-schemes for detecting and locating ECC
errors. This patch adds the following checks for ELM hardware engine:

 - ELM internal buffers are of 1K,
   so it cannot process data with ecc-step-size > 1K.

 - ELM engine can execute upto maximum of 8 threads in parallel,
   so in *page-mode* (when complete page is processed in single iteration),
   ELM cannot support ecc-steps > 8.

Signed-off-by: Pekon Gupta <pekon@ti.com>
Reviewed-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
This commit is contained in:
Pekon Gupta 2014-03-20 18:48:34 +05:30 committed by Brian Norris
parent d9ba46d32c
commit 3f4eb14bdb
3 changed files with 20 additions and 5 deletions
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13
drivers/mtd/devices/elm.c
View File

@ -103,7 +103,8 @@ static u32 elm_read_reg(struct elm_info *info, int offset)
* @dev: ELM device
* @bch_type: Type of BCH ecc
*/
int elm_config(struct device *dev, enum bch_ecc bch_type)
int elm_config(struct device *dev, enum bch_ecc bch_type,
int ecc_steps, int ecc_step_size, int ecc_syndrome_size)
{
u32 reg_val;
struct elm_info *info = dev_get_drvdata(dev);
@ -112,6 +113,16 @@ int elm_config(struct device *dev, enum bch_ecc bch_type)
dev_err(dev, "Unable to configure elm - device not probed?\n");
return -ENODEV;
}
/* ELM cannot detect ECC errors for chunks > 1KB */
if (ecc_step_size > ((ELM_ECC_SIZE + 1) / 2)) {
dev_err(dev, "unsupported config ecc-size=%d\n", ecc_step_size);
return -EINVAL;
}
/* ELM support 8 error syndrome process */
if (ecc_steps > ERROR_VECTOR_MAX) {
dev_err(dev, "unsupported config ecc-step=%d\n", ecc_steps);
return -EINVAL;
}
reg_val = (bch_type & ECC_BCH_LEVEL_MASK) | (ELM_ECC_SIZE << 16);
elm_write_reg(info, ELM_LOCATION_CONFIG, reg_val);

9
drivers/mtd/nand/omap2.c
View File

@ -1540,6 +1540,8 @@ static int is_elm_present(struct omap_nand_info *info,
struct device_node *elm_node, enum bch_ecc bch_type)
{
struct platform_device *pdev;
struct nand_ecc_ctrl *ecc = &info->nand.ecc;
int err;
/* check whether elm-id is passed via DT */
if (!elm_node) {
pr_err("nand: error: ELM DT node not found\n");
@ -1553,9 +1555,10 @@ static int is_elm_present(struct omap_nand_info *info,
}
/* ELM module available, now configure it */
info->elm_dev = &pdev->dev;
if (elm_config(info->elm_dev, bch_type))
return -ENODEV;
return 0;
err = elm_config(info->elm_dev, bch_type,
(info->mtd.writesize / ecc->size), ecc->size, ecc->bytes);
return err;
}
#endif /* CONFIG_MTD_NAND_ECC_BCH */

3
include/linux/platform_data/elm.h
View File

@ -50,5 +50,6 @@ struct elm_errorvec {
void elm_decode_bch_error_page(struct device *dev, u8 *ecc_calc,
struct elm_errorvec *err_vec);
int elm_config(struct device *dev, enum bch_ecc bch_type);
int elm_config(struct device *dev, enum bch_ecc bch_type,
int ecc_steps, int ecc_step_size, int ecc_syndrome_size);
#endif /* __ELM_H */