Commit 3f4eb14b authored by Pekon Gupta's avatar Pekon Gupta Committed by Brian Norris
Browse files

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



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: default avatarPekon Gupta <pekon@ti.com>
Reviewed-by: default avatarEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: default avatarBrian Norris <computersforpeace@gmail.com>
parent d9ba46d3

drivers/mtd/devices/elm.c

+12 −1
Original line number Diff line number Diff line
@@ -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);

drivers/mtd/nand/omap2.c

+6 −3
Original line number Diff line number Diff line
@@ -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 */

include/linux/platform_data/elm.h

+2 −1
Original line number Diff line number Diff line
@@ -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 */

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