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: Pekon Gupta <pekon@ti.com>
Reviewed-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/mtd/devices/elm.c b/drivers/mtd/devices/elm.c
index f160d2c6cd59..c51752ad072e 100644
--- a/drivers/mtd/devices/elm.c
+++ b/drivers/mtd/devices/elm.c
@@ -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);