mtd: brcmnand: Detect sticky ucorr ecc error on dma reads

This change provides a fix for controller bug where nand
controller could have a possible sticky error after a PIO
followed by a DMA read. The fix retries a read if we see
a uncorr_ecc after read to detect such sticky errors.
The fix applies to only controller version 7.0 and 7.1.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

diff --git a/drivers/mtd/nand/brcmnand/brcmnand.c b/drivers/mtd/nand/brcmnand/brcmnand.c
index f0b067229f7f5f190e28563945de91a19860c297..faca01d6e0f92a7fdd020915c9afd3f45a711e77 100644 (file)
--- a/drivers/mtd/nand/brcmnand/brcmnand.c
+++ b/drivers/mtd/nand/brcmnand/brcmnand.c
@@ -1659,9 +1659,11 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
        struct brcmnand_controller *ctrl = host->ctrl;
        u64 err_addr = 0;
        int err;
+       bool retry = true;
 
        dev_dbg(ctrl->dev, "read %llx -> %p\n", (unsigned long long)addr, buf);
 
+try_dmaread:
        brcmnand_write_reg(ctrl, BRCMNAND_UNCORR_COUNT, 0);
 
        if (has_flash_dma(ctrl) && !oob && flash_dma_buf_ok(buf)) {
@@ -1682,6 +1684,22 @@ static int brcmnand_read(struct mtd_info *mtd, struct nand_chip *chip,
        }
 
        if (mtd_is_eccerr(err)) {
+               /*
+                * On controller version and 7.0, 7.1 , DMA read after a
+                * prior PIO read that reported uncorrectable error,
+                * the DMA engine captures this error following DMA read
+                * cleared only on subsequent DMA read, so just retry once
+                * to clear a possible false error reported for current DMA
+                * read
+                */
+               if ((ctrl->nand_version == 0x0700) ||
+                   (ctrl->nand_version == 0x0701)) {
+                       if (retry) {
+                               retry = false;
+                               goto try_dmaread;
+                       }
+               }
+
                /*
                 * Controller version 7.2 has hw encoder to detect erased page
                 * bitflips, apply sw verification for older controllers only