mtd: nand: pxa3xx: Support command buffer #3

Some newer controllers support a fourth command buffer. This additional
command buffer allows to set an arbitrary length count, using the
NDCB3.NDLENCNT field, to perform non-standard length operations
such as the ONFI parameter page read.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index 6e28121d3118..b3fc146cdccf 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -197,6 +197,7 @@ struct pxa3xx_nand_info {
         uint32_t                ndcb0;
         uint32_t                ndcb1;
         uint32_t                ndcb2;
+        uint32_t                ndcb3;
 };
 
 static bool use_dma = 1;
@@ -493,9 +494,22 @@ static irqreturn_t pxa3xx_nand_irq(int irq, void *devid)
                 nand_writel(info, NDSR, NDSR_WRCMDREQ);
                 status &= ~NDSR_WRCMDREQ;
                 info->state = STATE_CMD_HANDLE;
+
+                /*
+                 * Command buffer registers NDCB{0-2} (and optionally NDCB3)
+                 * must be loaded by writing directly either 12 or 16
+                 * bytes directly to NDCB0, four bytes at a time.
+                 *
+                 * Direct write access to NDCB1, NDCB2 and NDCB3 is ignored
+                 * but each NDCBx register can be read.
+                 */
                 nand_writel(info, NDCB0, info->ndcb0);
                 nand_writel(info, NDCB0, info->ndcb1);
                 nand_writel(info, NDCB0, info->ndcb2);
+
+                /* NDCB3 register is available in NFCv2 (Armada 370/XP SoC) */
+                if (info->variant == PXA3XX_NAND_VARIANT_ARMADA370)
+                        nand_writel(info, NDCB0, info->ndcb3);
         }
 
         /* clear NDSR to let the controller exit the IRQ */
@@ -554,6 +568,7 @@ static int prepare_command_pool(struct pxa3xx_nand_info *info, int command,
         default:
                 info->ndcb1 = 0;
                 info->ndcb2 = 0;
+                info->ndcb3 = 0;
                 break;
         }