[PATCH] mtd: nand: pxa3xx-nand: prevent DFI bus lockup on removal

[Robert Jarzmik]

After the conversion of pxa architecture to common clock framework, the
NAND clock can be disabled on driver exit.

In this case, it happens that if the driver used the NAND and set the
DFI arbitration bit, the next access to a static memory controller area,
such as an ethernet card, will stall the system bus, and the core will
be stalled forever.

This is especially true on pxa31x SoCs, where the NDCR was augmented
with a new bit to prevent this lockups by giving full ownership of the
DFI arbiter to the SMC, in change SCr#6.

Fix this by clearing the DFI arbritration bit in driver exit. This
effectively prevents a lockup on zylonite when removing pxa3xx-nand
module, and using ethernet afterwards.

Signed-off-by: Robert Jarzmik <robert.jarzmik at free.fr>

---
Ezequiel, this deserves a test on Armada, as the bit has another meaning
there I think.
---
 drivers/mtd/nand/pxa3xx_nand.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
index f287ce9e225a..087d769f92fd 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -78,6 +78,7 @@
 #define NDCR_NAND_MODE   	(0x0)
 #define NDCR_CLR_PG_CNT		(0x1 << 20)
 #define NDCR_STOP_ON_UNCOR	(0x1 << 19)
+#define NDCR_ARB_CNTL		(0x1 << 19)
 #define NDCR_RD_ID_CNT_MASK	(0x7 << 16)
 #define NDCR_RD_ID_CNT(x)	(((x) << 16) & NDCR_RD_ID_CNT_MASK)
 
@@ -1322,7 +1323,8 @@ static int pxa3xx_nand_detect_config(struct pxa3xx_nand_info *info)
 	}
 
 	/* Set an initial chunk size */
-	info->reg_ndcr = ndcr & ~NDCR_INT_MASK;
+	info->reg_ndcr = ndcr &
+		~(NDCR_INT_MASK | NDCR_ND_ARB_EN | NDCR_ARB_CNTL);
 	info->ndtr0cs0 = nand_readl(info, NDTR0CS0);
 	info->ndtr1cs0 = nand_readl(info, NDTR1CS0);
 	return 0;
@@ -1569,6 +1571,7 @@ static int pxa3xx_nand_scan(struct mtd_info *mtd)
 	pxa3xx_flash_ids[1].name = NULL;
 	def = pxa3xx_flash_ids;
 KEEP_CONFIG:
+	info->reg_ndcr |= (pdata->enable_arbiter) ? NDCR_ND_ARB_EN : 0;
 	if (info->reg_ndcr & NDCR_DWIDTH_M)
 		chip->options |= NAND_BUSWIDTH_16;
 
@@ -1784,6 +1787,8 @@ static int pxa3xx_nand_remove(struct platform_device *pdev)
 		free_irq(irq, info);
 	pxa3xx_nand_free_buff(info);
 
+	nand_writel(info, NDCR,
+		    (nand_readl(info, NDCR) & ~NDCR_ND_ARB_EN) | NDCR_ARB_CNTL);
 	clk_disable_unprepare(info->clk);
 
 	for (cs = 0; cs < pdata->num_cs; cs++)
-- 
2.1.4