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Subject[PATCH] mtd: nand: raw: atmel: add module param to avoid using dma
Date
On a sama5d31 with a Full-HD dual LVDS panel (132MHz pixel clock) NAND
flash accesses have a tendency to cause display disturbances. Add a
module param to disable DMA from the NAND controller, since that fixes
the display problem for me.

Signed-off-by: Peter Rosin <peda@axentia.se>
---
drivers/mtd/nand/raw/atmel/nand-controller.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
index b2f00b398490..2ff7a77c7b8e 100644
--- a/drivers/mtd/nand/raw/atmel/nand-controller.c
+++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
@@ -129,6 +129,11 @@
#define DEFAULT_TIMEOUT_MS 1000
#define MIN_DMA_LEN 128

+static bool atmel_nand_avoid_dma __read_mostly;
+
+MODULE_PARM_DESC(avoiddma, "Avoid using DMA");
+module_param_named(avoiddma, atmel_nand_avoid_dma, bool, 0400);
+
enum atmel_nand_rb_type {
ATMEL_NAND_NO_RB,
ATMEL_NAND_NATIVE_RB,
@@ -1977,7 +1982,7 @@ static int atmel_nand_controller_init(struct atmel_nand_controller *nc,
return ret;
}

- if (nc->caps->has_dma) {
+ if (nc->caps->has_dma && !atmel_nand_avoid_dma) {
dma_cap_mask_t mask;

dma_cap_zero(mask);
--
2.11.0
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