Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma

[Nicolas Ferre]

On 29/03/2018 at 15:10, Peter Rosin wrote:
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 <p...@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);

We had the DT parameter "atmel,nand-has-dma" for this purpose and it was 
associated with a module parameter as well (use_dma,).

Is it only managed by old DT binding?

Best regards,
  Nicoals

  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);



--
Nicolas Ferre