On Thu, 29 Mar 2018 15:10:54 +0200 Peter Rosin <[email protected]> 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 <[email protected]> > --- > 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); I'm not a big fan of those driver specific cmdline parameters. Can't we instead give an higher priority to HLCDC master using the bus matrix? > + > 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); -- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
