On 2018-03-29 16:27, Peter Rosin wrote: > On 2018-03-29 15:44, Boris Brezillon wrote: >> On Thu, 29 Mar 2018 15:37:43 +0200 >> Peter Rosin <p...@axentia.se> wrote: >> >>> On 2018-03-29 15:33, Boris Brezillon wrote: >>>> On Thu, 29 Mar 2018 15:10:54 +0200 >>>> Peter Rosin <p...@axentia.se> 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); >>>> >>>> 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? >>> >>> I don't know if it will be enough, but we sure can try. However, I have >>> no idea how to do that. I will happily test stuff though... >> >> There's no interface to configure that from Linux, but you can try to >> tweak it with devmem and if that does the trick, maybe we can expose a >> way to configure that from Linux. For more details, see the "Bus Matrix >> (MATRIX)" section in Atmel datasheets. > > I don't seem to succeed in changing the registers I think I need to change. > I can poke the "Write Protection Mode Register" by writing MAT0 and MAT1 to > it. But when I try to write to "Priority Registers B For Slaves" it doesn't > take, regardless of write protect mode. > > Can the relevant bits only be written when the HLCDC is inactive or > something?
Here is someone else with what seems like very similar problems[1], however also with USB disturbing the display. I can't test that (easily) since a mux in front of the USB port was unfortunately wired incorrectly in this first attempt. And USB disturbing the display is not a showstopper around here, since USB will only be used for debugging etc in my case. [1] https://www.avrfreaks.net/forum/sama5d31-ahb-bus-matrix-lcd Cheers, Peter