Messages in this thread |  | | Date | Mon, 2 Apr 2018 14:22:49 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma |
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On Thu, 29 Mar 2018 16:27:12 +0200 Peter Rosin <peda@axentia.se> wrote:
> On 2018-03-29 15:44, Boris Brezillon wrote: > > On Thu, 29 Mar 2018 15:37:43 +0200 > > Peter Rosin <peda@axentia.se> wrote: > > > >> On 2018-03-29 15:33, Boris Brezillon wrote: > >>> On Thu, 29 Mar 2018 15:10:54 +0200 > >>> Peter Rosin <peda@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 <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); > >>> > >>> 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.
You mean 0x4D415400, right? ("MAT0" != 0x4D415400).
> But when I try to write to "Priority Registers B For Slaves" it doesn't > take, regardless of write protect mode.
Did you check MATRIX_WPSR after writing to MATRIX_PRXSY?
> > Can the relevant bits only be written when the HLCDC is inactive or > something?
I don't know, but maybe Nicolas does.
-- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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