Messages in this thread |  | | Date | Mon, 2 Apr 2018 22:20:20 +0200 | From | Boris Brezillon <> | Subject | Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma |
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On Mon, 2 Apr 2018 21:28:43 +0200 Boris Brezillon <boris.brezillon@bootlin.com> wrote:
> On Mon, 2 Apr 2018 19:59:39 +0200 > Peter Rosin <peda@axentia.se> wrote: > > > On 2018-04-02 14:22, Boris Brezillon wrote: > > > 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). > > > > Bits 1 through 7 do not matter, so even though not equal they are (or > > should be) equivalent. But I did use 0x4d415400. I simply used the > > shorter syntax since that was easier to type and conveyed the relevant > > info. > > Ok. > > > > > >> 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? > > > > No, but did it again and checked, see transcript below. > > I don't use devmem2. Is 'readback' information accurate or is it > always what's been written? Because when you write 0x33 to 0xFFFFECBC, > 0x33 is read back, but just after that, when you read it again it's 0. > > > BTW, how do I > > know which master is in use for the LCD controller? 8 or 9? Both? > > It's configurable on a per-layer basis through the SIF bit in > LCDC_<layer>CFG0. The driver tries to dispatch the load on those 2 AHB > masters [1]. > > > And > > which DDR slave is the target? 7, 8, 9 or 10? More than one? > > This, I don't know. I guess all of them can be used.
Looks like I was wrong. According to "Table 15-3. SAMA5D3 Master to Slave Access", LCDC port 0 can only access DDR port 2 and LCDC port 1 can only access DDR port 3.
Can you try to write 0x3 to 0xFFFFECCC and 0x30 to 0xFFFFECD4?
> > > > > Cheers, > > Peter > > > > # devmem2 0xffffede4 w > > /dev/mem opened. > > Memory mapped at address 0xb6f50000. > > Value at address 0xFFFFEDE4 (0xb6f50de4): 0x0 > > # devmem2 0xffffede4 w 0x4d415401 > > /dev/mem opened. > > Memory mapped at address 0xb6f0d000. > > Value at address 0xFFFFEDE4 (0xb6f0dde4): 0x0 > > Written 0x4D415401; readback 0x4D415401 > > # devmem2 0xffffede4 w > > /dev/mem opened. > > Memory mapped at address 0xb6f55000. > > Value at address 0xFFFFEDE4 (0xb6f55de4): 0x1 > > # devmem2 0xffffede4 w 0x4d415400 > > /dev/mem opened. > > Memory mapped at address 0xb6fb5000. > > Value at address 0xFFFFEDE4 (0xb6fb5de4): 0x1 > > Written 0x4D415400; readback 0x4D415400 > > # devmem2 0xffffede4 w > > /dev/mem opened. > > Memory mapped at address 0xb6fef000. > > Value at address 0xFFFFEDE4 (0xb6fefde4): 0x0 > > > > > > # devmem2 0xffffede8 w > > /dev/mem opened. > > Memory mapped at address 0xb6fe9000. > > Value at address 0xFFFFEDE8 (0xb6fe9de8): 0x0 > > > > > > # devmem2 0xffffecbc w > > /dev/mem opened. > > Memory mapped at address 0xb6ff0000. > > Value at address 0xFFFFECBC (0xb6ff0cbc): 0x0 > > # devmem2 0xffffecbc w 0x33 > > /dev/mem opened. > > Memory mapped at address 0xb6f79000. > > Value at address 0xFFFFECBC (0xb6f79cbc): 0x0 > > Written 0x33; readback 0x33 > > # devmem2 0xffffecbc w > > /dev/mem opened. > > Memory mapped at address 0xb6efe000. > > Value at address 0xFFFFECBC (0xb6efecbc): 0x0 > > > > > > # devmem2 0xffffede8 w > > /dev/mem opened. > > Memory mapped at address 0xb6f9e000. > > Value at address 0xFFFFEDE8 (0xb6f9ede8): 0x0 > > > > [1]https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c#L498 >
-- Boris Brezillon, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com
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