Re: GPMI iMX6ull timeout on DMA

Michael Nazzareno Trimarchi
2019-07-29T12:49:54Z

Hi Miguel

On Mon, Jul 29, 2019 at 2:47 PM Miquel Raynal <miquel.raynal@bootlin.com> wrote:
>
> Hi Greg,
>
> + Boris
>
> Greg Ungerer <gerg@kernel.org> wrote on Mon, 29 Jul 2019 22:33:56 +1000:
>
> > Hi Miquel,
> >
> > On 29/7/19 6:36 pm, Miquel Raynal wrote:
> > > Hi Greg,
> > >
> > > One question below.
> > >
> > > +Michael
> > > +Sascha
> > >
> > > Hello Michael, here is a similar issue to yours, I know you did not
> > > have enough time to share your solution but here we have someone else
> > > reproducing the issue, would you mind sharing a branch or a patch, even
> > > a WIP one, just to help debugging?
> > >
> > > Greg Ungerer <gerg@kernel.org> wrote on Mon, 29 Jul 2019 16:41:51 +1000:
> > >
> > >> Hi Miquel,
> > >>
> > >> I am experiencing a problem with NAND flash DMA timeouts on
> > >> iMX6ull based boards. The problem is very similar to that
> > >> described in:
> > >>
> > >> https://linux-mtd.infradead.narkive.com/JIUulfFB/gpmi-imx6ull-timeout-on-dma
> > >>
> > >> That didn't come to any specific resolution that I could see
> > >> in that thread.
> > >>
> > >> The boot trace on the console for me looks like this:
> > >>
> > >> nand: device found, Manufacturer ID: 0x2c, Chip ID: 0xda
> > >> nand: Micron MT29F2G08ABAEAWP
> > >> nand: 256 MiB, SLC, erase size: 128 KiB, page size: 2048, OOB size: 64
> > >> gpmi-nand 1806000.gpmi-nand: DMA timeout, last DMA
> > >> gpmi-nand 1806000.gpmi-nand: Show GPMI registers :
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x000 : 0x20830002
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x010 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x020 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x030 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x040 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x050 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x060 : 0x01c6800c
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x070 : 0x00010101
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x080 : 0xe0000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x090 : 0x23023336
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0a0 : 0x000001ee
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0b0 : 0xff000001
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0c0 : 0x00000001
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0d0 : 0x05020000
> > >> gpmi-nand 1806000.gpmi-nand: Show BCH registers :
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x000 : 0x00000100
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x010 : 0x00000010
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x020 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x030 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x040 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x050 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x060 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x070 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x080 : 0x030a2080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x090 : 0x083e2080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0a0 : 0x070a4080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0b0 : 0x10da4080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0c0 : 0x070a4080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0d0 : 0x10da4080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0e0 : 0x070a4080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x0f0 : 0x10da4080
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x100 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x110 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x120 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x130 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x140 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x150 : 0x20484342
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x160 : 0x01000000
> > >> gpmi-nand 1806000.gpmi-nand: offset 0x170 : 0x00000000
> > >> gpmi-nand 1806000.gpmi-nand: BCH Geometry :
> > >> GF length : 13
> > >> ECC Strength : 8
> > >> Page Size in Bytes : 2110
> > >> Metadata Size in Bytes : 10
> > >> ECC Chunk0 Size in Bytes: 512
> > >> ECC Chunkn Size in Bytes: 512
> > >> ECC Chunk Count : 4
> > >> Payload Size in Bytes : 2048
> > >> Auxiliary Size in Bytes: 16
> > >> Auxiliary Status Offset: 12
> > >> Block Mark Byte Offset : 1999
> > >> Block Mark Bit Offset : 0
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -110
> > >> nand: timing mode 5 not acknowledged by the NAND chip
> > >
> > > What is the final timing mode used? Most of us tested in mode 5 I
> > > guess, maybe mode 4 is broken (don't know if this is the one used here,
> > > neither why mode 5 is refused). Can you please try by limiting the mode
> > > to 0, 1, 2... until, hopefully, we narrow down to the failing mode.
> >
> > Sure, how to do that?
>
> This loop [1] tries to configure each mode (5, 4, ...) until one
> succeeds (default is 0: must always work). Please try to limit mode to
> 0, 1, etc.
>
> Mode 0 should work.
>

This is not correct. When all the mode fail it fallback to 0 that does
not work. Already check
So the fallback is created for this situation

> [1] https://elixir.bootlin.com/linux/v5.3-rc1/source/drivers/mtd/nand/raw/nand_base.c#L933
>
> >
> >
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> Scanning device for bad blocks
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> ....
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> gpmi-nand 1806000.gpmi-nand: Chip: 0, Error -22
> > >> 5 fixed-partitions partitions found on MTD device gpmi-nand
> > >> Creating 5 MTD partitions on "gpmi-nand":
> > >> 0x000000000000-0x000000500000 : "u-boot"
> > >> 0x000000500000-0x000000600000 : "u-boot-env"
> > >> 0x000000600000-0x000000800000 : "log"
> > >> 0x000000800000-0x000010000000 : "flash"
> > >> 0x000000000000-0x000010000000 : "all"
> > >> gpmi-nand 1806000.gpmi-nand: driver registered.
> > >>
> > >>
> > >> This is using a linux kernel v5.1.14. I have seen this happen on
> > >> a number of boards I have here - but it is only occasional. It
> > >> only happens once in a while on boot, maybe 1 in 40 or more times.
> > >> So it can take quite a while to reproduce (using a boot loop setup).
> > >
> > > That's strange... I don't get what would produce such unstable issue.
> >
> > My initial guess is that the calculated timing is very marginal.
>
> What do you mean by "marginal"?
>

I don't think that is timing calculation. I have tried to use the same timing
as before but when those are applide. Is it possible?

Michael

> > The problem seems more likely to happen if flash write activity
> > had been occurring just before a soft reboot. Its not a guarantee,
> > just more likely.
>
> That's really disturbing. I doubt this is the real cause though.
>
> >
> > Interesting observation is that Michael was using Micron flash,
> > and boards that I have with the problem also have Micron flash.
> > Both a form of Micron MT29F2G08.
> >
> > I have similar boards, iMX6ull based, with different brands of
> > NAND flash and I have not seen any problem on them.
>
> That's great to narrow down the root cause. Maybe these chips have
> tighter timing constraints.
>
> >
> > Regards
> > Greg
> >
> >
> >
> > >> As per the email thread I pointed to above I looked at reverting
> > >> those patches, but that was not at all easy given how much the gpmi
> > >> driver code had moved. So instead I modified the code with this:
> > >>
> > >> --- a/linux/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> > >> +++ b/linux/drivers/mtd/nand/raw/gpmi-nand/gpmi-lib.c
> > >> @@ -481,6 +481,7 @@ static void gpmi_nfc_compute_timings(struct gpmi_nand_data *this,
> > >> void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
> > >> {
> > >> +#if 0
> > >> struct gpmi_nfc_hardware_timing *hw = &this->hw;
> > >> struct resources *r = &this->resources;
> > >> void __iomem *gpmi_regs = r->gpmi_regs;
> > >> @@ -505,6 +512,7 @@ void gpmi_nfc_apply_timings(struct gpmi_nand_data *this)
> > >> /* Wait for the DLL to settle. */
> > >> udelay(dll_wait_time_us);
> > >> +#endif
> > >> }
> > >> int gpmi_setup_data_interface(struct nand_chip *chip, int chipnr,
> > >>
> > >> So far after a couple of days of testing with this I no longer
> > >> see the DMA timeout.
> > >>
> > >> Any thoughts?
> > >>
> > >> Regards
> > >> Greg
> > >>
> > >
> > > Thanks,
> > > Miquèl
> > >
>
> Thanks,
> Miquèl

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