GPMI iMX6ull timeout on DMA

[Greg Ungerer <gerg@kernel.org>]

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
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).

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


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