Hi Frieder,
On 18.09.19 09:08, Schrempf Frieder wrote:
<snip>
One further update on this QSPI driver. This driver only works when
loaded via "imx_usb" on the i.MX6ULL EVK. When programmed into QSPI
and booted from QSPI this driver does not detect the SPI NOR
flash:
=> sf probe
unrecognized JEDEC id bytes: ff, ff, ff
Do you have any idea what might explain this difference. I would have
expected that when booting via QSPI it would be "easier" for the
driver, as the BootROM already initializes the QSPI interface. Which
is not the case in the boot via serial download (imx_usb) mode. Here
everyhting (pinmux, clocks, etc) need to be configured.
My feeling is that something is configured "incorrectly" by the
BootROM in this case which is not re-configured as the QSPI driver
needs it to be currently.
Do you have any ideas on what might be the problem here? Is there
something that I can do to help test this? Would it help if I would
send the debug logging of the driver?
I have a strong suspicion of what goes wrong in your case. We
experienced exactly the same issue recently on i.MX6ULL. For some
reasons (I guess differences in BootROM) this does not happen on i.MX6UL.
The problem is, that the BootROM sets the TDH bits in the QuadSPI_FLSHCR
register to '01' in case it uses the DDR mode. Afterwards when U-Boot or
Linux try to access the flash in SDR mode, they fail as the TDH bits are
still set. Resetting them to '00' solves the problem.
Unfortunately the TDH bits are not documented in the manual of the
i.MX6UL/ULL, but they can be found in the manual of the i.MX7.
For the QSPI driver, this means it needs a fix to set/reset the TDH bits
according to the mode that is used (DDR/SDR).
For more details please also look here:
https://community.nxp.com/thread/507260
Perfect. With these bits set to 00 again, booting from QSPI now
works on the EVK. Many thanks for this hint! :)
BTW: When receiving your mail I was just comparing the registers
settings and wondering about this difference in bit 16 as well. ;)
Thanks,
Stefan
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