[U-Boot] [RFC PATCH v2 00/11] SF: Migrate to Linux SPI NOR framework

[Simon Goldschmidt]

On Thu, Dec 6, 2018 at 2:45 PM Vignesh R <vigneshr at ti.com> wrote:
>
> Hi Simon,
>
> On 06/12/18 2:15 AM, Simon Goldschmidt wrote:
> > Am 05.12.2018 um 07:55 schrieb Simon Goldschmidt:
> >> On Wed, Dec 5, 2018 at 7:51 AM Vignesh R <vigneshr at ti.com> wrote:
> [...]
> >>>> I did some compilation tests first and I'm happy to say that with the
> >>>> SPL_SPI_FLASH_TINY option enabled, my SPL is about 1900 byte smaller
> >>>> than before :-)
> >>>>
> >>>> However, my socfpga socrates board does not boot. I'll have to
> >>>> investigate why. I just applied this series and compiled for
> >>>> socfpga_socrates_defconfig. Is there anything else I should have changed
> >>>> to make it work?
> >>>>
> >>>
> >>> Oops, that's unfortunate.
> >>> Just to be sure, does SPL fail to come up or SPL fails to load U-Boot
> >>> from flash? Is this with SPL_SPI_FLASH_TINY enabled?
> >>
> >> I tried both TINY and standard. Both are failing to load U-Boot (I get
> >> the standard error message that loading from SPI flash failed).
> >>
> >>> Could you enable debug prints at the end of spi_mem_exec_op() in
> >>> drivers/spi/spi-mem.c to see what commands are sent and their responses?
> >>
> >> OK, I'll do that.
> >>
> >>> I have TI EVM with Cadence QSPI(like SoCFPGA) but with a Spansion flash
> >>> and that seems to work fine with both full and tiny stack.
> >
> > OK, so I enabled some debugging and the first issue is that U-Boot has
> > SNOR_MFR_MICRON and SNOR_MFR_ST while Linux only has SNOR_MFR_MICRON but
> > defines it to CFI_MFR_ST (0x20, U-Boot ends up with 0x2c). While this
> > might be correct, it leads to my n25q256a not being handled as
> > "micron-like" and the code falls through to using Spansion-like opcode
> > (0x17) that my chip does not understand.
> >
>
> Oops, sorry, the micron chip I had has CFI MFR id of 0x2c, so I
> overlooked this. I have updated this now.
>
> > However, after changing this (and using opcode 0xb7 to bring the chip
> > into 4 byte mode, including 0x06 for write-enable), it still does not
> > work as it uses the 'READ' opcode 0x03 instead of the 'FAST READ' opcode
> > 0x0b that U-Boot used until now. The problem here might be that 'READ'
> > cannot do Quad-SPI (4-4-4) and I'm not sure the Cadence driver can
> > handle Extended-SPI (1-1-1) that the 'READ' command is limited to...
> >
>
> I had accidentally dropped Fast Read from SPI NOR layer and have sync'd
> it up now.  I see that in socfpga dts, flash does not contain:
> spi-rx-bus-width = <4>;

We can add that if it helps. I'll try to update the upstream Linux dts
anyway to add "jeded,spi-nor" compatible once Neil's series is
applied.

> Therefore SPI NOR layer falls back to READ (even though its a QSPI
> flash). But nevertheless with updated branch[1] you should see falling
> back to FAST READ with Cadence QSPI on your board (and 1-1-4, if rx bus
> width is 4).
>
> > Using SFDP would probably help, but that doesn't compile (as I wrote in
> > the other thread).
> >
>
> Sorry for that. I have fixed that up and tested SFDP parsing logic with
> a Spansion flash. Note that Cadence QSPI wont support SFDP parsing as
> driver enables Quad mode for all reads and SFDP is only 1-1-1.

Oh, I haven't really looked into that yet. That's sad.

>
> > On the other hand, enabling SFDP will increase the text/rodata size for
> > SPL. We might need to remove the non-SFDP and write code as a counter
> > measure to prevent increasing code size.
> >
>
> That's not an option as Flash devices (even though have same JEDEC ID)
> manufactured before JESD216 std dont have SFDP populated. So, we will
> need to have both non-SFDP and SFDP support with option to disable SFDP
> (for size and boot time optimizations).

Well, my idea was if you'd know that all the flash chips on your board
supported it, you'd be safe. It would only be a Kconfig option to
reduce binary size (get rid of the flash IDs table).

But if SFDP doesn't work for QSPI anyway, that's not the best idea, I guess...

> Thanks for all the debugging! It would be great if you could try below
> branch and let me know if it fixes all the issues.
> If yes, I will remove RFC and post new series.

Sure, I'll try to find the time soon.

Regards,
Simon

>
> [1] https://github.com/r-vignesh/u-boot.git spi-nor-mig-patch-v1
>
> --
> Regards
> Vignesh