[U-Boot] [PATCH] sf: ensure flash device is in 3-byte address mode

[Simon Goldschmidt]

Hi Jagan,

On 21.05.2018 17:09, Jagan Teki wrote:
> Hi Simon,
> 
> On Fri, May 18, 2018 at 12:48 PM, Simon Goldschmidt
> <sgoldschmidt at de.pepperl-fuchs.com> wrote:
>>
>> On 14.05.2018 09:47, Simon Goldschmidt wrote:
>>>
>>>
>>>
>>> On 14.05.2018 09:22, Jagan Teki wrote:
>>>>
>>>> On Mon, May 14, 2018 at 12:34 PM, Simon Goldschmidt
>>>> <sgoldschmidt at de.pepperl-fuchs.com> wrote:
>>>>>
>>>>> + Marek for the socfpga platform, see below
>>>>>
>>>>> On 07.12.2017 06:49, Jagan Teki wrote:
>>>>>>
>>>>>>
>>>>>> On Tue, Dec 5, 2017 at 11:50 AM, Goldschmidt Simon
>>>>>> <sgoldschmidt at de.pepperl-fuchs.com> wrote:
>>>>>>>
>>>>>>>
>>>>>>> + Lukasz (as a reviewer of my patch[1])
>>>>>>>
>>>>>>> On Mon, Dec 4, 2017 at 8:20, Jagan Teki wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> This is the patch[1] for 4-byte addressing, but I would wonder how
>>>>>>>> can
>>>>>>>> proceed
>>>>>>>> operations with 4-byte if we disable during probe.
>>>>>>>>
>>>>>>>> [1] http://git.denx.de/?p=u-boot-
>>>>>>>> spi.git;a=commitdiff;h=fd0c22a90772379c4c11ba09347d36cc8ee17dca
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> OK, so your patch does something different than what I did.
>>>>>>>
>>>>>>> I was trying to keep the change to U-Boot as small as possible, only
>>>>>>> fixing this issue I was seeing:
>>>>>>>
>>>>>>> After a soft-reboot where the SPI chip was not reset, it is left in
>>>>>>> 4-byte addressing mode (linux uses this mode, obviously). Remember
>>>>>>> that 4-byte mode is not a permanent setting, so we can enter and
>>>>>>> leave it any time we like by issuing a command.
>>>>>>>
>>>>>>> U-Boot uses the Bank Address Register (BAR) for spi flash chips with
>>>>>>> more than 16 MByte, so it impclitly assumes that the chip is in
>>>>>>> 3-byte address mode. As I see it, your patch is worth a discussion
>>>>>>> named "should we use 4-byte addressing mode on spi flash chips?".
>>>>>>> I do think this is a better alternative than writing BAR! But this
>>>>>>> change probably needs discussion and testing.
>>>>>>
>>>>>>
>>>>>>
>>>>>> OK, will review your patch.
>>>>>
>>>>>
>>>>>
>>>>> Any update here? The last input on this is about five months old! This
>>>>> is
>>>>> the last patch I need to run my socfpga board from qspi.
>>>>>
>>>>> I added Marek to the discussion as at least the SoCrates board does not
>>>>> have
>>>>> a reset connected to the qspi chip and needs this as well. Note that the
>>>>> system boot rom does not have a problem with the chip being in 4-byte
>>>>> mode
>>>>> but SPL fails to load U-Boot from qspi.
>>>>
>>>>
>>>> Does Linux do this stuff? say my flash in 4-byte and flashed SPL and
>>>> rebooted.
>>>
>>>
>>> Yes. My code is inspired by 'drivers/mtd/spi-bor/spi-nor.c' function
>>> 'set_4byte'. I'm using 4.9 where they don't have support for 4 byte opcodes
>>> (which is why I'm seeing this bug after all). OK, this is not the latest
>>> kernel, but it's LTS, so I think U-Boot should handle this Kernel.
>>>
>>> What happens in Linux (4.9) is that depending on the flash size, 4-byte
>>> mode is *always* enabled. And it stays enabled after soft reboot. So
>>> consequently, we have to *always* disable it in U-Boot.
>>>
>>> In newer versions, they still use 4-byte mode if the flash chip does not
>>> support 4-byte opcodes. I suppose that would fix it for me, too, but I'm
>>> stuck with LTS for now.
>>
>>
>> Do you need any more information here? I'd really love to get this into
>> 2018.07, finally. As I said before, this is the last patch missing for
>> socfpga cyclone5 running from qspi.
> 
> The point I'm not clear is we don't have 4-byte addressing (we are
> using Bank addressing for > 16MiB) so how come we disable 4-byte
> addressing for the sake of other software blocks enabled it? It's like
> a hack to me.

I understand your point. However, there *are* SPI chips without a reset 
line. And if linux brings them into 4-byte address mode and then the 
system gets a warm reset e.g. by the watchdog, where do you suggest to 
set the chip back to 3-byte address mode?

Simon