[U-Boot] [PATCH v2] sf: bar: Clean BA24 Bank Address Register bit after read/write/erase operation

[Łukasz Majewski]

Hi Jagan,

> On Tue, Sep 26, 2017 at 12:37 PM, Łukasz Majewski <lukma at denx.de> wrote:
>> On 09/26/2017 07:40 AM, Jagan Teki wrote:
>>>
>>> On Mon, Sep 25, 2017 at 4:10 PM, Lukasz Majewski <lukma at denx.de> wrote:
>>>>
>>>> The content of Bank Address Register (BAR) is volatile. It is cleared
>>>> after power cycle or reset command (RESET F0h).
>>>>
>>>> Some memories (like e.g. s25fl256s) use it to access memory larger than
>>>> 0x1000000 (16 MiB).
>>>>
>>>> The problem shows up when one:
>>>>
>>>> 1. Reads/writes/erases memory > 16 MiB
>>>> 2. Calls "reset" u-boot command (which is not causing BAR to be cleared)
>>>>
>>>> In the above scenario, the SoC ROM sends 0x000000 address to read SPL.
>>>> Unfortunately, the BA24 bit is still set and hence it receives content
>>>> from 0x1000000 (16 MiB) memory address.
>>>> As a result the SoC aborts and we hang. Only power cycle can take the
>>>> SoC out of this state.
>>>>
>>>> How to reproduce/test:
>>>>
>>>> sf probe; sf erase 0x1200000 0x800000; reset
>>>> sf probe; sf erase 0x1200000 0x800000; sf write 0x11000000 0x1200000
>>>> 0x800000; reset
>>>> sf probe; sf read 0x11000000 0x1200000 0x800000; reset
>>>
>>>
>>> Sorry, I didn't follow this test.. are you writing on at 18MiB offset
>>> and doing reset how it will reproduce?
>>
>>
>> Please start with erase test case first.
>>
>> The problem shows up when you try to access SPI-NOR memory > 16 MiB.
>> It works with current code, since BAR is adjusted properly.
>>
>> Then after this access (without removing power), please type 'reset'
>> command.
>>
>> You will observe, that the board will not boot (if SPI-NOR is a booting
>> device).
>>
>> The problem is that ROM bootloader tries to access 0x0 address, but BA24 (in
>> the SPI-NOR controller)  is programmed from last operation (to 0x1). Hence,
>> the ROM Boot reads from 0x1000000 address.
>>
>>
>>> because we can write it 0x0 and
>>> after reset the ROM look for 16MiB on this flash this is what you
>>> concern about right?
> 
> Yes, I understand ROM look at 16MiB, but the test-case you have erase
> is from 18MiB right, it should be 0x0 on the test case right?

No it is correct.

The value 0x12000000 must only be > 16 MiB. After accessing this 
location, the BA24 bit is set.

Then after "reset" the BA24 is still set and hence BOOT ROM reads from 
wrong address.

> 
> thanks!
> 


-- 
Best regards,

Lukasz Majewski

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