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

[Łukasz Majewski]

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?

The problem is with not clearing bit BA24 after each operation. This 
causes hangs after "reset" command.


> 
> thanks!
> 


-- 
Best regards,

Lukasz Majewski

--

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