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

[Łukasz Majewski]

Hi Jagan,

> On Wed, Sep 13, 2017 at 3:09 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 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
>>
>> Signed-off-by: Lukasz Majewski <lukma at denx.de>
>> ---
>>   drivers/mtd/spi/spi_flash.c | 33 +++++++++++++++++++++++++++++++++
>>   1 file changed, 33 insertions(+)
>>
>> diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
>> index 34f6888..d19d64a 100644
>> --- a/drivers/mtd/spi/spi_flash.c
>> +++ b/drivers/mtd/spi/spi_flash.c
>> @@ -113,6 +113,27 @@ static int write_cr(struct spi_flash *flash, u8 wc)
>>   #endif
>>
>>   #ifdef CONFIG_SPI_FLASH_BAR
>> +/*
>> + * This "cleanup" is necessary in a situation when one was accessing
>> + * spi flash memory > 16 MiB by using Bank Address Register's BA24 bit.
>> + *
>> + * After it the BA24 bit shall be cleared to allow access to correct
>> + * memory region after SW reset (by calling "reset" command).
>> + *
>> + * Otherwise, the BA24 bit may be left set and then after reset, the
>> + * ROM would seek for SPL from 0x1000000, not 0x0.
> 
> This need to change, SPL will look 16 MiB * bank_sel

Ok. I will update the description.

> 
>> + */
>> +static int cleanup_bar(struct spi_flash *flash)
> 
> what about clear_bar?

Ok. I will change the name.

> 
> thanks!
> 


-- 
Best regards,

Lukasz Majewski

--

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