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

[Vignesh R]

On 07/12/18 12:47 AM, Simon Goldschmidt wrote:
> Am 06.12.2018 um 18:39 schrieb Vignesh R:
>> On 06/12/18 10:06 PM, Simon Goldschmidt wrote:
>>> Am 06.12.2018 um 14:54 schrieb Simon Goldschmidt:
>>>> On Thu, Dec 6, 2018 at 2:45 PM Vignesh R <vigneshr at ti.com> wrote:
>>>>> 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:
>>>>> [...]
[...]
>>> Had a quick test with both standard and tiny in SPL and both configs now
>>> work on my board. I haven't tested SFDP as you said it does not works on
>>> Cadence QSPI. (I tested compiling it though, and that works now.)
>>>
> 
> After enabling DEBUG in spi-mem.c, I see that we're changing to 4-byte 
> mode (via b7h) instead of using 4-byte opcodes. Unfortunately, this 
> conflicts with the boot rom using the default read opcose in 3-byte mode 
> on warm reboot.
> 
> Do you plan to change this or would this be fixed by parsing SFDP?
> 

Oh, I see n25q256a entry is missing SPI_NOR_4B_OPCODES flag in the
spi_nor_ids table. In non SFDP configuration adding SPI_NOR_4B_OPCODES
flag should avoid sending 0xb7 and use 4-byte opcodes directly. May be
you could give that a try?

>>
>> I used below hack to test SFDP with Cadence QSPI:
> 
> Just by accident, I saw that enabling the SFDP config does not seem to 
> break booting. But it still switches to 4-byte mode, so it probably just 
> fails to parse and continues the non-SFDP way?
> 

For stateless 4-byte addressing mode with SFDP, we need to parse JEDEC
4-byte Address Instruction Parameter Header and Table (part of JESD216B)
to get 4 byte addressing opcode.
We need to port this patch once accepted to Linux kernel:
https://lore.kernel.org/patchwork/patch/1022200/

>>
>> diff --git a/drivers/spi/cadence_qspi_apb.c b/drivers/spi/cadence_qspi_apb.c
>> index a8af35203035..9dbf9aa7d20c 100644
>> --- a/drivers/spi/cadence_qspi_apb.c
>> +++ b/drivers/spi/cadence_qspi_apb.c
>> @@ -559,7 +559,7 @@ int cadence_qspi_apb_indirect_read_setup(struct cadence_spi_platdata *plat,
>>          /* Configure the opcode */
>>          rd_reg = cmdbuf[0] << CQSPI_REG_RD_INSTR_OPCODE_LSB;
>>   
>> -       if (rx_width & SPI_RX_QUAD)
>> +       if (rx_width & SPI_RX_QUAD && (cmdbuf[0] != 0x5a))
> 
> But this is Spansion-specific, right?
> 

Nope, SFDP command operates in 1-1-1 mode for all flash devices. But if
you don't have rx width set to 4 in DT, above hack is not needed and
SFDP parsing would work fine with Cadence QSPI.


-- 
Regards
Vignesh