Re: [PATCH 1/2] mtd: spi-nor: fix GigaDevice quad_enable

[Roman Yeryomin <roman@advem.lv>]

On 2019-07-28 09:21, Tudor.Ambarus@microchip.com wrote:
> On 07/28/2019 08:48 AM, Tudor.Ambarus@microchip.com wrote:
>> External E-Mail
>> 
>> 
>> Hi, Roman,
>> 
>> On 07/27/2019 12:08 AM, Roman Yeryomin wrote:
>>> External E-Mail
>>> 
>>> 
>>> According to datasheets all GD devices are capable of quad mode, 
>>> which
>> 
>> Does any of these flashes implement the Basic Flash Parameter Table? 
>> Can't we
>> determine the QE Requirements by parsing BFPT?
> 
> GD25Q256D can retrieve the QE requirements from BFPT dword 15. No need 
> to set
> the quad_enable pointer when declaring this flash, it will be 
> overwritten when
> parsing BFPT.

ok, I see, thanks for the pointer, didn't see that

> GD25Q256C implements JESD216A - just the first 9 dwords of BFPT, and it 
> can't
> determine the QE Requirements by parsing the BFPT. That's way we 
> explicitly set
> the quad_enable function pointer at flash declaration.
> 
>> 
>>> is enabled via Status Register-2, bit 1 (S9). This corresponds to
>>> Spansion SR/CR operations. Unfortunately only gd25q256 datasheet is
>>> clear about Quad Enable Requirements (QER), others have no such
>>> information in datasheets.
>>> So define quad_enable for all GD devices to be sure.
>> 
>> Which flash did you test?
> 
> What you can do is to check which of these flashes can't determine the 
> QE
> requirements by parsing BFPT and set the quad_enable just for those who 
> can't.
> And it would be preferable to do this just for the flashes that you can 
> test.

Unfortunately I don't have the devices. I only studied the datasheets.
Though I do have gd25q512 (the second patch) somewhere. I used it on one 
of embedded board prototypes.
I will try to find it and test the BFPT parsing.

>> 
>> Cheers,
>> ta
>> 
>>> Also gd25q256 is an exception. There are two versions: C and D.
>>> First one uses S6 bit (like described in e27072851bf7d) but the 
>>> latter
>>> uses S9 bit like others. To add support for D this should be handled
>>> differently, so, to retain compatibility, leave gd25q256 quad_enable
>>> callback intact.
>>> 
>>> Signed-off-by: Roman Yeryomin <roman@advem.lv>
>>> ---
>>>  drivers/mtd/spi-nor/spi-nor.c | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>> 
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>> 
>> 

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