[PATCH 2/2] mtd: spi-nor: Disable the flash quad mode in spi_nor_restore()

[Yicong Yang]

Hi Matthias,


On 2020/9/2 20:15, Matthias Weißer wrote:
> Hi Vignesh
>
> Am Di., 1. Sept. 2020 um 16:20 Uhr schrieb Yicong Yang
> <yangyicong at hisilicon.com>:
>> I've tested the following patch with s25fs128s1.
>> I left the flash quad enabled before managed by spi-nor driver,
>> and it'll stay QE after removed. So I think it'll also address the issue
>> mentioned. Please have a test.
> Thanks for the patch. I can confirm that current 5.9-rc3 bricks my hardware
> and your patch on top of it fixes that. Therefore
>
> Tested-by: Matthias Weisser <m.weisser.m at gmail.com>
>
> But I am still concerned about wearing out nonvolatile QE bits (not in my
> case, but there may be others) which may also brick hardware after a lot of
> boots (by set and reset QE bit on every boot).
>
> So, from my limited point of view, your patch fixes my problem but overall
> I think the original approach should be thought-out a bit more.

Thanks for testing the patch.

The driver will try to set the QE bit when 1) in ->quad_enable() if QE bit is not set and
2) previously without this patch in spi_nor_restore() to try to disable the flash quad mode.

With this patch, if the QE bit is originally set the driver will only read and record it and
will not disable the quad mode in spi_nor_restore(). What the driver will do is to read
the bit, without trying to set or reset it. So I think it will not wear out the those nonvolatile
QE bits.

Regards,
Yicong


>
> Regards,
> Matthias
> .
>