[U-Boot] [PATCH 2/2] sf: Preserve QE bit when clearing BP# bits for Macronix flash

[Bin Meng]

Hi Jagan,

On Wed, Aug 16, 2017 at 6:34 PM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
> Hi Bin,
>
> On Wed, Aug 16, 2017 at 7:29 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Hi Jagan,
>>
>> On Mon, Aug 14, 2017 at 1:35 PM, Bin Meng <bmeng.cn at gmail.com> wrote:
>>> Hi Jagan,
>>>
>>> On Mon, Aug 14, 2017 at 1:17 PM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>> On Mon, Aug 14, 2017 at 10:34 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>> Hi Jagan,
>>>>>
>>>>> On Mon, Aug 14, 2017 at 12:58 PM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>> Hi Bin,
>>>>>>
>>>>>> On Mon, Aug 14, 2017 at 8:07 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>>>> Hi Jagan,
>>>>>>>
>>>>>>> On Mon, Aug 14, 2017 at 1:22 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>>>> Hi Bin,
>>>>>>>>
>>>>>>>> On Wed, Aug 2, 2017 at 3:56 AM, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>>>>>> Hi Jagan,
>>>>>>>>>
>>>>>>>>> On Wed, Aug 2, 2017 at 12:01 AM, Jagan Teki <jagannadh.teki at gmail.com> wrote:
>>>>>>>>>> On Sun, Jul 23, 2017 at 8:14 PM, Bin Meng <bmeng.cn at gmail.com> wrote:
>>>>>>>>>>> On some flash (like Macronix), QE (quad enable) bit is in the same
>>>>>>>>>>> status register as BP# bits, and we need preserve its original value
>>>>>>>>>>> during a reboot cycle as this is required by some platforms (like
>>>>>>>>>>> Intel ICH SPI controller working under descriptor mode).
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>>>>>>>>>> ---
>>>>>>>>>>>
>>>>>>>>>>>  drivers/mtd/spi/spi_flash.c | 17 +++++++++++++++--
>>>>>>>>>>>  1 file changed, 15 insertions(+), 2 deletions(-)
>>>>>>>>>>>
>>>>>>>>>>> diff --git a/drivers/mtd/spi/spi_flash.c b/drivers/mtd/spi/spi_flash.c
>>>>>>>>>>> index 0034a28..7d8c660 100644
>>>>>>>>>>> --- a/drivers/mtd/spi/spi_flash.c
>>>>>>>>>>> +++ b/drivers/mtd/spi/spi_flash.c
>>>>>>>>>>> @@ -947,11 +947,24 @@ int spi_flash_scan(struct spi_flash *flash)
>>>>>>>>>>>         if (IS_ERR_OR_NULL(info))
>>>>>>>>>>>                 return -ENOENT;
>>>>>>>>>>>
>>>>>>>>>>> -       /* Flash powers up read-only, so clear BP# bits */
>>>>>>>>>>> +       /*
>>>>>>>>>>> +        * Flash powers up read-only, so clear BP# bits.
>>>>>>>>>>> +        *
>>>>>>>>>>> +        * Note on some flash (like Macronix), QE (quad enable) bit is in the
>>>>>>>>>>> +        * same status register as BP# bits, and we need preserve its original
>>>>>>>>>>> +        * value during a reboot cycle as this is required by some platforms
>>>>>>>>>>> +        * (like Intel ICH SPI controller working under descriptor mode).
>>>>>>>>>>> +        */
>>>>>>>>>>>         if (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_ATMEL ||
>>>>>>>>>>> -           JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_MACRONIX ||
>>>>>>>>>>>             JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_SST)
>>>>>>>>>>>                 write_sr(flash, 0);
>>>>>>>>>>> +       if (JEDEC_MFR(info) == SPI_FLASH_CFI_MFR_MACRONIX) {
>>>>>>>>>>> +               u8 sr = 0;
>>>>>>>>>>> +
>>>>>>>>>>> +               read_sr(flash, &sr);
>>>>>>>>>>> +               sr &= STATUS_QEB_MXIC;
>>>>>>>>>>> +               write_sr(flash, sr);
>>>>>>
>>>>>> Better assign sr with QEB for macronix and call write_sr once.
>>>>>
>>>>> For these Macronix flashes that does not support quard RW, QEB bit is
>>>>> reserved. Writing 1 to a reserved bit is not a good practice.
>>>>
>>>> Yeah, i.e what I'm concern here. (apart from fixing comment) this
>>>> issue came-up with your controller along with specific connected chip
>>>> which support RW WEB.
>>>
>>> As I said, this is nothing related to the SPI controller driver. It
>>> can (technically) happen on other platforms. I don't understand what
>>> your concerns here. Your suggestion of writing SR once does not work.
>
> OK, then lets proceed with this.
>
> finally, I've made a change for easy readability [1], If you're OK I
> will apply this otherwise suggest any?
>
> [1] https://paste.ubuntu.com/25324972/
>

Looks good. Please apply. Thanks!

Regards,
Bin