From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jagan Teki <jagannadh.teki@gmail.com>
Date: Wed, 16 Aug 2017 18:27:15 +0530
Subject: [U-Boot] [PATCH 2/2] sf: Preserve QE bit when clearing BP# bits
 for Macronix flash
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On Wed, Aug 16, 2017 at 5:56 PM, Bin Meng <bmeng.cn@gmail.com> wrote:
> Hi Jagan,
>
> On Wed, Aug 16, 2017 at 6:34 PM, Jagan Teki <jagannadh.teki@gmail.com> wrote:
>> Hi Bin,
>>
>> On Wed, Aug 16, 2017 at 7:29 AM, Bin Meng <bmeng.cn@gmail.com> wrote:
>>> Hi Jagan,
>>>
>>> On Mon, Aug 14, 2017 at 1:35 PM, Bin Meng <bmeng.cn@gmail.com> wrote:
>>>> Hi Jagan,
>>>>
>>>> On Mon, Aug 14, 2017 at 1:17 PM, Jagan Teki <jagannadh.teki@gmail.com> wrote:
>>>>> On Mon, Aug 14, 2017 at 10:34 AM, Bin Meng <bmeng.cn@gmail.com> wrote:
>>>>>> Hi Jagan,
>>>>>>
>>>>>> On Mon, Aug 14, 2017 at 12:58 PM, Jagan Teki <jagannadh.teki@gmail.com> wrote:
>>>>>>> Hi Bin,
>>>>>>>
>>>>>>> On Mon, Aug 14, 2017 at 8:07 AM, Bin Meng <bmeng.cn@gmail.com> wrote:
>>>>>>>> Hi Jagan,
>>>>>>>>
>>>>>>>> On Mon, Aug 14, 2017 at 1:22 AM, Jagan Teki <jagannadh.teki@gmail.com> wrote:
>>>>>>>>> Hi Bin,
>>>>>>>>>
>>>>>>>>> On Wed, Aug 2, 2017 at 3:56 AM, Bin Meng <bmeng.cn@gmail.com> wrote:
>>>>>>>>>> Hi Jagan,
>>>>>>>>>>
>>>>>>>>>> On Wed, Aug 2, 2017 at 12:01 AM, Jagan Teki <jagannadh.teki@gmail.com> wrote:
>>>>>>>>>>> On Sun, Jul 23, 2017 at 8:14 PM, Bin Meng <bmeng.cn@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@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/

Applied to u-boot-spi/master

thanks!
-- 
Jagan Teki
Free Software Engineer | www.openedev.com
U-Boot, Linux | Upstream Maintainer
Hyderabad, India.