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

[Jagan Teki]

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);
> +       }

It doesn't make sense to have one(specific) controller fix to be
generic to all macronix chips, think about alternative.

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