[PATCH v5 04/10] mtd: spi-nor-core: Add support for volatile QE bit

[Jagan Teki]

On Fri, Feb 19, 2021 at 7:26 AM <tkuw584924 at gmail.com> wrote:
>
> From: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
>
> Some of Spansion/Cypress chips support volatile version of configuration
> registers and it is recommended to update volatile registers in the field
> application due to a risk of the non-volatile registers corruption by
> power interrupt. This patch adds a function to set Quad Enable bit in CFR1
> volatile.
>
> Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
> ---
> Changes in v5:
>   - Fix register address calculation, 'base | offset' -> 'base + offset'
>
>  drivers/mtd/spi/spi-nor-core.c | 53 ++++++++++++++++++++++++++++++++++
>  include/linux/mtd/spi-nor.h    |  1 +
>  2 files changed, 54 insertions(+)
>
> diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
> index 2803536ed5..87c9fce408 100644
> --- a/drivers/mtd/spi/spi-nor-core.c
> +++ b/drivers/mtd/spi/spi-nor-core.c
> @@ -1576,6 +1576,59 @@ static int spansion_read_cr_quad_enable(struct spi_nor *nor)
>         return 0;
>  }
>
> +/**
> + * spansion_quad_enable_volatile() - enable Quad I/O mode in volatile register.
> + * @nor:       pointer to a 'struct spi_nor'
> + * @addr_base: base address of register (can be >0 in multi-die parts)
> + * @dummy:     number of dummy cycles for register read
> + *
> + * It is recommended to update volatile registers in the field application due
> + * to a risk of the non-volatile registers corruption by power interrupt. This
> + * function sets Quad Enable bit in CFR1 volatile.
> + *
> + * Return: 0 on success, -errno otherwise.
> + */
> +static int spansion_quad_enable_volatile(struct spi_nor *nor, u32 addr_base,
> +                                        u8 dummy)
> +{
> +       u32 addr = addr_base + SPINOR_REG_ADDR_CFR1V;
> +
> +       u8 cr;
> +       int ret;
> +
> +       /* Check current Quad Enable bit value. */
> +       ret = spansion_read_any_reg(nor, addr, dummy, &cr);

What if we can use the exiting quad_enable hook by identifying
volatile QE at the function beginning instead of having a separate
call?

Jagan.