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SubjectRe: [PATCH v5 12/15] spi: dw: Add support for AMD Pensando Elba SoC
On Mon, Jun 13, 2022 at 9:57 PM Brad Larson <brad@pensando.io> wrote:
>
> From: Brad Larson <blarson@amd.com>
>
> The AMD Pensando Elba SoC includes a DW apb_ssi v4 controller
> with device specific chip-select control. The Elba SoC
> provides four chip-selects where the native DW IP supports
> two chip-selects. The Elba DW_SPI instance has two native
> CS signals that are always overridden.

...

> +/*
> + * Elba SoC does not use ssi, pin override is used for cs 0,1 and
> + * gpios for cs 2,3 as defined in the device tree.
> + *
> + * cs: | 1 0
> + * bit: |---3-------2-------1-------0
> + * | cs1 cs1_ovr cs0 cs0_ovr
> + */

> +#define ELBA_SPICS_SHIFT(cs) (2 * (cs))

Useless.It takes much more than simply multiplying each time in two
macros. Also see below.

> +#define ELBA_SPICS_MASK(cs) (0x3 << ELBA_SPICS_SHIFT(cs))

(GENMASK(1, 0) << ((cs) << 1))

Or ((cs) * 2) to show that it takes 2 bits and not two times of CS',

> +#define ELBA_SPICS_SET(cs, val) \
> + ((((val) << 1) | 0x1) << ELBA_SPICS_SHIFT(cs))

BIT(0)

So the main point is to use GENMASK() and BIT() the rest is up to you.

--
With Best Regards,
Andy Shevchenko

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