On Mon, Jun 13, 2022 at 9:57 PM Brad Larson [off-list ref] 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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