[PATCH 1/6] spi: support simultaneous assertion of multiple CS

[Jonathan Santos]

Some SPI controllers allow multiple CS lines to be toggled at the same
time. The existing code always used CS index 0 when tracking the last
active CS in spi_set_cs(), and unconditionally set cs_index_mask to
BIT(0) when parsing DT, both forcing the single CS usage.

Modify spi_set_cs() to iterate last_cs[] using each logical CS index
instead of always reading index 0. Modify of_spi_parse_dt() to build
cs_index_mask from all parsed CS entries rather than hardcoding BIT(0),
so the controller correctly identifies which CS lines belong to a device
when asserting them simultaneously.

Signed-off-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx>
---
 drivers/spi/spi.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index d9e6b4b87c89..55fb96fea243 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1090,7 +1090,7 @@ static void spi_set_cs(struct spi_device *spi, bool enable, bool force)
 	spi->controller->last_cs_index_mask = spi->cs_index_mask;
 	for (idx = 0; idx < SPI_DEVICE_CS_CNT_MAX; idx++) {
 		if (enable && idx < spi->num_chipselect)
-			spi->controller->last_cs[idx] = spi_get_chipselect(spi, 0);
+			spi->controller->last_cs[idx] = spi_get_chipselect(spi, idx);
 		else
 			spi->controller->last_cs[idx] = SPI_INVALID_CS;
 	}
@@ -2594,10 +2594,11 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
 		spi_set_chipselect(spi, idx, cs[idx]);
 
 	/*
-	 * By default spi->chip_select[0] will hold the physical CS number,
-	 * so set bit 0 in spi->cs_index_mask.
+	 * Set cs_index_mask to indicate which logical CS indices are active.
+	 * Each bit corresponds to a logical CS index in the spi->chip_select array.
 	 */
-	spi->cs_index_mask = BIT(0);
+	for (idx = 0; idx < rc; idx++)
+		spi->cs_index_mask |= BIT(idx);
 
 	/* Device speed */
 	if (!of_property_read_u32(nc, "spi-max-frequency", &value))
-- 
2.34.1