[PATCH v1] spi: qcom-geni: Fix cs_change handling on the last transfer

[Viken Dadhaniya]

Commit b99181cdf9fa ("spi-geni-qcom: remove manual CS control") introduced
automatic CS control via the FRAGMENTATION bit, but missed the case where
cs_change is set on the last transfer in a message.

For the last transfer, cs_change means that CS should remain asserted after
the message completes. Since GENI SPI controls CS through FRAGMENTATION,
set FRAGMENTATION for this case as well as for non-last transfers where
cs_change is not set.

Additionally, setup_gsi_xfer() was storing FRAGMENTATION (BIT(2) = 4) in
peripheral.fragmentation, which is a boolean field consumed by
gpi_create_spi_tre() via u32_encode_bits(..., TRE_SPI_GO_FRAG). Storing 4
causes u32_encode_bits to mask it to 0, silently disabling the FRAG bit in
the GPI TRE regardless of the cs_change logic. Store 1 instead.

Without these fixes, TPM TIS SPI transfers deassert CS between
single-transfer messages that use cs_change to keep CS asserted across the
header, wait-state, and data phases, breaking TCG SPI flow control:

  tpm_tis_spi: probe of spi11.0 failed with error -110

Update both setup_se_xfer() and setup_gsi_xfer() to handle this condition.

Fixes: b99181cdf9fa ("spi-geni-qcom: remove manual CS control")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Viken Dadhaniya <viken.dadhaniya@xxxxxxxxxxxxxxxx>
---
 drivers/spi/spi-geni-qcom.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi-geni-qcom.c b/drivers/spi/spi-geni-qcom.c
index a04cdc1e5ad4..0618f6bd7878 100644
--- a/drivers/spi/spi-geni-qcom.c
+++ b/drivers/spi/spi-geni-qcom.c
@@ -449,10 +449,15 @@ static int setup_gsi_xfer(struct spi_transfer *xfer, struct spi_geni_master *mas
 		return ret;
 	}
 
-	if (!xfer->cs_change) {
-		if (!list_is_last(&xfer->transfer_list, &spi->cur_msg->transfers))
-			peripheral.fragmentation = FRAGMENTATION;
-	}
+	/*
+	 * Set fragmentation to keep CS asserted after this transfer when:
+	 *  - non-last transfer with cs_change=0: keep CS between chained transfers
+	 *  - last transfer with cs_change=1: keep CS asserted after the message
+	 *    (e.g. TPM TIS SPI uses cs_change=1 on single-transfer messages to
+	 *     keep CS asserted across header, wait-state and data phases)
+	 */
+	peripheral.fragmentation = list_is_last(&xfer->transfer_list, &spi->cur_msg->transfers) ?
+				   xfer->cs_change : !xfer->cs_change;
 
 	if (peripheral.cmd & SPI_RX) {
 		dmaengine_slave_config(mas->rx, &config);
@@ -858,10 +863,16 @@ static int setup_se_xfer(struct spi_transfer *xfer,
 		mas->cur_xfer_mode = GENI_SE_DMA;
 	geni_se_select_mode(se, mas->cur_xfer_mode);
 
-	if (!xfer->cs_change) {
-		if (!list_is_last(&xfer->transfer_list, &spi->cur_msg->transfers))
-			m_params = FRAGMENTATION;
-	}
+	/*
+	 * Set FRAGMENTATION to keep CS asserted after this transfer when:
+	 *  - non-last transfer with cs_change=0: keep CS between chained transfers
+	 *  - last transfer with cs_change=1: keep CS asserted after the message
+	 *    (e.g. TPM TIS SPI uses cs_change=1 on single-transfer messages to
+	 *     keep CS asserted across header, wait-state and data phases)
+	 */
+	if (list_is_last(&xfer->transfer_list, &spi->cur_msg->transfers) ?
+	    xfer->cs_change : !xfer->cs_change)
+		m_params = FRAGMENTATION;
 
 	/*
 	 * Lock around right before we start the transfer since our

---
base-commit: e7d700e14934e68f86338c5610cf2ae76798b663
change-id: 20260528-fix-spi-fragmentation-bit-logic-880394337ff9

Best regards,
--  
Viken Dadhaniya <viken.dadhaniya@xxxxxxxxxxxxxxxx>