TPM TIS SPI probe fails with:

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

TPM TIS SPI sets cs_change=1 on single-transfer messages to keep CS
asserted across the header, wait-state, and data phases of a transaction.
CS deassertion between these phases violates the TCG SPI flow control
specification.

This bug was introduced by commit b99181cdf9fa ("spi-geni-qcom: remove
manual CS control"), which replaced manual CS control with automatic CS
control via the FRAGMENTATION bit. The FRAGMENTATION bit controls CS
behavior after a transfer: when set to 1, CS remains asserted; when
cleared to 0, CS is deasserted.

The commit correctly sets FRAGMENTATION for non-last transfers with
cs_change=0 to keep CS asserted between chained transfers, but misses the
case where cs_change=1 is set on the last transfer. When cs_change=1 on
the last transfer, the client requests CS to remain asserted after the
message completes, so FRAGMENTATION must be set to 1 in this case as well.

Fix setup_se_xfer() to set FRAGMENTATION when cs_change=1 on the last
transfer.

Also fix the same missing case in setup_gsi_xfer() and correct it to
write 1 instead of the raw bitmask FRAGMENTATION (value 4) to
peripheral.fragmentation. This field is a 1-bit boolean consumed by
gpi_create_spi_tre() via u32_encode_bits(..., TRE_SPI_GO_FRAG). Writing 4
to a 1-bit field causes u32_encode_bits() to mask it to 0, silently
disabling the FRAGMENTATION bit in the GPI TRE regardless of the
cs_change logic.

Fixes: b99181cdf9fa ("spi-geni-qcom: remove manual CS control")
Cc: stable@vger.kernel.org
Reviewed-by: Jonathan Marek <jonathan@marek.ca>
Signed-off-by: Viken Dadhaniya <viken.dadhaniya@oss.qualcomm.com>
---
Changes in v2:
- Updated commit log.
- Fixed typo in code comment: s/keep CS between/keep CS asserted between/.
- Link to v1: https://patch.msgid.link/20260529-fix-spi-fragmentation-bit-logic-v1-1-3b30f1a3dd7d@oss.qualcomm.com
---
 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..26e723cfea61 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 asserted 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 asserted 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@oss.qualcomm.com>

On Tue, 09 Jun 2026 14:13:09 +0530, Viken Dadhaniya wrote:
> spi: qcom-geni: Fix cs_change handling on the last transfer

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-7.1

Thanks!

[1/1] spi: qcom-geni: Fix cs_change handling on the last transfer
      https://git.kernel.org/broonie/spi/c/5ac5ec84734f

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark