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

[Jonathan Marek <jonathan@marek.ca>]

should have another Fixes tag for the GSI xfer fix, otherwise LTGM

Reviewed-by: Jonathan Marek <jonathan@marek.ca>

On 5/28/26 3:03 PM, Viken Dadhaniya wrote:
> 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@vger.kernel.org
> Signed-off-by: Viken Dadhaniya <viken.dadhaniya@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..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@oss.qualcomm.com>
>