Re: [PATCH] dmaengine: qcom: gpi: Fix SE ID and SE Protocol fields widths in SCRATCH_0

[Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>]

On 7/20/26 5:27 PM, Chandana Kishori Chiluveru wrote:
> GPII_n_CH_k_SCRATCH_0_SEID is currently defined as GENMASK(2, 0), only
> 3 bits wide. Serial engine indices >= 8 get silently truncated by
> FIELD_PREP()/u32_encode_bits() when written into the scratch register,
> causing the GPI channel to bind to the wrong serial engine. The
> channel allocate command still succeeds (it doesn't require the
> target SE to respond), but the subsequent channel start command times
> out waiting for hardware to complete the handoff to the (incorrectly
> bound) SE, and gpi_send_cmd() returns -EIO leading to GSI usecase failures
> for SE8 and SE9 serial engines.
> 
> Older documentation, such as the SDM845 hardware programming guide,
> describes the SE ID field as bits [2:0]. More recent QUP hardware
> documentation defines the field as bits [3:0]. Use the wider definition
> to match current hardware documentation while remaining compatible with
> existing platforms and enabling serial engine IDs greater than 7.
> 
> Also update the SE Protocol field definition to match the documented
> register layout and keep both fields correctly packed.
> 
> Fixes: 5d0c3533a19f ("dmaengine: qcom: Add GPI dma driver")
> Signed-off-by: Chandana Kishori Chiluveru <chandana.chiluveru@oss.qualcomm.com>
> ---
>  drivers/dma/qcom/gpi.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
> index a5055a6273af..8f09eaf4e714 100644
> --- a/drivers/dma/qcom/gpi.c
> +++ b/drivers/dma/qcom/gpi.c
> @@ -207,8 +207,8 @@ enum CNTXT_OFFS {
>  
>  /* Scratch registers */
>  #define GPII_n_CH_k_SCRATCH_0_OFFS(n, k)	(0x20060 + (0x4000 * (n)) + (0x80 * (k)))
> -#define GPII_n_CH_k_SCRATCH_0_SEID		GENMASK(2, 0)
> -#define GPII_n_CH_k_SCRATCH_0_PROTO		GENMASK(7, 4)
> +#define GPII_n_CH_k_SCRATCH_0_SEID		GENMASK(3, 0)
> +#define GPII_n_CH_k_SCRATCH_0_PROTO		GENMASK(6, 4)

There exist protocols, such as QSPI with id=9, so this surely can't
be right (unless there's another bitfield for that?)

Konrad