On Tue, May 06, 2025 at 04:48:43PM +0530, Jyothi Kumar Seerapu wrote:
> GSI hardware generates an interrupt for each transfer completion.
> For multiple messages within a single transfer, this results in
> N interrupts for N messages, leading to significant software
> interrupt latency.
>
> To mitigate this latency, utilize Block Event Interrupt (BEI) mechanism.
> Enabling BEI instructs the GSI hardware to prevent interrupt generation
> and BEI is disabled when an interrupt is necessary.
>
> When using BEI, consider splitting a single multi-message transfer into
> chunks of 8 messages internally and so interrupts are not expected for
> the first 7 message completions, only the last message triggers
> an interrupt, indicating the completion of 8 messages.
>
> This BEI mechanism enhances overall transfer efficiency.
>
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseer...@quicinc.com>
> ---
> v5 ->v6:
> - For updating the block event interrupt bit, instead of relying on
> bei_flag, decision check is moved with DMA_PREP_INTERRUPT flag.
>
> v4 -> v5:
> - BEI flag naming changed from flags to bei_flag.
> - QCOM_GPI_BLOCK_EVENT_IRQ macro is removed from qcom-gpi-dma.h
> file, and Block event interrupt support is checked with bei_flag.
>
> v3 -> v4:
> - API's added for Block event interrupt with multi descriptor support for
> I2C is moved from qcom-gpi-dma.h file to I2C geni qcom driver file.
> - gpi_multi_xfer_timeout_handler function is moved from GPI driver to
> I2C driver.
>
> v2-> v3:
> - Renamed gpi_multi_desc_process to gpi_multi_xfer_timeout_handler
> - MIN_NUM_OF_MSGS_MULTI_DESC changed from 4 to 2
> - Added documentation for newly added changes in "qcom-gpi-dma.h" file
> - Updated commit description.
>
> v1 -> v2:
> - Changed dma_addr type from array of pointers to array.
> - To support BEI functionality with the TRE size of 64 defined in GPI
> driver,
> updated QCOM_GPI_MAX_NUM_MSGS to 16 and NUM_MSGS_PER_IRQ to 4.
>
> drivers/dma/qcom/gpi.c | 3 +++
> include/linux/dma/qcom-gpi-dma.h | 2 ++
> 2 files changed, 5 insertions(+)
>
> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
> index b1f0001cc99c..7e511f54166a 100644
> --- a/drivers/dma/qcom/gpi.c
> +++ b/drivers/dma/qcom/gpi.c
> @@ -1695,6 +1695,9 @@ static int gpi_create_i2c_tre(struct gchan *chan,
> struct gpi_desc *desc,
>
> tre->dword[3] = u32_encode_bits(TRE_TYPE_DMA, TRE_FLAGS_TYPE);
> tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_IEOT);
> +
> + if (!(i2c->dma_flags & DMA_PREP_INTERRUPT))
> + tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_BEI);
> }
>
> for (i = 0; i < tre_idx; i++)
> diff --git a/include/linux/dma/qcom-gpi-dma.h
> b/include/linux/dma/qcom-gpi-dma.h
> index 6680dd1a43c6..ebac0d3edff2 100644
> --- a/include/linux/dma/qcom-gpi-dma.h
> +++ b/include/linux/dma/qcom-gpi-dma.h
> @@ -65,6 +65,7 @@ enum i2c_op {
> * @rx_len: receive length for buffer
> * @op: i2c cmd
> * @muli-msg: is part of multi i2c r-w msgs
> + * @dma_flags: Flags indicating DMA capabilities
> */
> struct gpi_i2c_config {
> u8 set_config;
> @@ -78,6 +79,7 @@ struct gpi_i2c_config {
> u32 rx_len;
> enum i2c_op op;
> bool multi_msg;
> + unsigned int dma_flags;
Why do you need extra field instead of using
dma_async_tx_descriptor.flags?
> };
>
> #endif /* QCOM_GPI_DMA_H */
> --
> 2.17.1
>
--
With best wishes
Dmitry
