On Wed, Sep 03, 2025 at 01:00:58PM +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.
>
> Large I2C transfer can be divided into chunks of messages internally.
> Interrupts are not expected for the messages for which BEI bit set,
> only the last message triggers an interrupt, indicating the completion of
> N messages. This BEI mechanism enhances overall transfer efficiency.
>
> This BEI mechanism enhances overall transfer efficiency.
Duplicate phrase.
>
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@xxxxxxxxxxx>
> ---
>
> v6 -> v7:
> - The design has been modified to configure BEI for interrupt
> generation either:
> After the last I2C message, if sufficient TREs are available, or
> After a specific I2C message, when no further TREs are available.
> - In the GPI driver, passed the flags argumnetr to the gpi_create_i2c_tre function
> and so avoided using external variables for DMA_PREP_INTERRUPT status.
>
> 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 | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
> index 8e87738086b2..66bfea1f156d 100644
> --- a/drivers/dma/qcom/gpi.c
> +++ b/drivers/dma/qcom/gpi.c
> @@ -1619,7 +1619,8 @@ gpi_peripheral_config(struct dma_chan *chan, struct dma_slave_config *config)
> }
>
> static int gpi_create_i2c_tre(struct gchan *chan, struct gpi_desc *desc,
> - struct scatterlist *sgl, enum dma_transfer_direction direction)
> + struct scatterlist *sgl, enum dma_transfer_direction direction,
> + unsigned long flags)
> {
> struct gpi_i2c_config *i2c = chan->config;
> struct device *dev = chan->gpii->gpi_dev->dev;
> @@ -1684,6 +1685,9 @@ 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 (!(flags & DMA_PREP_INTERRUPT))
> + tre->dword[3] |= u32_encode_bits(1, TRE_FLAGS_BEI);
> }
>
> for (i = 0; i < tre_idx; i++)
> @@ -1827,6 +1831,9 @@ gpi_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> return NULL;
> }
>
> + if (!(flags & DMA_PREP_INTERRUPT) && (nr - nr_tre < 2))
> + return NULL;
Comment in the source file.
> +
> gpi_desc = kzalloc(sizeof(*gpi_desc), GFP_NOWAIT);
> if (!gpi_desc)
> return NULL;
> @@ -1835,7 +1842,7 @@ gpi_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
> if (gchan->protocol == QCOM_GPI_SPI) {
> i = gpi_create_spi_tre(gchan, gpi_desc, sgl, direction);
> } else if (gchan->protocol == QCOM_GPI_I2C) {
> - i = gpi_create_i2c_tre(gchan, gpi_desc, sgl, direction);
> + i = gpi_create_i2c_tre(gchan, gpi_desc, sgl, direction, flags);
> } else {
> dev_err(dev, "invalid peripheral: %d\n", gchan->protocol);
> kfree(gpi_desc);
> --
> 2.34.1
>
--
With best wishes
Dmitry
