Re: [PATCH v5 RESEND 1/2] dmaengine: qcom: gpi: Add GPI Block event interrupt support

[Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>]

On 2/12/2025 5:35 PM, 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.
> 
Acked-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@quicinc.com>
> ---
> 
> 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 52a7c8f2498f..d925a8156317 100644
> --- a/drivers/dma/qcom/gpi.c
> +++ b/drivers/dma/qcom/gpi.c
> @@ -1693,6 +1693,9 @@ 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->bei_flag)
> +			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..1060b7eac305 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
> + * @bei_flag: true for block event interrupt support
>    */
>   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;
> +	bool bei_flag;
>   };
>   
>   #endif /* QCOM_GPI_DMA_H */