linux-kernel - Re: [PATCH v8 1/2] dmaengine: qcom: gpi: Add GPI Block event interrupt support

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Message-ID: <vdd33houteml2inilry6vkqdpdm7vykcqb5vf66sdhq5knlfhr@mzlrb5babocx>
Date: Sat, 27 Sep 2025 01:35:53 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Jyothi Kumar Seerapu <jyothi.seerapu@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>,
        Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>,
        Viken Dadhaniya <quic_vdadhani@...cinc.com>,
        Andi Shyti <andi.shyti@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, quic_vtanuku@...cinc.com
Subject: Re: [PATCH v8 1/2] dmaengine: qcom: gpi: Add GPI Block event
 interrupt support

On Thu, Sep 25, 2025 at 05:30:34PM +0530, Jyothi Kumar Seerapu wrote:
> From: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
> 
> 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.
> 
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
> ---
> 
> v7 -> v8:
>    - Removed duplicate sentence in commit description
> 
> 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(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>


-- 
With best wishes
Dmitry