linux-kernel - Re: [PATCH v4 0/2] Add Block event interrupt support for I2C protocol

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Message-ID: <pvcu35x7prqonlhptakepn5bdqm6skd4qmigvoavejyjj363ug@aemx3pd2po2v>
Date: Sat, 4 Jan 2025 01:09:26 +0100
From: Andi Shyti <andi.shyti@...nel.org>
To: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
Cc: Vinod Koul <vkoul@...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_msavaliy@...cinc.com, 
	quic_vtanuku@...cinc.com
Subject: Re: [PATCH v4 0/2] Add Block event interrupt support for I2C protocol

Hi,

this patch has been hanging here for a while, can we please have
someone from DMA and Qualcomm look at it?

Thanks,
Andi

On Tue, Dec 17, 2024 at 10:34:22PM +0530, Jyothi Kumar Seerapu wrote:
> The I2C driver gets an interrupt upon transfer completion.
> When handling multiple messages in 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 hardware to prevent interrupt
> generation and BEI is disabled when an interrupt is necessary.
> 
> Large I2C transfer can be divided into chunks of 8 messages internally.
> 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.
> 
> This optimization reduces transfer time from 168 ms to 48 ms for a
> series of 200 I2C write messages in a single transfer, with a
> clock frequency support of 100 kHz.
> 
> BEI optimizations are currently implemented for I2C write transfers only,
> as there is no use case for multiple I2C read messages in a single transfer
> at this time.
> 
> v3 -> v4:
>   - API's added for Block event interrupt with multi descriptor support 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.
>   - geni_i2c_gpi_multi_desc_xfer structure is added as a member of
>     struct geni_i2c_dev.
>   - Removed the changes of making I2C driver is dependent on GPI driver.
> 
> v2 -> v3:
>   - Updated commit description
>   - In I2C GENI driver, for i2c_gpi_cb_result moved the logic of
>     "!is_tx_multi_xfer" to else part.
>   - MIN_NUM_OF_MSGS_MULTI_DESC changed from 4 to 2
>   - Changes of I2C GENI driver to depend on the GPI driver moved
>     to patch3.
>   - Renamed gpi_multi_desc_process to gpi_multi_xfer_timeout_handler
>   - Added description for newly added changes in "qcom-gpi-dma.h" file.
> 
> v1 -> v2:
>   - DT changes are reverted for adding dma channel size as a new arg of
>     dma-cells property.
>   - DT binding change reveted for dma channel size as a new arg of
>     dma-cells property.
>   - In GPI driver, reverted the changes to parse the channel TRE size
>     from device tree.
>   - Made the changes in QCOM I2C geni driver to support the BEI
>     functionality with the existing TRE size of 64.
>   - Made changes in QCOM I2C geni driver as per the review comments.
>   - Fixed Kernel test robot reported compiltion issues.
> 
> 
> Jyothi Kumar Seerapu (2):
>   dmaengine: qcom: gpi: Add GPI Block event interrupt support
>   i2c: i2c-qcom-geni: Add Block event interrupt support
> 
>  drivers/dma/qcom/gpi.c             |   3 +
>  drivers/i2c/busses/i2c-qcom-geni.c | 275 ++++++++++++++++++++++++++---
>  include/linux/dma/qcom-gpi-dma.h   |   9 +
>  3 files changed, 262 insertions(+), 25 deletions(-)
> 
> -- 
> 2.17.1
>