linux-kernel - Re: [PATCH v4 1/2] dmaengine: qcom: gpi: Add GPI Block event interrupt support

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Message-ID: <13c5b4d2-8fab-4ad2-98b7-1f71584509a6@quicinc.com>
Date: Tue, 7 Jan 2025 11:11:10 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>,
        Vinod Koul
	<vkoul@...nel.org>, Andi Shyti <andi.shyti@...nel.org>,
        Sumit Semwal
	<sumit.semwal@...aro.org>,
        Christian König
	<christian.koenig@....com>
CC: <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 v4 1/2] dmaengine: qcom: gpi: Add GPI Block event
 interrupt support



On 12/17/2024 10:34 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 internally. Interrupts are not expected for the first 7 message
chunks of 8 internally. This seems half statement to me. Something is 
missing to complete the statement.
> completions, only the last message triggers an interrupt,indicating
,indicating
here give space before.
> the completion of 8 messages.
> 
> This BEI mechanism enhances overall transfer efficiency.
> 
> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
> ---
> 
> 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 | 9 +++++++++
>   2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
> index 52a7c8f2498f..74eabcd1416d 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->flags & QCOM_GPI_BLOCK_EVENT_IRQ)
> +			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..d818c6a955e2 100644
> --- a/include/linux/dma/qcom-gpi-dma.h
> +++ b/include/linux/dma/qcom-gpi-dma.h
> @@ -15,6 +15,13 @@ enum spi_transfer_cmd {
>   	SPI_DUPLEX,
>   };
>   
> +/**
> + * define QCOM_GPI_BLOCK_EVENT_IRQ - Block event interrupt support
> + *
> + * This is used to enable/disable the Block event interrupt mechanism.
> + */
> +#define QCOM_GPI_BLOCK_EVENT_IRQ	BIT(0)
> +
>   /**
>    * struct gpi_spi_config - spi config for peripheral
>    *
> @@ -65,6 +72,7 @@ enum i2c_op {
>    * @rx_len: receive length for buffer
>    * @op: i2c cmd
>    * @muli-msg: is part of multi i2c r-w msgs
> + * @flags: true for block event interrupt support
>    */
>   struct gpi_i2c_config {
>   	u8 set_config;
> @@ -78,6 +86,7 @@ struct gpi_i2c_config {
>   	u32 rx_len;
>   	enum i2c_op op;
>   	bool multi_msg;
> +	bool flags;
can we better singular name instead of general name ?
something like bei_flag ? OR block_int_flag ?

>   };
>   
>   #endif /* QCOM_GPI_DMA_H */