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

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Message-ID: <Z89TC7fKzmmeu6tW@vaman>
Date: Tue, 11 Mar 2025 02:30:59 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
Cc: 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_msavaliy@...cinc.com,
	quic_vtanuku@...cinc.com
Subject: Re: [PATCH v5 RESEND 1/2] dmaengine: qcom: gpi: Add GPI Block event
 interrupt support

On 12-02-25, 17:35, 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.

That sounds good but I dont like the idea that we add a custom interface
for this. Please use DMA_PREP_INTERRUPT instead. Adding this flag should
trigger N interrupts, absence of this should lead to Block events only

-- 
~Vinod