linux-kernel - Re: [PATCH v6 2/2] i2c: i2c-qcom-geni: Add Block event interrupt support

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Message-ID: <aICMDROkyjzBZFHo@vaman>
Date: Wed, 23 Jul 2025 12:45:25 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>,
	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 v6 2/2] i2c: i2c-qcom-geni: Add Block event interrupt
 support

On 22-07-25, 15:46, Dmitry Baryshkov wrote:
> On Tue, Jul 22, 2025 at 05:50:08PM +0530, Jyothi Kumar Seerapu wrote:
> > On 7/19/2025 3:27 PM, Dmitry Baryshkov wrote:
> > > On Mon, Jul 07, 2025 at 09:58:30PM +0530, Jyothi Kumar Seerapu wrote:
> > > > On 7/4/2025 1:11 AM, Dmitry Baryshkov wrote:
> > > > > On Thu, 3 Jul 2025 at 15:51, Jyothi Kumar Seerapu

[Folks, would be nice to trim replies]

> > > > Could you please confirm if can go with the similar approach of unmap the
> > > > processed TREs based on a fixed threshold or constant value, instead of
> > > > unmapping them all at once?
> > > 
> > > I'd still say, that's a bad idea. Please stay within the boundaries of
> > > the DMA API.
> > >
> > I agree with the approach you suggested—it's the GPI's responsibility to
> > manage the available TREs.
> > 
> > However, I'm curious whether can we set a dynamic watermark value perhaps
> > half the available TREs) to trigger unmapping of processed TREs ? This would
> > allow the software to prepare the next set of TREs while the hardware
> > continues processing the remaining ones, enabling better parallelism and
> > throughput.
> 
> Let's land the simple implementation first, which can then be improved.
> However I don't see any way to return 'above the watermark' from the DMA
> controller. You might need to enhance the API.

Traditionally, we set the dma transfers for watermark level and we get a
interrupt. So you might want to set the callback for watermark level
and then do mapping/unmapping etc in the callback. This is typical model
for dmaengines, we should follow that well

BR
-- 
~Vinod