linux-kernel - RE: [PATCH v3] i2c: tegra: Share same DMA channel for RX and TX

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Message-ID: <SJ1PR12MB6339FC0B9BB57D1D2300D46CC0869@SJ1PR12MB6339.namprd12.prod.outlook.com>
Date:   Wed, 22 Mar 2023 12:00:36 +0000
From:   Akhil R <akhilrajeev@...dia.com>
To:     Jonathan Hunter <jonathanh@...dia.com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "digetx@...il.com" <digetx@...il.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "sumit.semwal@...aro.org" <sumit.semwal@...aro.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "wsa@...nel.org" <wsa@...nel.org>
Subject: RE: [PATCH v3] i2c: tegra: Share same DMA channel for RX and TX

> On 22/03/2023 10:24, Akhil R wrote:
> > Allocate only one DMA channel for I2C and share it for both TX and RX
> > instead of using two different DMA hardware channels with the same
> > slave ID. Since I2C supports only half duplex, there is no impact on
> > perf with this.
> >
> > Signed-off-by: Akhil R <akhilrajeev@...dia.com>
> 
> Just to confirm. This impacts all Tegra devices from Tegra20 to the
> latest. Does this work for all Tegra and the different DMA controllers
> that they have?
> 
Yes, It should. I could see in the APB DMA driver that the same channel
could be used for TX and RX and the direction is configured only during
dma_prep_*() calls.
I did not test it on a Tegra with APB DMA, but since it works very similar
to GPC DMA there should not be any impact.

Regards,
Akhil
--
nvpublic