linux-kernel - RE: [PATCH v2 3/3] dmaengine: tegra: Add support for dma-channel-mask

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Message-ID: <SJ1PR12MB6339A665889F4F4B55AE81E5C0519@SJ1PR12MB6339.namprd12.prod.outlook.com>
Date:   Fri, 23 Sep 2022 16:22:51 +0000
From:   Akhil R <akhilrajeev@...dia.com>
To:     Jonathan Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        "thierry.reding@...il.com" <thierry.reding@...il.com>,
        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 3/3] dmaengine: tegra: Add support for dma-channel-mask

> >> Ah OK. I was wondering how this worked with 'channel_reg_size' but
> >> looking closer I see channel_reg_size is always SZ_64K. I wonder why we
> >> even bother having this parameter and don't use SZ_64K directly?
> > There is an offset from the base address which the per channel registers start.
> > Although this offset value happens to match with the channel_reg_size, this is
> > not actually the per channel register size.
> 
> Yes I see that, but I mean why do we even bother having this
> channel_reg_size parameter? Does not look like we need this (currently).
> All we need is ...
> 
>   tdc->chan_base_offset = TEGRA_GPCDMA_CHANNEL_BASE_ADDR_OFFSET +
>                           (i * SZ_64K);
> 
Ah. Ok. Got it now. Would add this as an improvement in another patch.

Thanks,
Akhil