linux-kernel - Re: [PATCH 1/2] dmaengine: sprd: delete enable opreation in probe

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Message-ID: <ZXb1RWaFWHVDx1wV@matsya>
Date:   Mon, 11 Dec 2023 17:10:53 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     liu kaiwei <liukaiwei086@...il.com>
Cc:     Kaiwei Liu <kaiwei.liu@...soc.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wenming Wu <wenming.wu@...soc.com>
Subject: Re: [PATCH 1/2] dmaengine: sprd: delete enable opreation in probe

On 06-12-23, 17:32, liu kaiwei wrote:
> On Fri, Nov 24, 2023 at 9:11 PM Vinod Koul <vkoul@...nel.org> wrote:
> >
> > On 02-11-23, 20:16, Kaiwei Liu wrote:
> > > From: "kaiwei.liu" <kaiwei.liu@...soc.com>
> >
> > Typo is subject line
> >
> > >
> > > In the probe of dma, it will allocate device memory and do some
> > > initalization settings. All operations are only at the software
> > > level and don't need the DMA hardware power on. It doesn't need
> > > to resume the device and set the device active as well. here
> > > delete unnecessary operation.
> >
> > Don't you need to read or write to the device? Without enable that wont
> > work right?
> >
> 
> Yes, it doesn't need to read or write to the device in the probe of DMA.
> We will enable the DMA when allocating the DMA channel.

So you will probe even if device is not present! I think it makes sense
to access device registers in probe!

-- 
~Vinod