From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 28 Sep 2017 21:52:38 +0530
From: Vinod Koul <vinod.koul@intel.com>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	Laxman Dewangan <ldewangan@nvidia.com>,
	Peter De Schrijver <pdeschrijver@nvidia.com>,
	Prashant Gaikwad <pgaikwad@nvidia.com>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Rob Herring <robh+dt@kernel.org>, linux-tegra@vger.kernel.org,
	devicetree@vger.kernel.org, dmaengine@vger.kernel.org,
	linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA
 controller
Message-ID: <20170928162238.GF30097@localhost>
References: <cover.1506380746.git.digetx@gmail.com>
 <0a45e058baba72124b91c663ce1d908d275f4044.1506380746.git.digetx@gmail.com>
 <20170928092949.GB30097@localhost>
 <b601b829-d87f-99e0-dcf9-ad3f9a7195df@gmail.com>
 <260fa409-0d07-ec9e-9e3b-fb08255026d8@gmail.com>
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List-ID: <linux-clk.vger.kernel.org>

On Thu, Sep 28, 2017 at 05:35:59PM +0300, Dmitry Osipenko wrote:
> On 28.09.2017 17:06, Dmitry Osipenko wrote:
> > On 28.09.2017 12:29, Vinod Koul wrote:
> >>> +	default:
> >>> +		return -EINVAL;
> >>> +	}
> >>> +
> >>> +	ahb_seq  = burst << TEGRA_AHBDMA_CHANNEL_AHB_BURST_SHIFT;
> >>> +	ahb_seq |= TEGRA_AHBDMA_CHANNEL_ADDR_WRAP;
> >>> +	ahb_seq |= TEGRA_AHBDMA_CHANNEL_INTR_ENB;
> >>> +
> >>> +	writel_relaxed(ahb_seq,
> >>> +		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_SEQ);
> >>> +
> >>> +	writel_relaxed(ahb_addr,
> >>> +		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_PTR);
> >>
> >> oh no, you don't write to HW here. This can be called anytime when you have
> >> txn running! You should save these and use them in prep_ calls.
> >>
> > 
> > BTW, some of the DMA drivers have exactly the same problem. I now see that it is
> > actually documented explicitly in provider.txt, but that's inconsistent across
> > the actual drivers.
> > 
> 
> Also, shouldn't prep_ and dma_slave_config be protected with locking? I don't
> see DMA core doing any locking and seems none of the drivers too.

In prep when you modify the list yes (with vchan I suspect that maybe taken
care), but in general yes driver needs to do that

-- 
~Vinod