linux-kernel - Re: [PATCH v3 07/12] soc: aspeed: xdma: Add user interface

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Message-Id: <700f857c-0d99-4e7e-a969-191c5afd10f8@www.fastmail.com>
Date:   Fri, 20 Dec 2019 07:46:18 +1030
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Eddie James" <eajames@...ux.ibm.com>,
        linux-aspeed@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        mark.rutland@....com, "Jason Cooper" <jason@...edaemon.net>,
        "Marc Zyngier" <maz@...nel.org>,
        "Rob Herring" <robh+dt@...nel.org>, tglx@...utronix.de,
        "Joel Stanley" <joel@....id.au>
Subject: Re: [PATCH v3 07/12] soc: aspeed: xdma: Add user interface



On Fri, 20 Dec 2019, at 02:30, Eddie James wrote:
> 
> On 12/18/19 7:19 PM, Andrew Jeffery wrote:
> >
> > On Thu, 19 Dec 2019, at 01:39, Eddie James wrote:
> >> +			mutex_unlock(&ctx->file_lock);
> >> +			return -EBUSY;
> >> +		}
> >> +	} else {
> >> +		mutex_lock(&ctx->file_lock);
> >> +
> >> +		rc = wait_event_interruptible(ctx->wait, !ctx->current_client);
> >> +		if (rc) {
> >> +			mutex_unlock(&ctx->file_lock);
> >> +			return -EINTR;
> >> +		}
> >> +	}
> >> +
> >> +	aspeed_xdma_start(ctx, &op, client->phys, client);
> >> +
> >> +	mutex_unlock(&ctx->file_lock);
> > Shouldn't we lift start_lock out of aspeed_xdma_start() use that here
> > instead of file_lock? I think that would mean that we could remove
> > file_lock.
> 
> 
> That wouldn't work with the reset though. The reset should hold 
> start_lock as well, but if a client is waiting here with start_lock, 
> we'd never get to the reset if the transfer doesn't complete. I think 
> file_lock is necessary.

Hmm, let me think about this some more.

Andrew