linux-kernel - Re: [PATCH v1 1/3] dma: tegra: finer granularity residual for tx

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140521060012.GL21128@intel.com>
Date:	Wed, 21 May 2014 11:30:12 +0530
From:	Vinod Koul <vinod.koul@...el.com>
To:	Christopher Freeman <cfreeman@...dia.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Stephen Warren <swarren@...dia.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"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 v1 1/3] dma: tegra: finer granularity residual for
 tx_status

On Wed, May 07, 2014 at 03:37:45PM -0700, Christopher Freeman wrote:
> On Wed, May 07, 2014 at 09:37:25AM -0700, Stephen Warren wrote:
> > On 05/06/2014 03:22 PM, Christopher Freeman wrote:
> > > Get word-level granularity from hardware for calculating
> > > the transfer count remaining.
> > 
> > > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
> > 
> > > +static int tegra_dma_wcount_in_bytes(struct dma_chan *dc)
> > 
> > A lot of the code in this function is identical to the code in
> > tegra_dma_terminate_all() which does the same thing. Can this be pulled
> > out into a shared utility function?
> > 
> I'll look at making utility functions for ISR handling and the calculations for the byte counts.
> 
> > > +	tegra_dma_pause(tdc, true);
> > 
> > Is this continual pausing/resuming of the DMA operation going to
> > negatively affect performance?
> > 
> I tried testing the performance impact and each call took about 20 uS.  And of
> course, the client would have to be calling this constantly.
But why do we need to pause, cant we read the status form HW and report..?

-- 
~Vinod
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/