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From: Nicolin Chen <nicoleotsuka-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Cc: vinod.koul-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	dmaengine-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	gnurou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org,
	ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org
Subject: Re: [PATCH v2 2/2] dmaengine: tegra210-adma: Add memcpy support
Date: Tue, 6 Sep 2016 10:21:28 -0700	[thread overview]
Message-ID: <20160906172127.GA966@Asurada-Nvidia> (raw)
In-Reply-To: <f9850c0c-a4a9-4d5f-eaa9-c1fd39b72870-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>

On Tue, Sep 06, 2016 at 12:52:03PM +0100, Jon Hunter wrote:
> > +	/* TODO: ADMA should support up to 8 chunks or periods */
> > +	desc->num_periods = 1;
> > +	desc->buf_len = buf_len;
> > +	desc->period_len = buf_len;

> What would be the benefit of using 8 periods here? My understanding is
> that you will get an interrupt per period and do you really want this
> for memcpy?

You are right about the interrupt. And it doesn't seem to be
beneficial unless the period size is over the limitation of
Transfer Count, which is rare but might theoretically exist?

I admit the "TODO" word here is a bit misleading for memcpy.
I can remove the word and write a more appropriate comments.

WARNING: multiple messages have this Message-ID (diff)
From: Nicolin Chen <nicoleotsuka@gmail.com>
To: Jon Hunter <jonathanh@nvidia.com>
Cc: vinod.koul@intel.com, linux-kernel@vger.kernel.org,
	linux-tegra@vger.kernel.org, dmaengine@vger.kernel.org,
	gnurou@gmail.com, thierry.reding@gmail.com,
	swarren@wwwdotorg.org, ldewangan@nvidia.com
Subject: Re: [PATCH v2 2/2] dmaengine: tegra210-adma: Add memcpy support
Date: Tue, 6 Sep 2016 10:21:28 -0700	[thread overview]
Message-ID: <20160906172127.GA966@Asurada-Nvidia> (raw)
In-Reply-To: <f9850c0c-a4a9-4d5f-eaa9-c1fd39b72870@nvidia.com>

On Tue, Sep 06, 2016 at 12:52:03PM +0100, Jon Hunter wrote:
> > +	/* TODO: ADMA should support up to 8 chunks or periods */
> > +	desc->num_periods = 1;
> > +	desc->buf_len = buf_len;
> > +	desc->period_len = buf_len;

> What would be the benefit of using 8 periods here? My understanding is
> that you will get an interrupt per period and do you really want this
> for memcpy?

You are right about the interrupt. And it doesn't seem to be
beneficial unless the period size is over the limitation of
Transfer Count, which is rare but might theoretically exist?

I admit the "TODO" word here is a bit misleading for memcpy.
I can remove the word and write a more appropriate comments.

  parent reply	other threads:[~2016-09-06 17:21 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-03  0:32 [PATCH v2 0/2] Add memcpy support for tegra210-adma Nicolin Chen
2016-09-03  0:32 ` [PATCH v2 1/2] dmaengine: tegra210-adma: Add pre-check for cyclic callback Nicolin Chen
     [not found] ` <cover.1472857934.git.nicoleotsuka-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-09-03  0:32   ` [PATCH v2 2/2] dmaengine: tegra210-adma: Add memcpy support Nicolin Chen
2016-09-03  0:32     ` Nicolin Chen
     [not found]     ` <738e0f1560436d613d9a7dab2fd540abea9503d3.1472857934.git.nicoleotsuka-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2016-09-06 11:52       ` Jon Hunter
2016-09-06 11:52         ` Jon Hunter
     [not found]         ` <f9850c0c-a4a9-4d5f-eaa9-c1fd39b72870-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2016-09-06 17:21           ` Nicolin Chen [this message]
2016-09-06 17:21             ` Nicolin Chen
2016-09-06 11:33   ` [PATCH v2 0/2] Add memcpy support for tegra210-adma Jon Hunter
2016-09-06 11:33     ` Jon Hunter
     [not found]     ` <319ca097-4b10-83b9-841c-52adccbb48ad-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2016-09-06 12:03       ` Dmitry Osipenko
2016-09-06 12:03         ` Dmitry Osipenko
2016-09-06 13:04         ` Jon Hunter
2016-09-06 13:04           ` Jon Hunter
     [not found]           ` <6f45ff6e-5fa7-7aca-154c-85cf235aa62f-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
2016-09-06 13:46             ` Jon Hunter
2016-09-06 13:46               ` Jon Hunter
2016-09-06 14:27               ` Dmitry Osipenko

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