From: Santosh Shilimkar <santosh.shilimkar@ti.com>
To: Vinod Koul <vinod.koul@intel.com>
Cc: <dmaengine@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <devicetree@vger.kernel.org>,
Sandeep Nair <sandeep_n@ti.com>,
Russell King <linux@arm.linux.org.uk>,
Grant Likely <grant.likely@linaro.org>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH] dma: Add Keystone Packet DMA Engine driver
Date: Tue, 18 Mar 2014 12:19:31 -0400 [thread overview]
Message-ID: <53287213.3060705@ti.com> (raw)
In-Reply-To: <20140318152444.GC1976@intel.com>
On Tuesday 18 March 2014 11:24 AM, Vinod Koul wrote:
> On Mon, Mar 17, 2014 at 03:37:47PM -0400, Santosh Shilimkar wrote:
>>>> To simplify this bit more, you can think of this as DMA channels, flows
>>>> are allocated and DMA channels are enabled by DMA engine and they remains
>>>> enabled always as long as the channel in use. Enablling dma channel
>>>> actually don't start the DMA transfer but just sets up the connection/pipe
>>>> with peripheral and memory and vice a versa.
>>>>
>>>> All the descriptor management, triggering, sending completion interrupt or
>>>> hardware signal to DMAEngine all managed by centralised QMSS.
>>>>
>>>> Actual copy of data is still done by DMA hardware but its completely
>>>> transparent to software. DMAEngine hardware takes care of that in the
>>>> backyard.
>>> So you will use the dmaengine just for setting up the controller. Not for actual
>>> transfers. Those would be governed by the QMSS, right?
>>>
>> Correct.
>>
>>> This means that someone expecting to use dmaengine API will get confused about
>>> this and doing part (alloc) thru dmaengine and rest (transfers) using some other
>>> API. This brings to me the design approach, does it really make sense creating
>>> dmaengine driver for this when we are not fully complying to the API
>>>
>> Thats fair. The rationale behind usage of DMEngine was that its the closest
>> available subsystem which can be leveraged for this hardware. We can
>> pretty much use all the standard DMAEngine device tree parsing as well as
>> the config API to setup DMAs.
>>
>> I think you made your stand clear, just to confirm, you don't prefer this
>> driver to be a DMAEngine driver considering it doesn't fully complying to
>> the APIs. We could document the deviation of 'transfer' handling to avoid
>> any confusion.
> Yup, a user will just get confused as the driver doenst conform the dmaengine
> API. Unless someone comes up witha strong argument on why it should be
> dmaengine driver and what befits we see form such a model, i would like a
> damengine driver to comply to standard API and usage.
>
OK thanks !!
Regards,
Santosh
prev parent reply other threads:[~2014-03-18 16:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-28 22:56 [PATCH] dma: Add Keystone Packet DMA Engine driver Santosh Shilimkar
2014-02-28 23:14 ` Arnd Bergmann
2014-02-28 23:44 ` Santosh Shilimkar
2014-03-05 2:26 ` Santosh Shilimkar
2014-03-03 9:34 ` Shevchenko, Andriy
2014-03-11 10:23 ` Vinod Koul
2014-03-11 19:50 ` Santosh Shilimkar
2014-03-12 16:00 ` Vinod Koul
2014-03-12 21:16 ` Santosh Shilimkar
2014-03-17 4:42 ` Vinod Koul
2014-03-17 19:37 ` Santosh Shilimkar
2014-03-18 15:24 ` Vinod Koul
2014-03-18 15:38 ` Arnd Bergmann
2014-03-18 15:51 ` Vinod Koul
2014-03-18 16:22 ` Santosh Shilimkar
2014-03-18 16:40 ` Arnd Bergmann
2014-03-18 16:19 ` Santosh Shilimkar [this message]
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