From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Walleij Subject: Re: [PATCH 1/5] dmaengine: add ep93xx DMA support Date: Wed, 25 May 2011 22:47:14 +0200 Message-ID: References: <20110525195413.GC2996@acer> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Cc: linux-arm-kernel@lists.infradead.org, Vinod Koul , linux-kernel@vger.kernel.org, hsweeten@visionengravers.com, ryan@bluewatersys.com, Dan Williams , Grant Likely , spi mailing list To: Mika Westerberg Return-path: In-Reply-To: <20110525195413.GC2996@acer> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-spi.vger.kernel.org 2011/5/25 Mika Westerberg : > I re-checked the specs and indeed, as discussed previously, it is clear that > Cirrus (or ARM) copied the interface from other. Even the wording in the > document is identical in many places. However, in ep93xx User's Guide, there > is no mention about SSP being AMBA PrimeCell peripheral. For UARTs it is > mentioned... go figure. > > There are differences also, some of the bits in control registers are in > different places. Interrupt registers are completely different and there is no > DMA control register at all. The same things we discussed before. But it really does not matter. The amba-pl022.c driver has all the same deviations for things called "PL023" that are not pure PL022 either. I just made the driver a bit more flexible, supporting both. If the people doing drivers/usb/musb/* had done the same thing we would have had what, 5 drivers for similar hardware? > Back then, it wasn't known how the M2M DMA interface (the one used > by SSP and IDE) was going to be implemented. But I knew, having just written the needed extensions to dmaengine. And I said so. But I realize I'm maybe not considered an authoritative source on the subject, and I'm biased. > IMHO it is better to have ep93xx implementation on its own driver since it is > not a real AMBA PL022 peripheral but some weird hack made by Cirrus (although > my opinions are bit biased). I disagree because it's IMO at first sight no more deviant than our "PL023" variants that still use the same pl022 driver. Is there some inexepensive hardware with EP93xx I can get to fix this myself? Yours, Linus Walleij