From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: amba-pl011 complains about DMA for bcm2835 where it is not supported Date: Mon, 27 Oct 2014 23:59:42 +0000 Message-ID: <20141027235942.GY27405@n2100.arm.linux.org.uk> References: <20141027234430.GA1788@haysend> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:46221 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752752AbaJ0X7t (ORCPT ); Mon, 27 Oct 2014 19:59:49 -0400 Content-Disposition: inline In-Reply-To: <20141027234430.GA1788@haysend> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Piotr =?iso-8859-1?Q?Kr=F3l?= Cc: linux-serial@vger.kernel.org, jslaby@suse.cz, gregkh@linuxfoundation.org On Tue, Oct 28, 2014 at 12:44:31AM +0100, Piotr Kr=F3l wrote: > Hi all, > according to BCM2835 ARM Peripherals spec DMA is optional functionali= ty > for ARM PL011 UART and it is not supported on this SoC. It looks like > amba-pl011 search for device tree property (dma-names) unconditionall= y, > what leads to error message: >=20 > of_dma_request_slave_channel: dma-names property of node '/soc/uart@7= e201000' missing or empty > uart-pl011 20201000.uart: no DMA platform data >=20 > I assume that if it is possible that amba-pl011 can be without DMA we > should check if DMA is supported and then try to read properties. Is > there any known method for checking dma support ? If yes that I would= be > glad for any pointers. >=20 > Let me know if I should ignore/accept this error message or there is > some code fix needed. A great many implementations of PL011 do not have DMA support (some hav= e DMA support but its well broken.) The driver has always supported PIO mode, and continues to do so. --=20 =46TTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-serial"= in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html