From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753931Ab2LQV7e (ORCPT ); Mon, 17 Dec 2012 16:59:34 -0500 Received: from rs130.luxsci.com ([72.32.115.17]:54121 "EHLO rs130.luxsci.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752768Ab2LQV7b (ORCPT ); Mon, 17 Dec 2012 16:59:31 -0500 Message-ID: <50CF9580.4050300@firmworks.com> Date: Mon, 17 Dec 2012 11:58:24 -1000 From: Mitch Bradley User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Stephen Warren CC: Laxman Dewangan , grant.likely@secretlab.ca, rob.herring@calxeda.com, linux-doc@vger.kernel.org, gregkh@linuxfoundation.org, devicetree-discuss@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-tegra@vger.kernel.org, jslaby@suse.cz, alan@linux.intel.com Subject: Re: [PATCH] serial: tegra: add serial driver References: <1355746249-15347-1-git-send-email-ldewangan@nvidia.com> <50CF9043.8030308@wwwdotorg.org> In-Reply-To: <50CF9043.8030308@wwwdotorg.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Lux-Comment: Message qBHLwNan022427 sent by user #11875 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/17/2012 11:36 AM, Stephen Warren wrote: > On 12/17/2012 05:10 AM, Laxman Dewangan wrote: >> Nvidia's Tegra has multiple uart controller which supports: >> - APB dma based controller fifo read/write. >> - End Of Data interrupt in incoming data to know whether end >> of frame achieve or not. >> - Hw controlled RTS and CTS flow control to reduce SW overhead. > >> diff --git a/Documentation/devicetree/bindings/serial/nvidia,serial-tegra.txt b/Documentation/devicetree/bindings/serial/nvidia,serial-tegra.txt > >> +NVIDIA Tegra20/Tegra30 high speed (dma based) UART controller driver. >> + >> +Required properties: >> +- compatible : should be "nvidia,tegra20-hsuart", "nvidia,tegra30-hsuart". > > One question that isn't addressed here is: > > Tegra has 5 UARTs. All of them can use the existing 8250.c by specifying > compatible = "nvidia,tegra20-uart". The way it is supposed to work is that the compatible property should list "nvidia,tegra30-hsuart" first, followed by a fallback name that refers to the generic 8250 compatibility. Having the 8250.c driver bind to the more-specific tegra30-hsuart name is wrong. However, the 8250.c driver doesn't > support the DMA features of this driver. This driver is an alternate > driver for the same HW that allows DMA to be used with it, etc. > > Since DT is supposed to describe the HW, modifying the DT to change the > compatible value in order to select a different driver in Linux doesn't > seem correct, or is it? Is there any kind of precedent for how to select > different drivers for the same HW at run-time? I'd wondered about using > the sysfs bind/unbind "methods" from user-space as the driver selection > mechanism... > _______________________________________________ > devicetree-discuss mailing list > devicetree-discuss@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/devicetree-discuss >