From mboxrd@z Thu Jan 1 00:00:00 1970 From: Karl Beldan Subject: Re: [PATCH] ARM: dts: da850: Add basic DTS for the L138/C6748 Dev Kit Date: Thu, 4 Aug 2016 23:43:49 +0000 Message-ID: <20160804234349.GA4391@gobelin> References: <20160804144332.4841-1-kbeldan@baylibre.com> <20160804182902.GA22499@rob-hp-laptop> <20160804210326.GE15013@gobelin> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Rob Herring Cc: Mark Rutland , "devicetree@vger.kernel.org" , karl.beldan+oss@gmail.com, Peter Hurley , Kevin Hilman , Russell King , "linux-arm-kernel@lists.infradead.org" List-Id: devicetree@vger.kernel.org On Thu, Aug 04, 2016 at 04:13:10PM -0500, Rob Herring wrote: > +Peter H > > On Thu, Aug 4, 2016 at 4:03 PM, Karl Beldan wrote: > > On Thu, Aug 04, 2016 at 01:29:02PM -0500, Rob Herring wrote: > >> On Thu, Aug 04, 2016 at 02:43:32PM +0000, Karl Beldan wrote: > >> > The LCDK is the successor to the late Hawkboard and has the same machine > >> > number. > >> > Among the differences are the flash (16bits vs 8bits) and some pins > >> > (MMC, LEDs, buttons, some external connectors), however the main > >> > components remain the same (eth. PHY, Audio Codec, Video decoder and > >> > DAC) except for the main PMIC, different and hard-wired on the LCDK (the > >> > LDOs and DCDCs are always ON). > >> > A DT-only boot with this addition gives functional uart, reboot via > >> > watchdog, rtc, ethernet and MMC (I added the CD gpio for the MMC > >> > although davinci_mmc doesn't call yet the mmc core OF facilities). > > [...] > > >> > + aliases { > >> > + serial2 = &serial2; > >> > + }; > >> > + > >> > + chosen { > >> > + bootargs = "console=ttyS2,115200n8 earlycon"; > >> > >> You don't need console with stdout-path set. And really, earlycon should > >> not be the default. > >> > > Ok for earlycon. > > > > For the console, I thought likewise .. until I _struggled_ to understand > > why the console was disappearing under my feet. > > It seemed even stranger when I started looking at the codepath because > > drivers/of/base.c would properly add_preferred_console as expected after > > the corresponding UART was added. But the reality was there, without it > > the console was not like stdout-path. > > Among the commits that could instill doubt as to whether stdout-path > > rules is f64255b5072d: > > "The assumption that at least 1 preferred console will be registered > > when the stdout-path property is set is invalid, which can result in > > _no_ consoles.", though it didn't answer my question. > > I started looking whether tty0 was not getting in the way and in the end > > I came up with setting console. > > But you seem affirmative. > > There have been some issues in this area, but I thought they were in > conjunction with earlycon and solved now. This is a fairly common > review request for dts files, so I'm surprised if it doesn't work > right. Maybe having tty0 or not has some influence. Or people just > accept review comments without testing or caring... > I can assure you I tested without early{con,printk} ;). Now I have just rechecked the codepaths and something caught my attention in kernel/printk/printk.c:__add_preferred_console(): if console_cmdline is empty selected_console gets unconditionally set to zero ! Knowing this I confirmed by replacing with idx (works), and also by using ttyS0 (i.e. alias serial0 = &uart2) (works), this would not affect DTs using serial0. It's late here so I'll stop there. Karl