From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liviu.Dudau@arm.com (Liviu Dudau) Date: Fri, 27 Feb 2015 14:06:00 +0000 Subject: [PATCH 1/2] arm64: juno: Add APB registers and LEDs using syscon In-Reply-To: References: <1424866589-2988-1-git-send-email-linus.walleij@linaro.org> <20150225135512.GE12377@arm.com> <20150225144756.GA905@e106497-lin.cambridge.arm.com> <20150225150023.GJ12377@arm.com> <20150225151157.GC905@e106497-lin.cambridge.arm.com> Message-ID: <20150227140600.GZ905@e106497-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Feb 27, 2015 at 01:07:42PM +0000, Linus Walleij wrote: > On Wed, Feb 25, 2015 at 4:11 PM, Liviu Dudau wrote: > > On Wed, Feb 25, 2015 at 03:00:23PM +0000, Will Deacon wrote: > >> On Wed, Feb 25, 2015 at 02:47:56PM +0000, Liviu Dudau wrote: > >> > On Wed, Feb 25, 2015 at 01:55:12PM +0000, Will Deacon wrote: > >> > > On Wed, Feb 25, 2015 at 12:16:29PM +0000, Linus Walleij wrote: > >> > > > This defines the Juno "APB system registers" as a syscon device, > >> > > > and all the LEDs controlled by the APB system registers right > >> > > > below it using the syscon LEDs driver on top of syscon. Define > >> > > > LED0 for heartbeat, LED1 for MMC0 activity and the following > >> > > > four LEDs indicating CPU activity using the Linux-specific > >> > > > DT bindings for triggers. > >> > > > > >> > > > This is the pattern and same drivers as used on the legacy > >> > > > platform device trees for the ARM Integrators and the RealView > >> > > > PB1176. > >> > > > >> > > Stupid question, but where are these LEDs located on the platform? I tried > >> > > enabling this, but all it seemed to do was make hackbench slightly slower :) > >> > > >> > http://infocenter.arm.com/help/topic/com.arm.doc.ddi0524c/deb1353593789871.html > >> > > >> > Section 1.3, look at the left hand side, above the user push buttons. > >> > >> Right, so these LEDs are *inside* the case. Is that really something worth > >> enabling for defconfig? > > > > Depends on the case :) You might have a nice cutout in the plastic of the VExpress > > box, or have your own custom acrylic box. > > Of course I take off the lid, who doesn't want to see the nice electronics. > This is analogous to using some other naked ARM reference design > like the Versatile or the RealView PB1176 where you can just put your > fingers on the board if you like. > > > Maybe Linus can explain to us why he thinks this functionality is useful given > > that quite a lot of people tend to use the Juno boards inside the original boxes > > for fear of ESD accidents. > > Wut? Ask the guy who designed the box. > > Notice that the SD card slot is *ALSO* inside the box, do you mean we > should then also delete the uSD card support added in > commit 71f867ec130e3cc8e692366fdf8941ded27c727e > by yourself because the SD card slot is not reachable? > Notice that to access that card slot you even have to remove the > nice blue ARM boilerplate. That's not my view. I have a mobile phone with an uSD card slot, but I have to take the cover off (and the battery) to access it. It doesn't mean I should not be able to use it from kernel side because of that, only that the designer of the phone (and of the Juno board + box by extension) did not expect people to use it with covers off all the time. I fail to see why you need to remove the SD card all the time. Surely opening the case once to put the uSD card in is enough? ;) > > The board is obviously designed to be reachable and the top part > of the case is obviously designed to be taken off by professional > users. I'm mostly on your side, Linus, I was just looking for more use cases. Like I've said, most of our customers seem to keep the case closed (or at least that is what they tell us :) ) so I'm looking for explanations on how you use the LEDs (visual debugging for big-LITTLE was how Lorenzo was using them on TC2 for example). Best regards, Liviu > > Yours, > Linus Walleij > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ?\_(?)_/?