From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Nelson Date: Sat, 2 Apr 2016 08:13:55 -0700 Subject: [U-Boot] [PATCH] dm: gpio: handle GPIO_ACTIVE_LOW flag in DT In-Reply-To: <20160402054612.GA27255@linux-7smt.suse> References: <1458936731-13223-1-git-send-email-eric@nelint.com> <20160329045729.GA32493@linux-7smt.suse> <56FD8B60.8060103@nelint.com> <20160402054612.GA27255@linux-7smt.suse> Message-ID: <56FFE1B3.6070608@nelint.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Peng, On 04/01/2016 10:46 PM, Peng Fan wrote: > On Thu, Mar 31, 2016 at 01:41:04PM -0700, Eric Nelson wrote: >> On 03/28/2016 09:57 PM, Peng Fan wrote: >>> On Fri, Mar 25, 2016 at 01:12:11PM -0700, Eric Nelson wrote: >>>> Device tree parsing of GPIO nodes is currently ignoring flags. >>>> >>>> Add support for GPIO_ACTIVE_LOW by checking for the presence >>>> of the flag and setting the desc->flags field to the driver >>>> model constant GPIOD_ACTIVE_LOW. >>> >>> You may need to try this: https://patchwork.ozlabs.org/patch/597363/ >>> >> Thanks for pointing this out. >> >> This patch also works, but it has me confused. >> >> How/why is parsing the ACTIVE_LOW flag specific to MXC? >> >> This is a general-purpose flag in the kernel, not something machine- >> specific. >> >> It also appears that there are a bunch of other copies >> of this same bit of code in the various mach_xlate() routines: >> >> desc->flags = args->args[1] & GPIO_ACTIVE_LOW ? GPIOD_ACTIVE_LOW : 0; >> >> If it's done in gpio-uclass, this isn't needed and xlate can >> be removed from mxc-gpio and quite a few other architectures. >> >> Please advise, > > I saw you have posted a patch set to convert other gpio drivers. > But actually the translation of gpio property should be done by > each gpio driver. Alought we have gpio-cells=<2> for most gpio > drivers, but if there is one case that gpio-cells=<3>, and it have > different meaning for each cell from other most drivers? > Which case has gpio-cells=<3>? As far as I can tell, only tegra and sandbox have something other than parsing of offset and the GPIO_ACTIVE_LOW flag. Tegra seems to have gpio-cells=<2> and sandbox has either 0 or 1. > So I suggest we follow the linux way, > > 434 if (!chip->of_xlate) { > 435 chip->of_gpio_n_cells = 2; > 436 chip->of_xlate = of_gpio_simple_xlate; > 437 } > > If gpio drivers does not provide xlate function, then use a simple xlate > function. If gpio drivers have their own xlate function, then use their > own way. > The recommendation in device-tree-bindings/gpio/gpio.txt is to have the GPIO_ACTIVE_LOW/HIGH flag in the second cell, so parsing that directly in gpio_find_and_xlate() seems right. That way, driver-specific parsing only needs to handle additional flags or needs as is the case with tegra. > Also I do no think delete the xlate implementation is not a good idea. > Which xlate routine? All of those that my patch set removes? Since none of them do anything besides parsing the offset and GPIO_ACTIVE_LOW flag, this seems like code bloat. Please advise, Eric