From mboxrd@z Thu Jan 1 00:00:00 1970 From: Przemyslaw Marczak Date: Mon, 23 Feb 2015 17:56:43 +0100 Subject: [U-Boot] [PATCH 1/4] dm: gpio: extend gpio api by dm_gpio_set_pull() In-Reply-To: References: <1424178544-28632-1-git-send-email-p.marczak@samsung.com> <1424178544-28632-2-git-send-email-p.marczak@samsung.com> <54E4C02A.3030905@wwwdotorg.org> <54E5D2DC.1080508@samsung.com> <54E618CA.9000600@wwwdotorg.org> <54E6FFC2.1020508@samsung.com> <54E773C8.3090601@wwwdotorg.org> <54EB064E.7070800@samsung.com> Message-ID: <54EB5BCB.7010109@samsung.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hello, On 02/23/2015 04:30 PM, Simon Glass wrote: > Hi, > > On 23 February 2015 at 03:51, Przemyslaw Marczak wrote: >> >> Hello Simon, >> >> >> On 02/20/2015 08:29 PM, Simon Glass wrote: >>> >>> Hi, >>> >>> On 20 February 2015 at 10:50, Stephen Warren wrote: >>>> >>>> On 02/20/2015 02:34 AM, Przemyslaw Marczak wrote: >>>>> >>>>> >>>>> Hello, >>>>> >>>>> On 02/19/2015 06:09 PM, Stephen Warren wrote: >>>>>> >>>>>> >>>>>> On 02/19/2015 05:11 AM, Przemyslaw Marczak wrote: >>>>>>> >>>>>>> >>>>>>> Hello, >>>>>>> >>>>>>> On 02/18/2015 05:39 PM, Stephen Warren wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 02/17/2015 10:01 PM, Simon Glass wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> +Stephen who might have an opinion on this. >>>>>>>>> >>>>>>>>> Hi Przemyslaw, >>>>>>>>> >>>>>>>>> On 17 February 2015 at 06:09, Przemyslaw Marczak >>>>>>>>> wrote: >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> This commits extends: >>>>>>>>>> - dm gpio ops by: 'set_pull' call >>>>>>>>>> - dm gpio uclass by: dm_gpio_set_pull() function >>>>>>>>>> >>>>>>>>>> The pull mode is not defined so should be driver specific. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> It's good to implement this, but I think you should try to have a >>>>>>>>> standard interface. You could define the options you want to support >>>>>>>>> and pass in a standard value. >>>>>>>>> >>>>>>>>> Otherwise we are not really providing a driver abstraction, only an >>>>>>>>> interface. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> I don't think that pull is a GPIO-related function/property. At >>>>>>>> least on >>>>>>>> Tegra, the GPIO controller allows you to set the pin direction and the >>>>>>>> output value and that's it. Configuring pull-up/down and other IO >>>>>>>> related properties is done in the pinmux controller instead. I don't >>>>>>>> think we want a standard API that has to touch both HW modules at once. >>>>>>>> What common code needs to manipulate a GPIO's pull-up/down setting? As >>>>>>>> precedent observe that pull-up/down isn't part of the Linux kernel's >>>>>>>> GPIO API, but rather that's part of the SoC-specific pinctrl driver, >>>>>>>> which controls pinmuxing etc. >>>>>>>> >>>>>>> >>>>>>> This is a quite different than in the Exynos, where all the gpio >>>>>>> functions and properties can be set by few registers within range of >>>>>>> each gpio port base address. So in this case we don't touch another >>>>>>> hardware module, we modify one of available gpio related registers. >>>>>>> >>>>>>> Anyway, if we want to have a single and common gpio API in the future, >>>>>>> then I think it is better to add pull option. >>>>>> >>>>>> >>>>>> >>>>>> Why? I'll ask again: What common driver code needs to manipulate >>>>>> pull-ups? >>>>> >>>>> >>>>> >>>>> Please look at driver: drivers/gpio/s5p_gpio.c >>>>> >>>>> It's one driver related to one gpio hardware submodule and it takes care >>>>> about standard gpio properties and also mux/pull/drv/rate. >>>>> >>>>> And the exynos pinmux code is only a software abstraction: >>>>> arch/arm/cpu/armv7/exynos/pinmux.c >>>> >>>> >>>> >>>> I didn't want to ask which driver implements the control of pullups, but >>>> rather which other driver needs to turn pullups on/off in a standard way >>>> across multiple SoCs. >>>> >>>> In other words, do you expect code in common/ to need to call a "set pin >>>> pullup" function? If so, then we certainly need a standard API to manipulate >>>> pullups. However if no common code needs to manipulate pullups, then I'd >>>> argue we don't actually need a common API to do this, since there's no code >>>> that would call that common API. >>> >>> >>> We do currently use the GPIO to handle pullup/pulldown for some boards >>> so until we have a pinmux API (which might be a long while) it seems >>> reasonable for it to live there. >>> >>> If not, does anyone plan to write such an API? >>> >> >> Right, we uses this in most Exynos boards. But the boards uses direct calls to s5p gpio driver, without uclass. >> I wonder if wouldn't it be better and faster to leave the board low-level init routines as they are now. >> >> >>>> >>>> >>>>>> > And the driver will >>>>>>> >>>>>>> >>>>>>> implement what is required, instead of provide common and private api >>>>>>> for each driver. >>>>>> >>>>>> >>>>>> >>>>>> I'm not proposing driver-specific APIs, but rather having a common GPIO >>>>>> API and a common pinmux API. They need to be different since different >>>>>> HW modules may implement the functionality. >>>>>> >>>>> >>>>> As in the above example, for the Exynos it's the one hw module, so it's >>>>> simply. >>>>> >>>>>>> For the various devices it is unclear, what should be pinmux and what >>>>>>> should be gpio driver. >>>>>> >>>>>> >>>>>> >>>>>> How about the following are GPIO: >>>>>> * Set GPIO pin direction >>>>>> * Read GPIO input >>>>>> * Set GPIO output value >>>>>> >>>>>> ... and anything else is pinmux. That's the split in Linux and AFAIK it >>>>>> works out fine. >>>>>> >>>>>> It'd be perfectly fine for the same driver code to implement both a GPIO >>>>>> and a pinmux driver, if the HW supports it. >>>>>> >>>>> >>>>> Ok, I can drop this commit, since the current code works fine. >>>>> >>>>>>> Moreover in my opinion from the single external pin point of view the >>>>>>> pull up/down is the property of that pin. >>>>>> >>>>>> >>>>>> >>>>>> It's a property of the same pin, but semantically it's not manipulating >>>>>> a GPIO-related function. >>>>>> >>>>>>> Actually for Exynos, the pinmux is an abstraction and uses only GPIO >>>>>>> driver api in U-Boot. >>>>>>> >>>>>>> Do we need pinmux class? >>>>>>> >>>>>>> Best regards, >>>>>> >>>>>> >>>>>> >>>>>> >>>>> >>>>> As I wrote in one of my previous e-mail, I was testing eMMC detect. >>>>> And setting the pull was required for this, before call the pinmux for >>>>> eMMC pins. >>>>> But finally the eMMC detect seem to be not useful in case of the present >>>>> 'mmc rescan' command. >>>> >>>> >>>> >>>> Why wouldn't the pinmux driver for the whole system simply apply the board's >>>> whole pinmux configuration before initializing any IO controller drivers? IO >>>> controller drivers shouldn't have to initialize board-/SoC-specific pinmux, >>>> but the board-/SoC-specfic code should do so. >>>> >>>> At most, the eMMC driver should call a function such as pinmux_emmc(), and >>>> the board/SoC code should implement that as appropriate for that board. The >>>> eMMC driver shouldn't have to know about applying specific pullups/downs to >>>> specific pins (since those settings and pins are likely board-/SoC-specific, >>>> and drivers shouldn't know about board-/SoC-specific details). The only >>> >>> >>> No this way lies madness. It is how things work on Jetson and Nyan. >>> Loads of opaque tables and no idea what the pins are connected to. It >>> has some value for pins that U-Boot doesn't use (so we are just >>> setting them up for Linux) but even then it is really opaque. >>> >>> We can't even sent patches to the file because it is auto-generated >>> from a tool in another repo. Tiny differences between boards are >>> hidden because we repeat all the information again with just a line or >>> two of changes. I really don't want exynos to go that way. >>> >>>> exception would be if the standard IO protocol requires pullups to be >>>> changed during regular operation. In which case, a specific callback from >>>> the driver could be added for each protocol-mandated configuration change, >>>> thus keeping the IO controller driver still completely isolated from details >>>> of the pins and pinmux APIs etc. >>> >>> >>> This is like the 'funcmux' in Tegra I think. I think this is more >>> useful and we should use it to set up all peripheral pins. We can >>> review the code, see changes, understand what they relate to, etc. >>> >>> Anyway this all seems off-topic from this patch. >>> >>> Unless someone plans to write a pinmux subsystem for U-Boot (which I >>> agree would be better) I think the general approach of this patch is >>> good. >>> >>> Regards, >>> Simon >>> >> >> Ok, so there are two next versions of this patch-set. >> Please decide, which one is better. >> >> For me, at present, the current s5p_gpio api works fine for all the exynos based boards. >> Introducing the pinmux uclass is not a quick task, now I'm trying to focus on pmic. > > OK, then I think we should probably leave it as it is. If we add > pull-ups to driver model it should be done with pinctl as Stephen > says. I doubt this is a huge task, since we can likely port over the > code from Linux. But for now I think we should keep with the s5p API > until someone takes on pinctl. > > Regards, > Simon > Great, in this case, can the v3 be accepted? Best regards, -- Przemyslaw Marczak Samsung R&D Institute Poland Samsung Electronics p.marczak at samsung.com