From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Glass Date: Mon, 23 Feb 2015 08:30:54 -0700 Subject: [U-Boot] [PATCH 1/4] dm: gpio: extend gpio api by dm_gpio_set_pull() In-Reply-To: <54EB064E.7070800@samsung.com> 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: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de 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