On 12 November 2011 19:47, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > On Sat, Nov 12, 2011 at 12:22 PM, Thomas Abraham > <thomas.abraham@xxxxxxxxxx> wrote: > >> Samsung SoC's use two pin functions out of 4/8/16 pin functions to >> represent that a pin is used as a gpio. For instance, function 0 means >> pin is used as a gpio input, and function 1 means pin is used as gpio >> output. A pin cannot support both input and output mode at the same >> time. >> >> The existing pinmux_[request|free]_gpio() functions can specify that a >> pin has to be set in gpio function mode, but lack the provision to >> select input or output mode for the gpio. > > OK then this needs fixing if this API is to persist. > >> The alternative approach of >> using pin functions to select gpio-input or gpio-output will be used >> for samsung pinmux drivers. >> >> This means the gpio_direction_[input|output] api's would remain unused >> on samsung platforms. And existing platforms already using this api >> will have to be modified to use the pinmux api to select the direction >> of the gpio pin. And the role of gpio_request will seem redundant when >> used along with pinmux_get(). > > This does not seem right. Why should it not use > gpio_direction_[input|output] to select whether the pin is used > for input or output like everyone else? The gpio_direction_[input|output]() internally sets the pin function (by writing to pin function register) to either gpio input|output. Since the gpio calls should stop writing to the pin function registers (since we have pinmux driver now), there should be way for gpio_direction_[input|output]() to inform pinmux driver to set gpio in input|output mode. But this cannot be achieved with existing pinctrl/pinmux api and so gpio_direction_[input|output]() will not be used and separate pin function for gpio input/output setup and used in the pinmux driver. > > This will just lead to trouble with shared HW blocks where > one use gpio_direction_[input|output] to select the direction > while another one will use some pinctrl API. Yes, that is true. So gpio_direction_[input|output]() would not be used to setup the gpio direction anymore. > > We need one of two things: > > 1. pinmux_[request|free]_gpio() to pass direction to the > core and driver, or This approach seems to be better. > > 2. A use pattern like this: > pmx = pinmux_get(dev, "gpio-1-in"); > /* Use as input */ > pinmux_put(pmx); > pmx = pinmux_get(dev, "gpio-1-out"); > /* Use as output */ > etc > > The latter seems hopeless to maintain. So the external call > pinmux_[request|free]_gpio() needs to be kept around, > and it needs to be called *internally* by GPIO drivers to set > up pins, so as to avoid hazzle. > > In my opinion atleast... Yes. I agree with that. > > Linus Walleij > Thank you LinusW. Regards, Thomas. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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