On Mon, Dec 23, 2019 at 4:11 AM Hanks Chen <hanks.chen@xxxxxxxxxxxx> wrote: > On Fri, 2019-08-23 at 10:57 +0200, Linus Walleij wrote: > > On Mon, Aug 19, 2019 at 11:22 AM Mars Cheng <mars.cheng@xxxxxxxxxxxx> wrote: > > This does not explain what a "virtual GPIO" is in this > > context, so please elaborate. What is this? Why does > > it exist? What is it used for? > > > > GPIO is "general purpose input/output" and it is a > > pretty rubbery category already as it is, so we need > > to define our terms pretty strictly. > > > Virtual GPIO only used inside SOC and not being exported to outside SOC > in MTK platform. Some modules use virtual GPIO as eint (e.g. pmic or > usb). I would call that internal GPIOs, those are very real rails inside the chip made with polysilicone so there is nothing "virtual" about them. If the documentation for the chip calls them virtual then explain in the driver that these are SoC-internal lines so that everyone will get it. Is the PMIC inside the SoC? I thought that was usually outside of it in its own chip. But I suppose there could be some interface to it in the SoC and then that interface has this EINT? > In MTK platform, external interrupt (EINT) and GPIO is 1-1 mapping and > we can set GPIO as eint. > But some modules use specific eint which doesn't have real GPIO pin. > So we use virtual GPIO to map it. OK I get it I think... just put these comments into the code as well so we understand when reading the code what is going on. > > > + if (mtk_is_virt_gpio(hw, gpio)) > > > + return 1; > > > > Why are "virtual GPIOs" always inputs? > > We set virtual GPIO as eint. > It mean virtual GPIO only used inside SOC and not being exported to > outside SOC. Are you saying that: - "Virtual" GPIOs are always and only used for interrupts - Since they are only used for interrupts, they are always inputs Then write that in a comment to the above change so we know this context. Yours, Linus Walleij
