On Wed, Sep 07, 2022 at 12:09:01AM +0200, Pali Rohár wrote: > On Tuesday 06 September 2022 14:52:42 Dmitry Torokhov wrote: > > On Tue, Sep 06, 2022 at 11:41:14PM +0200, Pali Rohár wrote: > > > On Tuesday 06 September 2022 14:26:32 Dmitry Torokhov wrote: > > > would not be such easy as during startup we need to reset endpoint card. > > > Normally just putting it from reset, but if card was not reset state > > > prior probing driver then it is needed to first put it into reset... > > > > > > I would fix it this issue after your patch is merged to prevent any > > > other merge conflicts. > > > > > > How to tell devm_fwnode_gpiod_get() function that caller is not > > > interested in changing signal line? Just by changing GPIOD_OUT_HIGH to 0? > > > > I think there are 2 options: > > > > 1. Start with GPIOD_OUT_LOW (i.e. reset is explicitly deasserted), and > > then in powerup/powerdown you do explicit on/off transitions with proper > > timings. > > PERST# is active-low. So deasserting means to put it into high state. > But device tree can specify if line is active-high as on some board > designs is GPIO output connected to inverter (or to level shifter with > additional logic of signal inversion). So what [GPIOD_]OUT_LOW means in > this context? Just it is needed that from driver point of view always > value 1 means reset active and 0 means reset inactive, independently of > double (triple?) inversions. Think of GPIOD_OUT_LOW and GPIOD_OUT_HIGH as logical off and on, or logical deactivate/activate. Gpiolib will take into account declared polarity of the line when it drives the output, so for lines marked as GPIO_ACTIVE_HIGH GPIO_OUT_HIGH will result in line driven HIGH, whereas for lines marked as GPIO_ACTIVE_LOW GPIO_OUT_HIGH will result in the line being driven LOW. Linus, do you think we should introduce GPIOD_OUT_INACTIVE / GPIOD_OUT_ACTIVE or GPIOD_OUT_DEASSERTED / GPIOD_OUT_ASSERTED and deprecate existing GPIOD_OUT_LOW and GPIO_OUT_HIGH? Thanks. -- Dmitry
