On Tue, Jul 30, 2024 at 11:30:01AM GMT, Maxime Ripard wrote: > On Tue, Jul 30, 2024 at 11:46:24AM GMT, Dmitry Baryshkov wrote: > > On Tue, 30 Jul 2024 at 11:27, Maxime Ripard <mripard@xxxxxxxxxx> wrote: > > > > > > On Wed, Jul 24, 2024 at 07:59:21PM GMT, Marc Gonzalez wrote: > > > > On 15/07/2024 16:40, Maxime Ripard wrote: > > > > > On Thu, Jul 04, 2024 at 07:04:41PM GMT, Marc Gonzalez wrote: > > > > >> On 01/07/2024 15:50, Maxime Ripard wrote: > > > > >> > > > > >>> The i2c register access (and the whole behaviour of the device) is > > > > >>> constrained on the I2C_EN pin status, and you can't read it from the > > > > >>> device, so it's also something we need to have in the DT. > > > > >> > > > > >> I think the purpose of the I2C_EN pin might have been misunderstood. > > > > >> > > > > >> I2C_EN is not meant to be toggled, ever, by anyone from this planet. > > > > > > > > > > Toggled, probably not. Connected to a GPIO and the kernel has to assert > > > > > a level at boot, I've seen worse hardware design already. > > > > > > > > > >> I2C_EN is a layout-time setting, decided by a board manufacturer: > > > > >> > > > > >> - If the TDP158 is fully configured once-and-for-all at layout-time, > > > > >> then no I2C bus is required, and I2C_EN is pulled down forever. > > > > >> > > > > >> - If the board manufacturer wants to keep open the possibility > > > > >> to adjust some parameters at run-time, then they must connect > > > > >> the device to an I2C bus, and I2C_EN is pulled up forever. > > > > > > > > > > How do you express both cases in your current binding? > > > > > > > > It's not that I'm ignoring your question. > > > > > > > > It's that I don't understand what you're asking. > > > > > > And that's fine, you just need to say so. > > > > > > Generally speaking, you're focusing on the driver. The driver is not the > > > issue here. You can do whatever you want in the driver for all I care, > > > we can change that later on as we wish. > > > > > > The binding however cannot change, so it *has* to ideally cover all > > > possible situations the hardware can be used in, or at a minimum leave > > > the door open to support those without a compatibility breakage. > > > > > > That's why I've been asking those questions, because so far the only > > > thing you've claimed is that "I can't test the driver for anything > > > else", but, again, whether there's a driver or not, or if it's > > > functional, is completely missing the point. > > > > > > > SITUATION 1 > > > > tdp158 is pin strapped. > > > > Device node is child of root node. > > > > Properties in proposed binding are valid (regulators and power-on pin) > > > > Can be supported via module_platform_driver. > > > > > > > > SITUATION 2 > > > > tdp158 is sitting on I2C bus. > > > > Device node is child of i2c bus node. > > > > (robh said missing reg prop would be flagged by the compiler) > > > > Properties in proposed binding are valid (regulators and power-on pin) > > > > Supported via module_i2c_driver. > > > > > > > > If some settings-specific properties are added later, like skew, > > > > they would only be valid for the I2C programmable mode, obviously. > > > > > > I think there's a couple more combinations: > > > > > > - The device is connected on an I2C bus, but I2C_EN is tied low > > > > No, this is not possible. I2C pins are repurposed if I2C_EN is low. > > You can not call that an i2c bus anymore. > > > > > - The device is connected on an I2C bus, but I2C_EN is connected to a > > > GPIO and the kernel needs to assert its state at boot. > > > > This is a pretty strange configuration. The I2C_EN pin isn't supposed > > to be toggled dynamically. Anyway, if that happens, I'd use pinctrl / > > hog to control the pin. > > ACK. I still believe it would be valuable, but I don't really want to be > part of that conversation anymore. Marc, do whatever you want. Just to explain it, from my way of thinking the I2C_EN pin is the same as the address-strapping pins: they are usually hardwired by the device manufacturer. -- With best wishes Dmitry
