On Mon, Jun 11, 2018 at 11:46 AM Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx> wrote: > On 06/05/2018 04:49 PM, Linus Walleij wrote: > > The Atmel ECC driver contains a check for the I2C bus clock > > frequency, so as to check that the I2C adapter in use > > satisfies the device specs. > > > > If the device is connected to a device tree node that does not > > contain a clock frequency setting, such as an I2C mux or gate, > > this blocks the probe. Make the probe continue silently if > > no clock frequency can be found, assuming all is safe. > > I don't think it's safe. We use bus_clk_rate to compute the ecc508's > wake token. If you can't wake the device, it will ignore all your > commands. I see. I wonder why it works so well for me then? Could we just print a warning and continue? The general advice for the kernel is not to bail out if hardware is not optimally configured, but continue with a warning that maybe not everything is all right. > My proposal was to introduce a bus_freq_hz member in the i2c_adapter > structure (https://patchwork.kernel.org/patch/10307637/), but I haven't > received feedback yet, Wolfram? > > I would say first to check the bus_freq_hz from adapter (if it will be > accepted) else to look into dt and, in the last case, if nowhere > provided, to block the probe. So blocking the probe because we are not 100% sure the hardware will work is against established practice: the established practice is to be liberal with letting probe() continue, but emit a warning. In my case that is good because it makes the hardware probe and work without any visible problems. I *can* try to traverse the device tree upwards from the mux node to find the parent I2C controller and its "clock-frequency" property. I felt that was hackish, but if you prefer the hack I can try to use that. Yours, Linus Walleij
