[PATCH 0/4] Add I2C support on TH1520

[Conor Dooley]

On Mon, Apr 29, 2024 at 03:07:55PM +0200, Thomas Bonnefille wrote:
> On 4/26/24 4:42 PM, Conor Dooley wrote:
> > On Fri, Apr 26, 2024 at 04:12:00PM +0200, Thomas Bonnefille wrote:
> > > On 4/25/24 6:35 PM, Conor Dooley wrote:
> > > > On Thu, Apr 25, 2024 at 09:51:26AM -0500, Rob Herring wrote:
> > > > > On Thu, 25 Apr 2024 10:21:31 +0200, Thomas Bonnefille wrote:

> > > > > New warnings running 'make CHECK_DTBS=y thead/th1520-beaglev-ahead.dtb' for 20240425082138.374445-1-thomas.bonnefille at bootlin.com:
> > > > > 
> > > > > arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dtb: i2c-clock: clock-frequency:0:0: 50000000 is greater than the maximum of 5000000
> > > > 
> > > > The bot is not freaking out here, 50 MHz is indeed more than 5 MHz :)
> > > 
> > > 5MHz is the maximum clock-frequency, ie. the I2C bus frequency.
> > > This is actually set to 100kHz for I2C0 in the DT:
> > > 
> > > &i2c0 {
> > >      status = "okay";
> > >      clock-frequency = <100000>; <----
> > > ...
> > > };
> > > 
> > > 50MHz is the "fixed-clock" frequency, that is the clock feeding the I2C
> > > IP block:
> > > 
> > > i2c_ic_clk: i2c-clock {
> > >      compatible = "fixed-clock";
> > >      clock-frequency = <50000000>; <-----
> > >      #clock-cells = <0>;
> > > };
> > > 
> > > My guess is that the bot confused the clock-frequency parameter for the bus
> > > clock (SCL) with the i2c-ic-clock value for the controller itself during the
> > > checks.
> > > 
> > > Do you agree with this or am I misunderstanding the error ?
> > > 
> > > If I lower the fixed-clock frequency to eg. 100kHz, the error is gone. But I
> > > guess the 5MHz limit should probably not apply to the input clock?
> > 
> > Heh, I know why that's happening - it's your node name.
> > The pattern for i2c controllers is "^i2c(@.*)?":
> > https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/i2c/i2c-controller.yaml
> > 
> > Rob co-incidentally (or maybe not) put out a patch for fixed-frequency
> > clock names, suggesting using clock as a prefix:
> > https://lore.kernel.org/all/20240425183810.3079069-1-robh@kernel.org/
> > If we switched to that format, I believe your problem goes away.

> Indeed it was the node name, when I switched the name of the fixed clock to
> clock-i2c-ic, the error was gone, thank you. :)
> But i2c_ic_clk shouldn't match "^i2c(@.*)?", one of my teammates suggested

The pattern in i2c-controller.yaml is only applied to nodenames, the label
(which is what i2c_ic_clk is) doesn't matter and could be left as-is.

> that the error may instead come from this line
> https://elixir.bootlin.com/linux/latest/source/scripts/dtc/checks.c#L1023.
> 
> But as Drew is working on new iterations of the TH1520's clock driver I will
> just delete this fixed clock and publish a second version depending on his
> patch.

Sure, but you may be waiting a while for that to land :)

Cheers,
Conor.
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