Hi Dave, On Tue, Aug 01, 2023 at 05:43:15PM +0300, Laurent Pinchart wrote: > On Tue, Aug 01, 2023 at 03:22:17PM +0100, Dave Stevenson wrote: > > On Mon, 31 Jul 2023 at 22:55, Laurent Pinchart wrote: > > > > > > Hello, > > > > > > This series is an attempt to revive support for pinmuxed I2C0 on the > > > Raspberry Pi BCM2711-based board. > > > > > > On BCM2711-based boards, the I2C0 controller can be muxed between pins > > > 0+1 or 44+45. The former is exposed through the 40-pins GPIO connector, > > > and the latter is used for the RTC on the CM4 I/O board, but also routed > > > to the display and camera connectors on the Raspberry Pi 4B board. The > > > other BCM2711-based board, the Raspberry Pi 400, does not expose or > > > connect anything to pins 44+45. > > > > > > A previous version was posted ([1]) a year and a half ago by Uwe. It > > > bundled the pinmuxing and RTC in a single patch, with the mux added to > > > the CM4 I/O board device tree. This version splits this in two, and > > > moves the pinumxing to the bcm2711-rpi.dtsi to also support the > > > Raspberry Pi 4B. > > > > > > The Raspberry Pi downstream kernel has a more complex DT architecture in > > > order to support different I2C0 pinmuxing for other boards. Two files, > > > bcm283x-rpi-i2c0mux_0_28.dtsi and bcm283x-rpi-i2c0mux_0_44.dtsi, define > > > the two I2C0 pinxmuxing options (pins 0+1 and 28+29, or pins 0+1 and > > > 44+45). Each board .dts then includes the appropriate file. I'm hoping > > > to avoid this additional complexity for now, by addressing the I2C0 > > > pinmuxing for BCM2711-based boards only. If/when support for I2C0 > > > pinmuxing on boards will be needed, we can revisit this topic. > > > > > > Compared to the Raspberry Pi downstream kernel, the two muxed I2C buses > > > are labelled i2c0_0 and i2c0_1 instead of i2c0 and i2c_csi_dsi. This > > > change was made to keep the naming of the I2C controller labels > > > consistent, avoiding renaming of the I2C0 controller's label from i2c0 > > > to i2c0if. > > > > > > Dave, are you fine with the differences between this patch series and > > > the downstream kernel, or do you expect them to cause issues ? > > > > I've checked with Phil. There's nothing too untoward that will cause > > us any significant grief. > > Thanks for checking. > > In the meantime, I realized that the CM4S is 2711-based and, according > to the downstream DT, multiplexes I2C0 on pins 28+29, not 44+45 :-( > Umang and Kieran also told me that we want to test camera support on the > Pi 3B. It looks like the only viable approach to support all that will > be to include per-board I2C0 pinmux .dtsi as done in the downstream > kernel. I'll send a v5. > > > Phil has commented that the RTC is an PCF85063AT, so that compatible > > string should be "nxp,pcf85063a" if you actually want to make use of > > the alarm output. > > Then again the driver support for the alarm output appears to want it > > routed to an IRQ rather than as a system reset/wakeup, so it probably > > makes little difference. It llargely depends on how exact you want to > > be in your hardware description. > > I'll update the compatible string, it's an easy change and it's nice to > be accurate. The driver will print a warning if the quartz-load-femtofarads property isn't set in DT (it can be either 7pF or 12.5pF). If I'm not mistaken, the quartz oscillator on the CM4 I/O board is calibrated for a 6pF load capacitance, so 7pF is the closest and best value. Could you confirm that ? > > > [1] https://lore.kernel.org/linux-arm-kernel/20211231115109.94626-1-uwe@xxxxxxxxxxxxxxxxx/ > > > > > > Uwe Kleine-König (2): > > > ARM: dts: bcm2711-rpi: Add pinctrl-based multiplexing for I2C0 > > > ARM: dts: bcm2711-rpi-cm4-io: Add RTC on I2C0 > > > > > > arch/arm/boot/dts/bcm2711-rpi-cm4-io.dts | 16 ++++++++++++ > > > arch/arm/boot/dts/bcm2711-rpi.dtsi | 31 ++++++++++++++++++++++++ > > > 2 files changed, 47 insertions(+) -- Regards, Laurent Pinchart
