| Message ID | 20230731215515.20682-1-laurent.pinchart@ideasonboard.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | ARM: dts: bcm2711-rpi-cm4-io: Add rtc on a pinctrl-muxed i2c bus | expand |
Hi Laurent On Mon, 31 Jul 2023 at 22:55, Laurent Pinchart <laurent.pinchart@ideasonboard.com> 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. 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. Dave > [1] https://lore.kernel.org/linux-arm-kernel/20211231115109.94626-1-uwe@kleine-koenig.org/ > > 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 >
Hi Dave, 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. > > [1] https://lore.kernel.org/linux-arm-kernel/20211231115109.94626-1-uwe@kleine-koenig.org/ > > > > 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(+)
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@kleine-koenig.org/ > > > > > > 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(+)
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. This I2C pin muxing is getting trickier than I initially thought :-S Naming the child buses i2c0_0 and i2c0_1 means that boards exposing I2C0 on the 40-pins GPIO headers would have different labels for that I2C0 interface depending on whether they multiplex I2C0 on other pins (e.g. on pins 44+45 for the camera connector of the Pi 4B) or not (e.g. the Pi 400). Overlays would thus not be compatible, which I suppose would be annoying for users. Before I send a new version of the series, I'd like to know what direction I should take. Is overlay compatibility between the two cases listed above important ? If so, I can imagine at least two solutions: - On boards that use I2C0 pinmuxing, we can rename the physical interface to i2c0if and name the two child buses i2c0 and i2c_csi_dsi. This is the solution used in the downstream kernel. It is implemented with a crude (in my opinion) hack though: board files have constructs such as #define i2c0 i2c0if #include "bcm2711.dtsi" #undef i2c0 - Always mux the I2C0 bus, on pins 0+1 and 28+29 or 0+1 and 44+45, depending on the board. Boards that don't connect anything to the I2C bus on pins 28+29 or 44+45 would still pick one of the two options. As there will be no I2C device on the second bus, the corresponding pinctrl entry will never be selected, so this should be harmless. The downside is that there will be an I2C mux instantiated in the kernel, adding a level of indirection to the I2C operations. Other solutions may be possible. What would be everybody's favourite option ? > > 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. > > > > [1] https://lore.kernel.org/linux-arm-kernel/20211231115109.94626-1-uwe@kleine-koenig.org/ > > > > > > 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(+)
Hi Laurent On Tue, 1 Aug 2023 at 21:33, Laurent Pinchart <laurent.pinchart@ideasonboard.com> wrote: > > 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). Really? The bindings [1] don't list it as required, and just trying it hasn't logged an error. The return value from of_property_read_u32 isn't checked at [2], so load remains unchanged at 7000 if not present. > 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 ? The relevant hardware person isn't in at present, but schematics for the RTC are on page 13 of the cm4io-datasheet [4]. Crystal is listed as a X32K768S300, and Farnell's copy of the datasheet [4] say that has a 6pF load capacitance. Dave [1] https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/rtc/nxp%2Cpcf85063.yaml [2] https://github.com/torvalds/linux/blob/master/drivers/rtc/rtc-pcf85063.c#L344 [3] https://datasheets.raspberrypi.com/cm4io/cm4io-datasheet.pdf [4] https://www.farnell.com/datasheets/1881558.pdf > > > > [1] https://lore.kernel.org/linux-arm-kernel/20211231115109.94626-1-uwe@kleine-koenig.org/ > > > > > > > > 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
Hi Dave, On Wed, Aug 02, 2023 at 11:20:32AM +0100, Dave Stevenson wrote: > On Tue, 1 Aug 2023 at 21:33, Laurent Pinchart wrote: > > 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). > > Really? The bindings [1] don't list it as required, and just trying it > hasn't logged an error. > The return value from of_property_read_u32 isn't checked at [2], so > load remains unchanged at 7000 if not present. My bad, I've misread the code and missed the initialization of the variable. > > 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 ? > > The relevant hardware person isn't in at present, but schematics for > the RTC are on page 13 of the cm4io-datasheet [4]. > Crystal is listed as a X32K768S300, and Farnell's copy of the > datasheet [4] say that has a 6pF load capacitance. That's what I found too :-) The default value of 7pF seems fine then. > [1] https://github.com/torvalds/linux/blob/master/Documentation/devicetree/bindings/rtc/nxp%2Cpcf85063.yaml > [2] https://github.com/torvalds/linux/blob/master/drivers/rtc/rtc-pcf85063.c#L344 > [3] https://datasheets.raspberrypi.com/cm4io/cm4io-datasheet.pdf > [4] https://www.farnell.com/datasheets/1881558.pdf > > > > > > [1] https://lore.kernel.org/linux-arm-kernel/20211231115109.94626-1-uwe@kleine-koenig.org/ > > > > > > > > > > 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(+)
Hi Laurent, Am 01.08.23 um 23:05 schrieb Laurent Pinchart: > 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. > > This I2C pin muxing is getting trickier than I initially thought :-S > Naming the child buses i2c0_0 and i2c0_1 means that boards exposing I2C0 > on the 40-pins GPIO headers would have different labels for that I2C0 > interface depending on whether they multiplex I2C0 on other pins (e.g. > on pins 44+45 for the camera connector of the Pi 4B) or not (e.g. the Pi > 400). Overlays would thus not be compatible, which I suppose would be > annoying for users. > > Before I send a new version of the series, I'd like to know what > direction I should take. Is overlay compatibility between the two cases > listed above important ? If so, I can imagine at least two solutions: > > - On boards that use I2C0 pinmuxing, we can rename the physical > interface to i2c0if and name the two child buses i2c0 and i2c_csi_dsi. > This is the solution used in the downstream kernel. It is implemented > with a crude (in my opinion) hack though: board files have constructs > such as > > #define i2c0 i2c0if > #include "bcm2711.dtsi" > #undef i2c0 > > - Always mux the I2C0 bus, on pins 0+1 and 28+29 or 0+1 and 44+45, > depending on the board. Boards that don't connect anything to the I2C > bus on pins 28+29 or 44+45 would still pick one of the two options. As > there will be no I2C device on the second bus, the corresponding > pinctrl entry will never be selected, so this should be harmless. The > downside is that there will be an I2C mux instantiated in the kernel, > adding a level of indirection to the I2C operations. > > Other solutions may be possible. > > What would be everybody's favourite option ? > sorry that you didn't get a reply to this question so far. Yesterday i tried to get my official rpi touchscreen running and noticed those many missing puzzle pieces (like this one) in Mainline. My gut feeling would tend to the second option. Best regards