[DISCLAIMER : both of us (Alessandro and Davide) are not devicetree experts, so please understand how our issues and our dislike of the approach may result from some lack of knowledge. (any pointer is welcome).] As some of you may remember, we're submitting patches adding support for the STA2X11 (aka Connext) ST chip. The device is a pci-express I/O HUB containing a number of AMBA peripherals (gpios, uarts, mmc/sd, dma, ST msps, spi, i2c). Being a PCI device, it's fully autoprobed: we can even plug two evaluation boards in the same PC, and all devices in there are expected to work (and they do, with some of our patch-sets). A first set of drivers for this chip was written by Wind River, by simply copying AMBA drivers and turning them into pci drivers. This of course worked, but implied tons of duplicated code. Our attempt was to recycle existing AMBA drivers by instantiating AMBA devices at runtime. This was done by a rather simple pci to amba "bridge" module, submitted several times, up to https://lkml.org/lkml/2013/2/20/698 The problem was that AMBA devices need platform data with some instance information. Platform code (under arch/x86/sta2x11/) was submitted for some Connext based boards, but it was rejected as "ARM shit" by Peter Anvin (https://lkml.org/lkml/2012/5/28/266). We agree the tables are not beautiful, so we didn't submit such stuff any more. Peter suggested that "the firmware should provide ACPI tables", but this is not possible for plug-in pci boards, or we should use devicetree (Peter's message: https://lkml.org/lkml/2012/5/29/38). So we turned to devicetree, mostly because AMBA drivers usually already have devicetree support. Davide took over the effort, which turned out to be really big. Some of the problems he found are: * Passing a dtb to the kernel: we use a modified kexec at present because x86 boot loaders can't pass the DT blob, to our knowledge. * Passing correct irq numbers to the AMBA drivers, because PCI MSI irq numbers are dynamically allocated (we solved this by using of_update_property() at runtime). We also had to register a new irq domain for msi irqs, otherwise of_irq_map_one() would complain about irqs lacking a corresponding domain. * Switching to a new gpio driver with devicetree support (we took the Nomadik gpio/pinctrl because our device apparently has more or less the same gpio cell as the Nomadik chip). This requires implementation of writel_relaxed() and IRQF_VALID on x86: we hacked them internally but the patches are not part of this set. We're willing to solve these incompatibilities first, if there's interest. * Writing a suitable dts: at present, a dts only exists for one of the STA2X11 based boards (Intel Northville). This includes a copy of all the physical addresses for the devices, as dts requires that, even if such addresses are automatically assigned by PCI. Clearly, with this approach we kill PCI autodetect: if you plug to a different slot you need a different dts. This got us a more or less working kernel on the Northville board (where the device is soldered on the motherboard and acts as main chipset). The plug-in PCIe board cannot be supported by device tree, as far as we know, which in our opinion is a strong downside of device tree in favor of the platform data "shit". Here's the list of amba devices after boot (we used a kernel with a common clock framework implementation for the Connext, patches to be (re)submitted shortly): [root@localhost ~]# for d in `ls /sys/bus/amba/devices/` ; \ do cat /sys/bus/amba/devices/$d/id ; done 00280080 # -> amba pl080 00380802 # -> amba pl011 00380802 # -> amba pl011 00380802 # -> amba pl011 00380802 # -> amba pl011 10480180 # -> amba mmci 10480180 # -> amba mmci 10480180 # -> amba mmci 10480180 # -> amba mmci 00080023 # -> amba pl023 00080023 # -> amba pl023 00080023 # -> amba pl023 00280080 # -> amba pl080 And the platform devices: [root@localhost ~]# for d in `ls /sys/bus/platform/devices/` ; \ do cat /sys/bus/platform/devices/$d/modalias ; done platform:alarmtimer platform:apb-regs.3 # Connext apb-regs platform:apb-soc-regs.3 # Connext apb-soc-regs platform:gpio-0000:03:00.0-0 # Connext gpios 0..3 platform:gpio-0000:03:00.0-1 platform:gpio-0000:03:00.0-2 platform:gpio-0000:03:00.0-3 platform:microcode platform:mmio-0000:05:00.5-0 # Connext esram memory platform:pcspkr platform:regulatory platform:scr.3 # Connext scr (OTP) platform:sctl.3 # Connext sysctl platform:serial8250 platform:sta2x11-clock-regs # Connext virtual clock regs platform dev But this awful pile of dts data will not work for he pluggable PCIe card. We need to regenerate the dts file at each and every boot, because PCI assignment may change according to what other cards are present. So this devicetree stuff is killing all the autodetection of PCI, and is very difficult to pass over in the x86 world. On the other hand platform data is denied by x86 maintainers. So the question is: what is the right way (and the right dts structure) to deal with a hotplug bus that instantiates AMBA devices, without killing del self-detection features? Thanks /alessandro Alessandro Rubini (5): x86: fix warning for sta2x11 DMA: PL330: use prefix in reg names to build under x86 mmc: Use the new <linux/sizes.h> x86: add CONFIG_ARM_AMBA, selected by STA2X11 drivers/amba: add support for a PCI bridge Davide Ciminaghi (21): x86 STA2X11: select devicetree related config items. OF platform: export of_amba_device_create() OF platform, of_amba_device_create(): add parent resource to parameters. kernel irqdomain: export irq_domain_disassociate() x86 devicetree: add irq domain for msi irqs x86 devicetree: add functions for handling setup/teardown of MSI irqs x86 kernel apic: notify MSI irqdomain(s) on setup/teardown of MSI IRQs drivers/amba/pci-amba.c: use devicetree for amba device creation. gpio: remove sta2x11-gpio x86 STA2X11: remove the sta2x11-mfd driver. x86 STA2X11 platform: add sta2x11_platform_init() x86 STA2X11 platform: add sta2x11_instance_data helpers x86 STA2X11 platform: add a common probe function for platform devices x86 STA2X11 platform: create sta2x11-clock-regs device x86 STA2X11 platform: remove useless pr_info()'s AMBA: pci-amba bridge: improve code readability AMBA: pci-amba bridge: extend number of amba devs per pci device AMBA: pci-amba bridge: export function creating pci-amba device names x86 STA2X11: add dts for Intel's Northville board drivers/clk: sta2x11 common clock framework implementation pinctrl: add support for sta2x11 (via pinctrl-nomadik) .../devicetree/bindings/pinctrl/ste,nomadik.txt | 2 +- .../devicetree/bindings/x86/interrupt.txt | 14 + arch/x86/Kconfig | 10 + arch/x86/include/asm/prom.h | 9 + arch/x86/include/asm/sta2x11.h | 358 ++++++++- arch/x86/kernel/apic/io_apic.c | 5 + arch/x86/kernel/devicetree.c | 60 ++ arch/x86/pci/sta2x11-fixup.c | 9 +- arch/x86/platform/Makefile | 1 + arch/x86/platform/sta2x11/Makefile | 1 + arch/x86/platform/sta2x11/northville.dts | 941 ++++++++++++++++++++ arch/x86/platform/sta2x11/sta2x11.c | 522 +++++++++++ drivers/Kconfig | 2 + drivers/amba/Kconfig | 10 + drivers/amba/Makefile | 1 + drivers/amba/pci-amba.c | 298 +++++++ drivers/clk/Makefile | 1 + drivers/clk/sta2x11/Makefile | 1 + drivers/clk/sta2x11/clk-audio-pll.c | 149 +++ drivers/clk/sta2x11/clk-soc-pll.c | 95 ++ drivers/clk/sta2x11/clk.c | 865 ++++++++++++++++++ drivers/clk/sta2x11/clk.h | 88 ++ drivers/dma/pl330.c | 107 ++-- drivers/gpio/Kconfig | 8 - drivers/gpio/Makefile | 1 - drivers/gpio/gpio-sta2x11.c | 440 --------- drivers/mfd/Kconfig | 6 - drivers/mfd/Makefile | 1 - drivers/mfd/sta2x11-mfd.c | 680 -------------- drivers/mmc/host/mmci.c | 2 +- drivers/mmc/host/msm_sdcc.c | 2 +- drivers/mmc/host/mvsdio.c | 2 +- drivers/mmc/host/pxamci.c | 3 +- drivers/of/platform.c | 24 +- drivers/pinctrl/Kconfig | 6 +- drivers/pinctrl/Makefile | 1 + drivers/pinctrl/pinctrl-nomadik-sta2x11.c | 578 ++++++++++++ drivers/pinctrl/pinctrl-nomadik.c | 7 + drivers/pinctrl/pinctrl-nomadik.h | 14 + include/linux/irqdomain.h | 3 + include/linux/mfd/sta2x11-mfd.h | 518 ----------- include/linux/of_platform.h | 7 +- include/linux/pci-amba.h | 42 + kernel/irq/irqdomain.c | 3 +- 44 files changed, 4167 insertions(+), 1730 deletions(-) create mode 100644 arch/x86/platform/sta2x11/Makefile create mode 100644 arch/x86/platform/sta2x11/northville.dts create mode 100644 arch/x86/platform/sta2x11/sta2x11.c create mode 100644 drivers/amba/Kconfig create mode 100644 drivers/amba/pci-amba.c create mode 100644 drivers/clk/sta2x11/Makefile create mode 100644 drivers/clk/sta2x11/clk-audio-pll.c create mode 100644 drivers/clk/sta2x11/clk-soc-pll.c create mode 100644 drivers/clk/sta2x11/clk.c create mode 100644 drivers/clk/sta2x11/clk.h delete mode 100644 drivers/gpio/gpio-sta2x11.c delete mode 100644 drivers/mfd/sta2x11-mfd.c create mode 100644 drivers/pinctrl/pinctrl-nomadik-sta2x11.c delete mode 100644 include/linux/mfd/sta2x11-mfd.h create mode 100644 include/linux/pci-amba.h -- 1.7.7.2 -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
