Messages in this thread | | | Subject | Re: fw_devlink on will break all snps,dw-apb-gpio users | From | Robin Murphy <> | Date | Thu, 15 Oct 2020 15:08:33 +0100 |
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On 2020-10-15 10:52, Jisheng Zhang wrote: > On Thu, 15 Oct 2020 01:48:13 -0700 > Saravana Kannan <saravanak@google.com> wrote: > >> On Thu, Oct 15, 2020 at 1:15 AM Jisheng Zhang >> <Jisheng.Zhang@synaptics.com> wrote: >>> >>> On Wed, 14 Oct 2020 22:04:24 -0700 Saravana Kannan wrote: >>> >>>> >>>> >>>> On Wed, Oct 14, 2020 at 9:02 PM Jisheng Zhang >>>> <Jisheng.Zhang@synaptics.com> wrote: >>>>> >>>>> On Wed, 14 Oct 2020 10:29:36 -0700 >>>>> Saravana Kannan <saravanak@google.com> wrote: >>>>> >>>>>> >>>>>> >>>>>> On Wed, Oct 14, 2020 at 4:12 AM Jisheng Zhang >>>>>> <Jisheng.Zhang@synaptics.com> wrote: >>>>>>> >>>>>>> Hi, >>>>>>> >>>>>>> If set fw_devlink as on, any consumers of dw apb gpio won't probe. >>>>>>> >>>>>>> The related dts looks like: >>>>>>> >>>>>>> gpio0: gpio@2400 { >>>>>>> compatible = "snps,dw-apb-gpio"; >>>>>>> #address-cells = <1>; >>>>>>> #size-cells = <0>; >>>>>>> >>>>>>> porta: gpio-port@0 { >>>>>>> compatible = "snps,dw-apb-gpio-port"; >>>>>>> gpio-controller; >>>>>>> #gpio-cells = <2>; >>>>>>> ngpios = <32>; >>>>>>> reg = <0>; >>>>>>> }; >>>>>>> }; >>>>>>> >>>>>>> device_foo { >>>>>>> status = "okay" >>>>>>> ...; >>>>>>> reset-gpio = <&porta, 0, GPIO_ACTIVE_HIGH>; >>>>>>> }; >>>>>>> >>>>>>> If I change the reset-gpio property to use another kind of gpio phandle, >>>>>>> e.g gpio expander, then device_foo can be probed successfully. >>>>>>> >>>>>>> The gpio expander dt node looks like: >>>>>>> >>>>>>> expander3: gpio@44 { >>>>>>> compatible = "fcs,fxl6408"; >>>>>>> pinctrl-names = "default"; >>>>>>> pinctrl-0 = <&expander3_pmux>; >>>>>>> reg = <0x44>; >>>>>>> gpio-controller; >>>>>>> #gpio-cells = <2>; >>>>>>> interrupt-parent = <&portb>; >>>>>>> interrupts = <23 IRQ_TYPE_NONE>; >>>>>>> interrupt-controller; >>>>>>> #interrupt-cells = <2>; >>>>>>> }; >>>>>>> >>>>>>> The common pattern looks like the devlink can't cope with suppliers from >>>>>>> child dt node. >>>>>> >>>>>> fw_devlink doesn't have any problem dealing with child devices being >>>>>> suppliers. The problem with your case is that the >>>>>> drivers/gpio/gpio-dwapb.c driver directly parses the child nodes and >>>>>> never creates struct devices for them. If you have a node with >>>>>> compatible string, fw_devlink expects you to create and probe a struct >>>>>> device for it. So change your driver to add the child devices as >>>>>> devices instead of just parsing the node directly and doing stuff with >>>>>> it. >>>>>> >>>>>> Either that, or stop putting "compatible" string in a node if you >>>>>> don't plan to actually treat it as a device -- but that's too late for >>>>>> this driver (it needs to be backward compatible). So change the driver >>>>>> to add of_platform_populate() and write a driver that probes >>>>>> "snps,dw-apb-gpio-port". >>>>>> >>>>> >>>>> Thanks for the information. The "snps,dw-apb-gpio-port" is never used, >>>>> so I just sent out a series to remove it. >>>> >>>> I'd actually prefer that you fix the kernel code to actually use it. >>>> So that fw_devlink can be backward compatible (Older DT + new kernel). >>>> The change is pretty trivial (I just have time to do it for you). >>>> >>> >>> I agree the change is trivial, but it will add some useless LoCs like below. >> >> It's not useless if it preserves backward compatibility with DT. >> >>> I'm not sure whether this is acceptable.So add GPIO and DT maintainers to comment. >>> >>> Hi Linus, Rob, >>> >>> Could you please comment? A simple introduction of the problem: >>> >>> As pointed out by Saravana, "gpio-dwapb.c driver directly parses the child >>> nodes and never creates struct devices for them. If you have a node with >>> compatible string, fw_devlink expects you to create and probe a struct >>> device for it", so once we set fw_devlink=on, then any users of gpio-dwapb >>> as below won't be probed. >>> >>> device_foo { >>> status = "okay" >>> ...; >>> reset-gpio = <&porta, 0, GPIO_ACTIVE_HIGH>; >>> }; >>> >>> The compatible string "snps,dw-apb-gpio-port" is never used, but it's in >>> the dt-binding since the dw gpio mainlined. I believe the every dw apb >>> users just copy the compatible string in to soc dtsi. So I submit a series >>> to remove the unused "snps,dw-apb-gpio-port" https://lkml.org/lkml/2020/10/14/1186 >>> But this will break Older DT + new kernel with fw_devlink on. Which solution >>> is better? >>> >>> If the following patch is acceptable, I can submit it once 5.10-rc1 is out. >>> >>> thanks >>> >>> diff --git a/drivers/gpio/gpio-dwapb.c b/drivers/gpio/gpio-dwapb.c >>> index 1d8d55bd63aa..b8e012e48b59 100644 >>> --- a/drivers/gpio/gpio-dwapb.c >>> +++ b/drivers/gpio/gpio-dwapb.c >>> @@ -19,6 +19,7 @@ >>> #include <linux/of_address.h> >>> #include <linux/of_device.h> >>> #include <linux/of_irq.h> >>> +#include <linux/of_platform.h> >>> #include <linux/platform_device.h> >>> #include <linux/property.h> >>> #include <linux/reset.h> >>> @@ -694,6 +695,10 @@ static int dwapb_gpio_probe(struct platform_device *pdev) >>> } >>> platform_set_drvdata(pdev, gpio); >>> >>> + err = devm_of_platform_populate(dev); >>> + if (err) >>> + goto out_unregister; >>> + >>> return 0; >>> >>> out_unregister: >>> @@ -820,6 +825,25 @@ static struct platform_driver dwapb_gpio_driver = { >>> >>> module_platform_driver(dwapb_gpio_driver); >>> >>> +static const struct of_device_id dwapb_port_of_match[] = { >>> + { .compatible = "snps,dw-apb-gpio-port" }, >>> + { /* Sentinel */ } >>> +}; >>> + >>> +static int dwapb_gpio_port_probe(struct platform_device *pdev) >>> +{ >>> + return 0; >> >> No, I'm not asking to do a stub/dummy probe. Move the stuff you do >> inside device_for_each_child_node{} and dwapb_gpio_add_port() into >> this probe function. Those two pieces of code together are effectively >> "probing" a separate gpio controller for each of the child nodes. So >> just create a real struct device (like we do for every other >> "compatible" DT node) and probe each of them properly using the device >> driver core. > > Then I believe the modifications are non-trivial. Maybe Linus and Rob > can comment which way is better, fix the dts or modify the gpio-dwapb.c. > Personally, I prefer fixing dts, because this doesn't remove or modify > any used properties or compatible string, it just removes the unused > compatible string.
You appear to be assuming that:
A) There a no consumers of DTBs and DT bindings other than Linux. B) No Linux user ever updates their kernel image without also updating their DTB.
I can assure you that, in general, neither of those hold true. Hacking DTs to work around internal implementation details in Linux is rarely if ever a good or even viable idea.
Robin.
> > Thanks > > >> >>> +} >>> + >>> +static struct platform_driver dwapb_gpio_port_driver = { >>> + .driver = { >>> + .name = "gpio-dwapb-port", >>> + .of_match_table = dwapb_port_of_match, >>> + }, >>> + .probe = dwapb_gpio_port_probe, >>> +}; >>> +module_platform_driver(dwapb_gpio_port_driver); >>> + >>> MODULE_LICENSE("GPL"); >>> MODULE_AUTHOR("Jamie Iles"); >>> MODULE_DESCRIPTION("Synopsys DesignWare APB GPIO driver"); >>> > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >
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