Hi John, On 27.01.2016 02:37, John Stultz wrote: > This patchset extends on Andy Yan's reboot mode driver > work from here: https://lkml.org/lkml/2016/1/12/315 > > It adds reboot mode/reason support for devices that use > an SRAM location to communicate with the bootloader. > > Doing this via an SRAM subnode was a suggestion from > Arnd, but I worry this implementation isn't yet ideal, > since I spent quite a bit of time futzing with getting > the sram dts entry to work properly. So I suspect there > will be a number of suggestions for improvements. sorry, I missed that discussion, what are the problems you've encountered? Probably SRAM driver is ready to serve your purposes? I believe I'm screwing up some HiSilicon specifics, but here is a rough draft, which you may find helpful: 1. Add SRAM node with defined reboot-reason area: ---8<--- diff --git a/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts b/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts index 8185251..c35f5ed 100644 --- a/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts +++ b/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts @@ -31,6 +31,20 @@ device_type = "memory"; reg = <0x0 0x0 0x0 0x40000000>; }; + + sram@5f01000 { + compatible = "mmio-sram"; + reg = <0x0 0x05f01000 0x0 0x00001000>; + ranges = <0x0 0x0 0x05f01000 0x00001000>; + + #address-cells = <1>; + #size-cells = <1>; + + reboot-reason: reboot-reason { + reg = <0x0 0x4>; + pool; + }; + }; }; &uart2 { ---8<--- 2. Reference reboot-reason node from reboot mode driver's node, probably you need to add an optional property (here "reason-storage") to its binding: ---8<--- reboot-mode { compatible = "syscon-reboot-mode"; [snip] reason-storage = <&reboot-reason>; } ---8<--- 3. In reboot-mode driver read or write to that SRAM partition: ---8<--- storage = of_gen_pool_get(reboot_mode_np, "reason-storage", 0); if (!storage) goto no_storage; size = gen_pool_size(storage); base = gen_pool_alloc(storage, pool_size); if (!base) return -EINVAL; writel(0x77665501, base); gen_pool_free(storage, base, size); no_storage: return 0; ---8<--- There is one noticeable benefit of this approach - you don't need to write another driver and you don't need to add another DT binding. With best wishes, Vladimir > Again, this series dependson Andy's patch set above, > but also was developed & tested against the 4.1 based > hikey tree, so at least the hikey dts patch won't apply. > I'm mostly sending this out for just a rough initial > review of the dts and conceptual usage of sram subnodes. > > Also, it was pointed out that the hikey dts entry for > this really should be added by the UEFI firmware, since > alternative bootloaders may be used which do not support > this feature. So the hikey dts patch isn't likely to ever > go upstream, but its a useful illustration for how other > devices might use this driver. > > Cc: Andy Yan <andy.yan@xxxxxxxxxxxxxx> > Cc: Rob Herring <robh@xxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Thierry Reding <treding@xxxxxxxxxx> > Cc: Heiko Stübner <heiko@xxxxxxxxx> > Cc: Caesar Wang <wxt@xxxxxxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Guodong Xu <guodong.xu@xxxxxxxxxx> > Cc: Haojian Zhuang <haojian.zhuang@xxxxxxxxxx> > Cc: Vishal Bhoj <vishal.bhoj@xxxxxxxxxx> > Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> > Cc: devicetree@xxxxxxxxxxxxxxx > Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx> > > John Stultz (3): > dt-bindings: power: reset: Add document for sram-reboot-mode driver > power: reset: Add sram-reboot-mode driver > dts: hikey: Add hikey support for sram-reboot-mode > > .../bindings/power/reset/sram-reboot-mode.txt | 47 +++++++++++++++ > arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts | 36 ++++++++++++ > arch/arm64/configs/hikey_defconfig | 3 + > drivers/power/reset/Kconfig | 9 +++ > drivers/power/reset/Makefile | 1 + > drivers/power/reset/sram-reboot-mode.c | 66 ++++++++++++++++++++++ > 6 files changed, 162 insertions(+) > create mode 100644 Documentation/devicetree/bindings/power/reset/sram-reboot-mode.txt > create mode 100644 drivers/power/reset/sram-reboot-mode.c > -- 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
