From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladimir Zapolskiy Subject: Re: [RFC][PATCH 0/3] SRAM reboot mode driver Date: Wed, 27 Jan 2016 10:50:01 +0200 Message-ID: <56A884B9.5020201@mentor.com> References: <1453855080-17760-1-git-send-email-john.stultz@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <1453855080-17760-1-git-send-email-john.stultz@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: John Stultz , lkml Cc: Andy Yan , Rob Herring , Arnd Bergmann , Thierry Reding , =?UTF-8?Q?Heiko_St=c3=bcbner?= , Caesar Wang , Kees Cook , Guodong Xu , Haojian Zhuang , Vishal Bhoj , Bjorn Andersson , devicetree@vger.kernel.org, Android Kernel Team List-Id: devicetree@vger.kernel.org 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 >=20 > It adds reboot mode/reason support for devices that use > an SRAM location to communicate with the bootloader. >=20 > 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 =3D "memory"; reg =3D <0x0 0x0 0x0 0x40000000>; }; + + sram@5f01000 { + compatible =3D "mmio-sram"; + reg =3D <0x0 0x05f01000 0x0 0x00001000>; + ranges =3D <0x0 0x0 0x05f01000 0x00001000>; + + #address-cells =3D <1>; + #size-cells =3D <1>; + + reboot-reason: reboot-reason { + reg =3D <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") t= o its binding: ---8<--- reboot-mode { compatible =3D "syscon-reboot-mode"; [snip] reason-storage =3D <&reboot-reason>; } ---8<--- 3. In reboot-mode driver read or write to that SRAM partition: ---8<--- storage =3D of_gen_pool_get(reboot_mode_np, "reason-storage", 0); if (!storage) goto no_storage; size =3D gen_pool_size(storage); base =3D 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. >=20 > 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. >=20 > Cc: Andy Yan > Cc: Rob Herring > Cc: Arnd Bergmann > Cc: Thierry Reding > Cc: Heiko St=C3=BCbner > Cc: Caesar Wang > Cc: Kees Cook > Cc: Guodong Xu > Cc: Haojian Zhuang > Cc: Vishal Bhoj > Cc: Bjorn Andersson > Cc: devicetree@vger.kernel.org > Cc: Android Kernel Team >=20 > 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 >=20 > .../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/sra= m-reboot-mode.txt > create mode 100644 drivers/power/reset/sram-reboot-mode.c >=20