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Date: Tue, 8 Dec 2015 16:22:40 -0800
From: John Stultz <john.stultz@...aro.org>
To: Bjorn Andersson <bjorn.andersson@...ymobile.com>
Cc: lkml <linux-kernel@...r.kernel.org>,
Rob Herring <robh+dt@...nel.org>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Kumar Gala <galak@...eaurora.org>,
Vinay Simha BN <simhavcs@...il.com>,
Haojian Zhuang <haojian.zhuang@...aro.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
Android Kernel Team <kernel-team@...roid.com>,
agross@...eaurora.org,
"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [RFC][PATCH] misc: Introduce reboot_reason driver
On Tue, Dec 8, 2015 at 2:07 PM, Bjorn Andersson
<bjorn.andersson@...ymobile.com> wrote:
> On Tue 08 Dec 13:29 PST 2015, John Stultz wrote:
>
>> This patch adds a basic driver to allow for commands like
>> "reboot bootloader" and "reboot recovery" to communicate this
>> reboot-reason to the bootloader.
>>
>> This is commonly done on Android devices, in order to reboot
>> the device into fastboot or recovery mode. It also supports
>> custom OEM specific commands, via "reboot oem-<value>".
>>
>> This driver pulls the phys memory address from DT as well as
>> the magic reason values that are written to the address for
>> each mode.
>>
>> For an example, this patch also adds the DT support for
>> the nexus7 device via its dts (which is not yet upstream).
>>
>> Thoughts and feedback would be appreciated!
>>
>
> Good to see some work on this, I want it too :)
>
> I do however think this is Qualcomm specific in its implementation, so
> adding Andy and linux-arm-msm.
Right. So this is based off of the qualcomm implementation. But I'm
hoping to reuse it for other hardware.
> [..]
>> diff --git a/arch/arm/boot/dts/qcom-apq8064-nexus7-flo.dts b/arch/arm/boot/dts/qcom-apq8064-nexus7-flo.dts
>> index 5183d18..ee5dcb7 100644
>> --- a/arch/arm/boot/dts/qcom-apq8064-nexus7-flo.dts
>> +++ b/arch/arm/boot/dts/qcom-apq8064-nexus7-flo.dts
>> @@ -282,6 +282,15 @@
>> };
>> };
>>
>> + reboot_reason: reboot_reason@...3f65c {
>> + compatible = "reboot_reason";
>> + reg = <0x2A03F65C 0x4>;
>> + reason,none = <0x77665501>;
>> + reason,bootloader = <0x77665500>;
>> + reason,recovery = <0x77665502>;
>> + reason,oem = <0x6f656d00>;
>> + };
>> +
>
> This address refers to IMEM, which is shared with a number of other
> uses. So I think we should have a simple-mfd (and syscon) with this
> within.
Errr.. I'm going to have to read up there. I'm not super familiar with
any of those drivers, so I'll try to see how exactly they would map in
here.
> I like the fact that you don't hard code the magics in the
> implementation, as I've seen additions from multiple places - so perhaps
> it should be made even more flexible.
>
> OMAP seems to use strings here instead of magics, but the delivery
> mechanism looks to be the same. But I think of this as Qualcomm
> specific.
Yea. This is good feedback. EFI bootloaders have their own
implementations as well. I suspect we'll need a few different driver
"types" to handle these differences, ie: value vs string.
I'll maybe extend the compatible string to make it clear that this is
a "value" style, and we can extend it with a string type later if
folks care?
>> +static int reboot_reason(struct notifier_block *nb, unsigned long action,
>> + void *data)
>> +{
>> + char *cmd = (char *)data;
>> + long reason = reasons[NONE];
>> +
>> + if (!reboot_reason_addr)
>> + return NOTIFY_DONE;
>> +
>> + if (cmd != NULL) {
>> + if (!strncmp(cmd, "bootloader", 10))
>> + reason = reasons[BOOTLOADER];
>> + else if (!strncmp(cmd, "recovery", 8))
>> + reason = reasons[RECOVERY];
>> + else if (!strncmp(cmd, "oem-", 4)) {
>> + unsigned long code;
>> +
>> + if (!kstrtoul(cmd+4, 0, &code))
>> + reason = reasons[OEM] | (code & 0xff);
>> + }
>> + }
>
> In the case where we didn't find a match you should write the "normal"
> reason here, otherwise I think you will end up in recovery when recovery
> issues a reboot (in Android that is).
So, reason is initialized to NONE here. So that should handle this,
no? Or do you mean something more subtle?
>
>> +
>> + if (reason != -1)
>> + writel(reason, reboot_reason_addr);
>> + return NOTIFY_DONE;
>> +}
>> +
>> +static int reboot_reason_probe(struct platform_device *pdev)
>> +{
>> + struct resource *res;
>> + u32 val;
>> + int i;
>> +
>> + /* initialize the reasons */
>> + for (i = 0; i < MAX_REASONS; i++)
>> + reasons[i] = -1;
>> +
>> + /* Try to grab the reason io address */
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + reboot_reason_addr = devm_ioremap_resource(&pdev->dev, res);
>> + if (IS_ERR(reboot_reason_addr))
>> + return PTR_ERR(reboot_reason_addr);
>> +
>
> Please acquire this memory from a syscon (preferably the the parent
> simple-mfd).
Ok. Will look into this. Sorry for my unfamiliarity with these details.
>> + /* initialize specified reasons from DT */
>> + if (!of_property_read_u32(pdev->dev.of_node, "reason,none", &val))
>> + reasons[NONE] = val;
>> + if (!of_property_read_u32(pdev->dev.of_node, "reason,bootloader", &val))
>> + reasons[BOOTLOADER] = val;
>> + if (!of_property_read_u32(pdev->dev.of_node, "reason,recovery", &val))
>> + reasons[RECOVERY] = val;
>> + if (!of_property_read_u32(pdev->dev.of_node, "reason,oem", &val))
>> + reasons[OEM] = val;
>
> I would like for this to be less hard coded.
Any tips here on how to do so?
thanks for all the feedback!
-john
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