linux-kernel - Re: [PATCH 6/7] arm: mediatek: enable gpt6 on boot up to make arch timer working

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAL_JsqJLn=dKKEgWFtvg_PnLFa5PEKM1J-M+fVbdirBWD2ii2A@mail.gmail.com>
Date:	Tue, 12 Aug 2014 10:03:48 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Matthias Brugger <matthias.bgg@...il.com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Mike Turquette <mturquette@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Jason Cooper <jason@...edaemon.net>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Stephen Warren <swarren@...dia.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	stefan@...er.ch, Maxime Ripard <maxime.ripard@...e-electrons.com>,
	"Berg, Anders" <anders.berg@....com>,
	Heiko Stübner <heiko@...ech.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 6/7] arm: mediatek: enable gpt6 on boot up to make arch
 timer working

On Tue, Aug 12, 2014 at 4:02 AM, Matthias Brugger
<matthias.bgg@...il.com> wrote:
> 2014-08-11 9:15 GMT+02:00 Linus Walleij <linus.walleij@...aro.org>:
>> On Thu, Jul 31, 2014 at 6:42 PM, Matthias Brugger
>> <matthias.bgg@...il.com> wrote:
>>
>>> We enable GTP6 which ungates the arch timer clock. Apart we write the
>>> frequency with which the timer is running in the CNTFREQ register.
>>> In the future this should be done in the bootloader.
>>>
>>> Signed-off-by: Matthias Brugger <matthias.bgg@...il.com>
>> (...)
>>
>>> +       if (of_machine_is_compatible("mediatek,mt6589")) {
>>> +               /* set cntfreq register which is not done in bootloader */
>>> +               asm volatile("mcr p15, 0, %0, c14, c0, 0" : : "r" (13000000));
>>
>> I guess this is for something like the ARM arch timer in
>> drivers/clocksource/arm_arch_timer.c
>>
>> Instead of doing this, use the DT property "clock-frequency" on
>> the ARM arch timer node, as that overrides the CP15 setting.
>>
>>> +
>>> +               /* turn on GPT6 which ungates arch timer clocks */
>>> +               gpt_base = ioremap(GPT6_CON_MT65xx, 0x04);
>>> +       }
>>> +
>>> +       /* enabel clock and set to free-run */
>>> +       if (gpt_base)
>>> +               writel(0x31, gpt_base);
>>
>> Why is this not done properly in the GPT driver (I guess
>> in drivers/clocksource/mtk_timer.c) instead of remapping
>> it and fiddling around in the machine?
>
> I didn't put it in the GPT driver, because that would mean, that you
> need to have the mtk_timer to be able to use the ARM arch timer.
> From my understanding this are two independent blocks in the SoC.
> Apart from that, as stated in the commit message, this patch is a
> workaround until we have a bootloader which does this for us.
> Therefore I thought the init_time function would be the better place to do this.

I agree that the bootloader is the right place, and the fixup in the
machine code until that is in place is the right place for the fixup.

Rob
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/