Message-ID: <20151105161315.GE32247@leverpostej>
Date:	Thu, 5 Nov 2015 16:13:15 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Leo Yan <leo.yan@...aro.org>
Cc:	Rob Herring <robherring2@...il.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Bintian Wang <bintian.wang@...wei.com>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	Wei Xu <xuwei5@...ilicon.com>,
	Yiping Xu <xuyiping@...ilicon.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>,
	Tyler Baker <tyler.baker@...aro.org>
Subject: Re: [PATCH 1/4] arm64: dts: Reserve memory regions for hi6220

On Thu, Nov 05, 2015 at 09:54:50PM +0800, Leo Yan wrote:
> On Thu, Oct 29, 2015 at 04:33:01PM +0800, Leo Yan wrote:
> > On Wed, Oct 28, 2015 at 11:32:29PM -0500, Rob Herring wrote:
> > > On Fri, Oct 9, 2015 at 9:20 AM, Leo Yan <leo.yan@...aro.org> wrote:
> > > > On Fri, Oct 09, 2015 at 08:50:13AM -0500, Rob Herring wrote:
> > > >> On Fri, Oct 9, 2015 at 8:30 AM, Mark Rutland <mark.rutland@....com> wrote:
> > > >> > On Fri, Oct 09, 2015 at 08:17:16AM -0500, Rob Herring wrote:
> > > >> >> On Thu, Oct 8, 2015 at 11:36 PM, Leo Yan <leo.yan@...aro.org> wrote:
> > > >> >> > On Hi6220, below memory regions in DDR have specific purpose:
> > > >> >> >
> > > >> >> >   0x05e0,0000 - 0x05ef,ffff: For MCU firmware using at runtime;
> > > >> >> >   0x06df,f000 - 0x06df,ffff: For mailbox message data;
> > > >> >> >   0x0740,f000 - 0x0740,ffff: For MCU firmware's section;
> > > >> >> >   0x3e00,0000 - 0x3fff,ffff: For OP-TEE.
> > > >> >> >
> > > >> >> > This patch reserves these memory regions in DT.
> > > >> >> >
> > > >> >> > Signed-off-by: Leo Yan <leo.yan@...aro.org>
> > > >> >> > ---
> > > >> >> >  arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts | 16 ++++++++++++----
> > > >> >> >  1 file changed, 12 insertions(+), 4 deletions(-)
> > > >> >> >
> > > >> >> > diff --git a/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts b/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts
> > > >> >> > index e36a539..e3f4cb3 100644
> > > >> >> > --- a/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts
> > > >> >> > +++ b/arch/arm64/boot/dts/hisilicon/hi6220-hikey.dts
> > > >> >> > @@ -7,9 +7,6 @@
> > > >> >> >
> > > >> >> >  /dts-v1/;
> > > >> >> >
> > > >> >> > -/*Reserved 1MB memory for MCU*/
> > > >> >> > -/memreserve/ 0x05e00000 0x00100000;
> > > >> >> > -
> > > >> >>
> > > >> >> Why does memreserve not work for you? You can have multiple entries.
> > > >> >>
> > > >> >> >  #include "hi6220.dtsi"
> > > >> >> >
> > > >> >> >  / {
> > > >> >> > @@ -24,8 +21,19 @@
> > > >> >> >                 stdout-path = "serial0:115200n8";
> > > >> >> >         };
> > > >> >> >
> > > >> >> > +       /*
> > > >> >> > +        * Reserve below regions from memory node:
> > > >> >> > +        *
> > > >> >> > +        *  - 0x05e0,0000 - 0x05ef,ffff: MCU firmware runtime using
> > > >> >> > +        *  - 0x06df,f000 - 0x06df,ffff: Mailbox message data
> > > >> >> > +        *  - 0x0740,f000 - 0x0740,ffff: MCU firmware section
> > > >> >> > +        *  - 0x3e00,0000 - 0x3fff,ffff: OP-TEE
> > > >> >> > +        */
> > > >> >> >         memory@0 {
> > > >> >> >                 device_type = "memory";
> > > >> >> > -               reg = <0x0 0x0 0x0 0x40000000>;
> > > >> >> > +               reg = <0x00000000 0x00000000 0x00000000 0x05e00000>,
> > > >> >> > +                     <0x00000000 0x05f00000 0x00000000 0x00eff000>,
> > > >> >> > +                     <0x00000000 0x06e00000 0x00000000 0x0060f000>,
> > > >> >> > +                     <0x00000000 0x07410000 0x00000000 0x36bf0000>;
> > > >> >>
> > > >> >> No, don't do this. Please use memreserve or reserved-memory binding[1]
> > > >> >> or combination of both. Probably reserved-memory if you need the
> > > >> >> kernel to access some of these regions.
> > > >> >
> > > >> > I disagree at least for those portions owned by the secure world. The
> > > >> > kernel shouldn't map those at all, so memreserve isn't appropriate. That
> > > >> > covers OP-TEE and the MCU firmware regions, and I'd expec the EFI memory
> > > >> > map to not list those as available to the kernel.
> > > >>
> > > >> I'm fine carving out the beginning or end, but otherwise think memory
> > > >> should correspond to the physical memory. We have a way to describe
> > > >> holes to keep out, so we should use them. If secure world uses the DT,
> > > >> then it would either want to know its region in memory or add the DT
> > > >> data to say what it is using. We need that to be easy to find or easy
> > > >> to set, respectively. The size secure world needs could vary as well.
> > > >>
> > > >> The fact that the kernel maps the memory is the kernel's problem, not
> > > >> a DT problem.
> > > >>
> > > >
> > > > Just give more input here. In previous time, we have long discussion [1];
> > > > So actually your suggestion is exactly same what my old patch.
> > > >
> > > > From previous discussion, i think here have an assumtion: Use UEFI as
> > > > bootloader, the kernel will ignore (or remove) memreserve and reserved-memory
> > > > nodes, so just like Mark said "the EFI memory map to not list those
> > > > as available to the kernel". My new patch is just to follow this and
> > > > also make sure they have same behavior for different bootloader
> > > > (between UEFI and uboot).
> > > 
> > > I've read thru the thread and see 2 main conclusions. Using
> > > reserved-memory is problematic since things like grub don't support
> > > that. That is fine and we should stick with /mem-reserve/ for now.
> > 
> > Thanks for reviewing, Rob.
> > 
> > One thing should note: after booting with UEFI, /memreserve/ nodes
> > will be deleted by UEFI stub; and _ONLY_ can use /reserved-memory/
> > node to reserve memory regions.
> > 
> > Ard have another patch [1], after applied this patch, then all
> > /memreserve/ nodes and /reserved-memory/ nodes nodes will be ignored
> > to scan after booting with UEFI stub.
> > 
> > This is make sense, that means UEFI need provide exactly correct memory
> > map info by self and totally not depend on DT structures.
> > 
> > Another minor difference between /memreserve/ node and /reserved-memory/
> > node is: we can add property "no-map" for /reserved-memory/; so that
> > means it will totally remove region from memory block. it's more safe
> > for the memory region will NOT be mapped twice with different mapping
> > attribution.
> > 
> > [1] http://archive.arm.linux.org.uk/lurker/message/20150922.002128.46757034.en.html
> > 
> > > The other thing is the desire to have the memory presented to the kernel
> > > be the same whether it comes from UEFI or DT structures. I can see why
> > > there is some desire to have that alignment, but that doesn't really
> > > buy us anything. We can't eliminate some code path in the kernel doing
> > > so. So I still think that the memory node should reflect all of memory
> > > as defined by the h/w and mem-reserve should be used for any software
> > > defined reserved regions.
> > 
> > i think before we engaged much thinking for UEFI, that's meaningful for
> > we found what's correct implementation for UEFI. We need make sure UEFI
> > will do correct thing for itself.
> > 
> > If only consider purly from DT's usage, i have no strong opinion to
> > stick to use memory node to carve memory regions out. It's okay for me to
> > go back to use /reserved-memory/ to reserved regions.
> > 
> > Mark, do you agree with this?
> 
> Ping ...
> 
> Hi Mark,
> 
> Could u help confirm for this? i'm planning to resend new version
> patch series in tommorrow, but it's better can get your feedback
> firstly.

Sorry for the delay.

I'm still of the opinion that given the kernel has no business even
reading this memory, it does not make sense to use a memreserve.

Given that, and the points about other software not knowing aobut
/reserved-memory/, I don't think it makes sense to describe the region
in the memory nodes.

Thanks,
Mark.
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