linux-kernel - Re: [RFC PATCH] of: make MAX_RESERVED

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Date:   Sat, 24 Nov 2018 14:56:13 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Miles Chen <miles.chen@...iatek.com>
Cc:     Frank Rowand <frowand.list@...il.com>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-mediatek@...ts.infradead.org, wsd_upstream@...iatek.com
Subject: Re: [RFC PATCH] of: make MAX_RESERVED_REGIONS configurable

On Wed, Nov 21, 2018 at 8:51 PM Miles Chen <miles.chen@...iatek.com> wrote:
>
> On Wed, 2018-11-21 at 10:39 -0600, Rob Herring wrote:
> > On Wed, Nov 21, 2018 at 2:11 AM <miles.chen@...iatek.com> wrote:
> > >
> > > From: Miles Chen <miles.chen@...iatek.com>
> > >
> > > When we use more than 32 entries in /resered-memory,
> > > there will be an error message: "not enough space all defined regions.".
> > > We can increase MAX_RESERVED_REGIONS to fix this.
> > >
> > > commit 22f8cc6e3373 ("drivers: of: increase MAX_RESERVED_REGIONS to 32")
> > > increased MAX_RESERVED_REGIONS to 32 but I'm not sure if increasing
> > > MAX_RESERVED_REGIONS to 64 is suitable for everyone.
> > >
> > > In this RFC patch, CONFIG_MAX_OF_RESERVED_REGIONS is added and used as
> > > MAX_RESERVED_REGIONS. Add a sanity test to make sure that
> > > MAX_RESERVED_REGIONS is less than INIT_MEMBLOCK_REGIONS.
> > > Users can configure CONFIG_MAX_OF_RESERVED_REGIONS according to their
> > > need.
> >
> > I don't want a kconfig option for this. I think it should be dynamic instead.
> >
> > The current flow is like this:
> >
> > for each reserved node:
> >   - call memblock_reserve
> >   - Add info to reserved_mem array
> >
> > I think we should change it to:
> >
> > for each reserved node:
> >   - call memblock_reserve
> >   - count number of nodes
> >
> > Alloc array using memblock_alloc
> >
> > for each reserved node:
> >    - Add info to reserved_mem array
> >
>
> thanks for your comment.
>
> I reviewed the flow and it might be easier to count the
> nodes and setup array first:
>
> for each reserved node:
>     - count number of nodes
>
> Alloc array using memblock_alloc
>
>
> for each reserved node:
>    - call memblock_reserve

The order here is wrong. It is important that you reserve the memory
blocks before doing any allocations.

>    - Add info to reserved_mem array
>
> What do you think?
>
> > Rob
>
>