linux-kernel - Re: [PATCH] ARM: allow, but warn, when issuing ioremap() on RAM

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Date:	Sun, 10 Oct 2010 04:52:36 +0300
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Greg KH <greg@...ah.com>,
	linux-main <linux-kernel@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Arnd Hannemann <arnd@...dnet.de>,
	Han Jonghun <jonghun79.han@...il.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Hemant Pedanekar <hemantp@...com>
Subject: Re: [PATCH] ARM: allow, but warn, when issuing ioremap() on RAM

On Sat, Oct 9, 2010 at 12:21 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> static unsigned long reserve_mem(struct meminfo *mi, unsigned long size)
> {
>        unsigned long addr = ~0;
>        int i;
>
>        for (i = mi->nr_banks - 1; i >= 0; i--)
>                if (mi->bank[i].size >= size) {
>                        mi->bank[i].size -= size;
>                        addr = mi->bank[i].start + mi->bank[i].size;
>                        break;
>                }
>
>        return addr;
> }
>
> static void __init my_fixup(struct machine_desc *desc, struct tag *tags,
>                            char **cmdline, struct meminfo *mi)
> {
>        omapfb_buffer_phys = reserve_mem(mi, 32*1048576);
>        if (omapfb_buffer_phys == ~0)
>                pr_warn("Unable to allocate omapfb buffer\n");
> }
>
> Then later:
>
>        omapfb_buffer = ioremap(omapfb_buffer_phys, 32*1048576);
>
> That's a damned simple and direct implementation of exactly what I
> described, and results in something which is much more architecturally
> correct than what's going on today.

I tried this, it doesn't work.

At the time 'fixup' is called, 'meminfo' is empty; the tags haven't
been parsed. So my solution is to move the memblock_add() after
'reserve', and pass 'meminfo' as an argument:

--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -272,8 +272,6 @@ void __init arm_memblock_init(struct meminfo *mi,
struct machine_desc *mdesc)
        int i;

        memblock_init();
-       for (i = 0; i < mi->nr_banks; i++)
-               memblock_add(mi->bank[i].start, mi->bank[i].size);

        /* Register the kernel text, kernel data and initrd with memblock. */
 #ifdef CONFIG_XIP_KERNEL
@@ -295,7 +293,10 @@ void __init arm_memblock_init(struct meminfo *mi,
struct machine_desc *mdesc)

        /* reserve any platform specific memblock areas */
        if (mdesc->reserve)
-               mdesc->reserve();
+               mdesc->reserve(mi);
+
+       for (i = 0; i < mi->nr_banks; i++)
+               memblock_add(mi->bank[i].start, mi->bank[i].size);

        memblock_analyze();
        memblock_dump_all();

-- 
Felipe Contreras
--
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