[PATCH] arm: socfpga: fix fetching cpu1start_addr for system with > 2GB of ram

[Dinh Nguyen]

On 10/01/2014 08:20 AM, Russell King - ARM Linux wrote:
> On Wed, Oct 01, 2014 at 06:02:14AM -0500, dinguyen at opensource.altera.com wrote:
>> From: Dinh Nguyen <dinguyen at opensource.altera.com>
>>
>> When CPU1 is brought out of reset, it's MMU is not turned yet, so it will only
>> be able to use physical addresses. For systems with 1GB or less, clearing
>> 0x40000000 will work just fine. However for systems with 2GB or more, we
>> need to clear at least 0x80000000.
>>
>> Essentially, the bic instruction is converting the cpu1start_addr from a
>> virtual to a physical address. We should be using bic 0xf0000000 for all
>> systems.
> 
> Err.  Why not do the job properly rather than create this type of hack?
> This is not a fast path, so it's really not required to code it for an
> absolute minimum number of cycles.  So...
> 
> 	adr	r0, 1f		@ physical address of '1'
> 	ldmia	r0, {r1, r2}	@ load virtual address of '1' and 'cpu1start_addr'
> 	sub	r0, r0, r1	@ offset between virtual and physical
> 	ldr	r2, [r2, r0]	@ load *cpu1start_addr
> 	bx	r2
> ...
> 	.align
> 1:	.long	.
> 	.long	cpu1start_addr
> 
> will fix it properly.
> 

Thanks for the suggestion and the code, but it didn't seem to work for
me. But I think I found a way to just load in the value of
cpu1start_addr directly with this patch. Please let me know what you
think of this solution:


diff --git a/arch/arm/mach-socfpga/headsmp.S
b/arch/arm/mach-socfpga/headsmp.S
index 95c115d..3ca9ed1 100644
--- a/arch/arm/mach-socfpga/headsmp.S
+++ b/arch/arm/mach-socfpga/headsmp.S
@@ -13,17 +13,14 @@
        .arch   armv7-a

 ENTRY(secondary_trampoline)
-       movw    r2, #:lower16:cpu1start_addr
-       movt  r2, #:upper16:cpu1start_addr
-
-       /* The socfpga VT cannot handle a 0xC0000000 page offset when
loading
-               the cpu1start_addr, we bit clear it. Tested on HW and VT. */
-       bic     r2, r2, #0x40000000
-
-       ldr     r0, [r2]
+       ldr     r0, 1f
        ldr     r1, [r0]
        bx      r1

+       .globl  cpu1start_addr
+cpu1start_addr:
+1:     .space  4
+
 ENTRY(secondary_trampoline_end)

 ENTRY(socfpga_secondary_startup)
diff --git a/arch/arm/mach-socfpga/socfpga.c
b/arch/arm/mach-socfpga/socfpga.c
index adbf383..0fe1883 100644
--- a/arch/arm/mach-socfpga/socfpga.c
+++ b/arch/arm/mach-socfpga/socfpga.c
@@ -29,7 +29,6 @@
 void __iomem *socfpga_scu_base_addr = ((void __iomem
*)(SOCFPGA_SCU_VIRT_BASE));
 void __iomem *sys_manager_base_addr;
 void __iomem *rst_manager_base_addr;
-unsigned long cpu1start_addr;