Re: Reading from ISP registers fails

[Roger Quadros <ext-roger.quadros@nokia.com>]

ext matthias schwarz wrote:
> Hello there,
> 
> i just wrote a little kernel-module, which only executes the following
> lines of code:
> 
> u32 syn_mode;
> void* iomem;
> struct resource* resource_ptr;
> 
> resource_ptr = request_mem_region(0x480BC000, 0xFFF, "isp_ccdc");
> 
> iomem = ioremap(OMAP3ISP_REG(ISP_SYSCONFIG), 8);
> if(iomem == NULL) {
> 	printk("ioremap returned zero\n");
> 	return 0;
> }
> syn_mode = ioread32(iomem);
> 
> 
> 
> The resulting behaviour does not depend on which ISP register i am
> trying to read, it also happens for "OMAP3ISP_CCDC_REG_BASE +
> ISPCCDC_SYN_MODE" for example. And also when using
> "omap_readl(address)" to read those registers.
> 
> So when this code is executed i get:
> 
> Unhandled fault: external abort on non-linefetch (0x1028) at 0xd80bc004
> Internal error: : 1028 [#1] PREEMPT
> Internal error: : 1028 [#1] PREEMPT
> Modules linked in:Modules linked in: camera(+) camera(+) ipv6 ipv6
> 
> CPU: 0    Not tainted  (2.6.28-omap1 #15)
> [...]
> 
> 
> Hope someone can help me with what might be wrong.
> Thank you,
> Matthias
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You need to enable interface clocks before accessing any peripheral registers.

regards,
-roger