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Subject: PAGE_GUARDED
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
 linuxppc-dev@lists.ozlabs.org, darren@stevens-zone.net
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From: Christian Zigotzky <chzigotzky@xenosoft.de>
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Date: Tue, 24 May 2016 12:48:48 +0200
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Ben,

Thanks for the hint. I'm sorry I don't know how pgprot_noncached() works.

I tried:

1) range.size, pgprot_noncached()

2) range.size, pgprot_val(pgprot_noncached(__pgprot(0))));

3) range.size, pgprot_val(pgprot_noncached_wc(__pgprot(0))));

Unfortunately without any success.

I'd like to modify the following code for the ATi SB600 southbridge chipset:

/* Workaround for lack of device tree */
                        if (primary) {
                                __ioremap_at(range.cpu_addr, (void 
*)ISA_IO_BASE,
                                range.size, _PAGE_NO_CACHE|_PAGE_GUARDED);
                                hose->io_base_virt = (void *)_IO_BASE;
                                printk("Initialised io_base_virt 0x%lx 
_IO_BASE 0x%llx\n", (unsigned long)hose->io_base_virt, (unsigned long 
long)_IO_BASE);
                     }

This workaround works with the kernel 4.6 final. After the commit 
powerpc-4.7-1, the computer doesn't boot anymore.

Last message in the CFE firmware:

Booting Linux via __start()...

Cheers,

Christian


On 23 May 2016 at 10:01 AM, Benjamin Herrenschmidt wrote:
> On Mon, 2016-05-23 at 06:38 +0200, Christian Zigotzky wrote:
>> Hi All,
>>
>> You removed PAGE_GUARDED in the commit
>>
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commi
>> t/?id=c04a5880299eab3da8c10547db96ea9cdffd44a6
>>
>> We use
>>
>> range.size, _PAGE_NO_CACHE|_PAGE_GUARDED);
>>
>> This doesn't work anymore. What can we use instead?
> You should just use pgprot_noncached()
>
> Cheers,
> Ben.
>
>