[ARM_LINUX] ioremap() allowing to map system memory...

[sandeep kumar]

>please give your detail calling example, it is weired that you did not get
>0x0 returned.

I have the following code like below. In my case it is not returning NULL.
         /*
 * Don't allow RAM to be mapped - this causes problems with ARMv6+
 */
if (pfn_valid(pfn)) {
 printk(KERN_WARNING "BUG: Your driver calls ioremap() on system memory.
 This leads\n"
       KERN_WARNING "to architecturally unpredictable behaviour on ARMv6+,
and ioremap()\n"
       KERN_WARNING "will fail in the next kernel release.  Please fix your
driver.\n");
WARN_ON(1);
 }

Thanks
Sandeep


On Mon, Mar 4, 2013 at 1:32 PM, buyitian <buyit at live.cn> wrote:

> ________________________________
> > From: coolsandyforyou at gmail.com
> > Date: Sat, 2 Mar 2013 22:48:34 +0530
> > Subject: Re: [ARM_LINUX] ioremap() allowing to map system memory...
> > To: gprabhunath at gmail.com
> > CC: kernelnewbies at kernelnewbies.org
> >
> > >I passed a physical address 0x63ACD000. As expected it returned
> > 0x00000000. I am running linux version 3.5.1.
> > Mine is ARM, i donno about x86. In my case ioremap is successfule and
> > giving an address in ioremap() range of virtual memory map as
> > in http://www.arm.linux.org.uk/developer/memory.txt.
>
> please give your detail calling example, it is weired that you did not get
> 0x0 returned.
>
> maybe your platform overwirte the arch_ioremap_caller? please double check
> this.
> the default implementation for arch_ioremap_caller is as below:
> void __iomem * (*arch_ioremap_caller)(unsigned long, size_t,
>           unsigned int, void *) = __arm_ioremap_caller;
>
> in \arch\arm\mm\ioremap.c, in function __arm_ioremap_pfn_caller:
>
> /*
>  * Don't allow RAM to be mapped - this causes problems with ARMv6+
>  */
>  if (WARN_ON(pfn_valid(pfn)))
>    return NULL;
>
> you should get NULL if you are asking convert a valid memory.
>
> >
> >
> > On Sat, Mar 2, 2013 at 4:52 PM, Prabhu nath
> > <gprabhunath at gmail.com<mailto:gprabhunath at gmail.com>> wrote:
> > In principle, ioremap() will return 0x00000000 if the physical address
> > passed is of memory.
> > I just want you to double check the address you have passed to ioremap().
> > In my experiment on x86 Desktop machine with 2GB RAM. I passed a
> > physical address 0x63ACD000. As expected it returned 0x00000000. I am
> > running linux version 3.5.1.
> >
> >
> > Regards,
> > Prabhunath G
> > Linux Trainer
> > Bangalore
> >
> >
> > On Fri, Mar 1, 2013 at 5:57 PM, sandeep kumar
> > <coolsandyforyou at gmail.com<mailto:coolsandyforyou at gmail.com>> wrote:
> > >Looks like you are trying to pass the address of physical memory to
> > this function as a parameter and it is screwing up.
> > Yes, i intentionally gave some physical address which is part of system
> > memory.
> > My problem infact is, it is not screwing up. It is allowing me to do
> > that. Its not 'panic'ing
> >
> >
> > On Fri, Mar 1, 2013 at 4:58 PM, Prabhu nath
> > <gprabhunath at gmail.com<mailto:gprabhunath at gmail.com>> wrote:
> >
> >
> > On Fri, Mar 1, 2013 at 4:48 PM, sandeep kumar
> > <coolsandyforyou at gmail.com<mailto:coolsandyforyou at gmail.com>> wrote:
> > Hi All
> > I am using ARM based board.
> > In mine,
> > i did the following...
> >
> > void __iomem *tcpm_base = ioremap_nocache(0x03B00000, 10*SZ_3MB);
> >
> > Actually i didnt reserve the 30MB memory @ 0x3B00000. But still the
> > call is succesful and i am able to read the memory.
> >
> > In the logs it is just showing a warning, to fix my driver as i am
> > calling ioremap() on system memory.
> >
> > However if i try to write something on that memory, then only it is
> > calling panic()..
> >
> > Don't you think it should throw panic()while calling the ioremap()
> > itself. Because this sounds like a serious violation...
> >
> > What say?
> >
> > To my knowledge, ioremap is used only to map the device related
> > physical address to kernel virtual address. i.e. this function will
> > only map either device registers or device memory to kernel virtual
> > address.
> >
> > Looks like you are trying to pass the address of physical memory to
> > this function as a parameter and it is screwing up.
> >
> > Please verify.
> >
> > Regards,
> > Prabhu
> >
> > --
> > With regards,
> > Sandeep Kumar Anantapalli,
> >
> > _______________________________________________
> > Kernelnewbies mailing list
> > Kernelnewbies at kernelnewbies.org<mailto:Kernelnewbies at kernelnewbies.org>
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> >
> >
> >
> >
> >
> > --
> > With regards,
> > Sandeep Kumar Anantapalli,
> >
> >
> >
> >
> > --
> > With regards,
> > Sandeep Kumar Anantapalli,
> >
> > _______________________________________________ Kernelnewbies mailing
> > list Kernelnewbies at kernelnewbies.org
> > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>



-- 
With regards,
Sandeep Kumar Anantapalli,
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