#9391 NORM 1.5-F11: HPET address in ACPI table is not valid (was: Can't turn on HPET)

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#9391: HPET address in ACPI table is not valid
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           Reporter:  cjb                  |       Owner:  wmb at firmworks.com
               Type:  defect               |      Status:  new              
           Priority:  normal               |   Milestone:  1.5-F11          
          Component:  ofw - open firmware  |     Version:  not specified    
         Resolution:                       |    Keywords:                   
        Next_action:  never set            |    Verified:  0                
Deployment_affected:                       |   Blockedby:                   
           Blocking:                       |  
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Changes (by dsaxena):

 * cc: dsaxena (added)
  * owner:  dsaxena => wmb at firmworks.com
  * component:  kernel => ofw - open firmware


Comment:

 Basically what is happening is that the value we are getting from ACPI for
 hpet_address (see arch/x86/kernel/acpi/boot.c)is 0xffffffff and when we
 try to ioremap() that, we run into the following code in the low-level
 remap path:

 {{{
 static void __iomem *__ioremap_caller(resource_size_t phys_addr,
                 unsigned long size, unsigned long prot_val, void *caller)
 {
 ...
         /* Don't allow wraparound or zero size */
         last_addr = phys_addr + size - 1;
         if (!size || last_addr < phys_addr)
                 return NULL;
 }}}

 The HPET driver in the kernel does not check for the return value, and
 when we try to access the HPET via the NULL mapping, we get page fault and
 die miserably. This is obviously a bug and I'll submit a patch upstream to
 gracefully exit the HPET init path in this situation; however, for us to
 have the HPET working, we need to get the proper info from ACPI.

-- 
Ticket URL: <http://dev.laptop.org/ticket/9391#comment:1>
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