diff options
Diffstat (limited to 'Documentation/x86')
| -rw-r--r-- | Documentation/x86/pat.txt | 24 | ||||
| -rw-r--r-- | Documentation/x86/x86_64/boot-options.txt | 11 |
2 files changed, 24 insertions, 11 deletions
diff --git a/Documentation/x86/pat.txt b/Documentation/x86/pat.txt index c93ff5f4c0dd..cf08c9fff3cd 100644 --- a/Documentation/x86/pat.txt +++ b/Documentation/x86/pat.txt @@ -80,6 +80,30 @@ pci proc | -- | -- | WC | | | | | ------------------------------------------------------------------- +Advanced APIs for drivers +------------------------- +A. Exporting pages to users with remap_pfn_range, io_remap_pfn_range, +vm_insert_pfn + +Drivers wanting to export some pages to userspace do it by using mmap +interface and a combination of +1) pgprot_noncached() +2) io_remap_pfn_range() or remap_pfn_range() or vm_insert_pfn() + +With PAT support, a new API pgprot_writecombine is being added. So, drivers can +continue to use the above sequence, with either pgprot_noncached() or +pgprot_writecombine() in step 1, followed by step 2. + +In addition, step 2 internally tracks the region as UC or WC in memtype +list in order to ensure no conflicting mapping. + +Note that this set of APIs only works with IO (non RAM) regions. If driver +wants to export a RAM region, it has to do set_memory_uc() or set_memory_wc() +as step 0 above and also track the usage of those pages and use set_memory_wb() +before the page is freed to free pool. + + + Notes: -- in the above table mean "Not suggested usage for the API". Some of the --'s diff --git a/Documentation/x86/x86_64/boot-options.txt b/Documentation/x86/x86_64/boot-options.txt index f6d561a1a9b2..34c13040a718 100644 --- a/Documentation/x86/x86_64/boot-options.txt +++ b/Documentation/x86/x86_64/boot-options.txt @@ -79,17 +79,6 @@ Timing Report when timer interrupts are lost because some code turned off interrupts for too long. - nmi_watchdog=NUMBER[,panic] - NUMBER can be: - 0 don't use an NMI watchdog - 1 use the IO-APIC timer for the NMI watchdog - 2 use the local APIC for the NMI watchdog using a performance counter. Note - This will use one performance counter and the local APIC's performance - vector. - When panic is specified panic when an NMI watchdog timeout occurs. - This is useful when you use a panic=... timeout and need the box - quickly up again. - nohpet Don't use the HPET timer. |