With current linus's tree, there is some difference between mmio > 1M and MMIO < 1M.
Actually it does not care about E820_RESERVED for > 1M range, because it doesn't have _BUSY.
For < 1M range,
a. MMIO is not with E820_RESERVED, the device driver will work.
b. MMIO is with E820_RESERVED, the device driver can not reserve it's mmio later. because that MMIO could have parent resource with "reserved" name and _BUSY flag
My patch -v3 will break a.
but my patch -v4 patch will make it work.
but looks -v4 is too tricky.
maybe we just need remove change like following.
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 7bca3c6..9849824 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -1094,7 +1094,7 @@ void __init e820_reserve_resources(void)
* pci device BAR resource and insert them later in
* pcibios_resource_survey()
*/
- if (e820.map[i].type != E820_RESERVED || res->start < (1ULL<<20)) {
+ if (e820.map[i].type != E820_RESERVED) {
res->flags |= IORESOURCE_BUSY;
insert_resource(&iomem_resource, res);
}
May need Linus to ack it.
Those strange devices could be some kind of virtual debug devices. and they like to use those low mmio range.
YH
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