IB/qib: Use cache inhibitted and guarded mapping on powerpc

The driver was requesting for a writethrough mapping. But with those
flags we will end up with an SAO mapping because we now have memory
conherence always enabled. ie, the existing mapping will end up with a
WIMG value 0b1110 which is Strong Access Order.

Update this to use cache inhibitted guarded mapping.

Cc: Doug Ledford <dledford@redhat.com>
Cc: Sean Hefty <sean.hefty@intel.com>
Cc: Hal Rosenstock <hal.rosenstock@gmail.com>
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

drivers/infiniband/hw/qib/qib_file_ops.c

@@ -822,10 +822,7 @@ static int mmap_piobufs(struct vm_area_struct *vma,
 	phys = dd->physaddr + piobufs;
 
 #if defined(__powerpc__)
-	/* There isn't a generic way to specify writethrough mappings */
-	pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE;
-	pgprot_val(vma->vm_page_prot) |= _PAGE_WRITETHRU;
-	pgprot_val(vma->vm_page_prot) &= ~_PAGE_GUARDED;
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 #endif
 
 	/*

drivers/infiniband/hw/qib/qib_pcie.c

@@ -144,13 +144,7 @@ int qib_pcie_ddinit(struct qib_devdata *dd, struct pci_dev *pdev,
 	addr = pci_resource_start(pdev, 0);
 	len = pci_resource_len(pdev, 0);
 
-#if defined(__powerpc__)
-	/* There isn't a generic way to specify writethrough mappings */
-	dd->kregbase = __ioremap(addr, len, _PAGE_NO_CACHE | _PAGE_WRITETHRU);
-#else
 	dd->kregbase = ioremap_nocache(addr, len);
-#endif
-
 	if (!dd->kregbase)
 		return -ENOMEM;