swiotlb: Make SWIOTLB_NO_FORCE perform no allocation

When SWIOTLB_NO_FORCE is used, there should really be no allocations of
default_nslabs to occur since we are not going to use those slabs. If a
platform was somehow setting swiotlb_no_force and a later call to
swiotlb_init() was to be made we would still be proceeding with
allocating the default SWIOTLB size (64MB), whereas if swiotlb=noforce
was set on the kernel command line we would have only allocated 2KB.

This would be inconsistent and the point of initializing default_nslabs
to 1, was intended to allocate the minimum amount of memory possible, so
simply remove that minimal allocation period.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 539c76b..0a5b6f7 100644 (file)
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -83,12 +83,10 @@ setup_io_tlb_npages(char *str)
        }
        if (*str == ',')
                ++str;
-       if (!strcmp(str, "force")) {
+       if (!strcmp(str, "force"))
                swiotlb_force = SWIOTLB_FORCE;
-       } else if (!strcmp(str, "noforce")) {
+       else if (!strcmp(str, "noforce"))
                swiotlb_force = SWIOTLB_NO_FORCE;
-               default_nslabs = 1;
-       }
 
        return 0;
 }
@@ -174,6 +172,9 @@ int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int verbose)
        struct io_tlb_mem *mem;
        size_t alloc_size;
 
+       if (swiotlb_force == SWIOTLB_NO_FORCE)
+               return 0;
+
        /* protect against double initialization */
        if (WARN_ON_ONCE(io_tlb_default_mem))
                return -ENOMEM;
@@ -211,6 +212,9 @@ swiotlb_init(int verbose)
        size_t bytes = PAGE_ALIGN(default_nslabs << IO_TLB_SHIFT);
        void *tlb;
 
+       if (swiotlb_force == SWIOTLB_NO_FORCE)
+               return;
+
        /* Get IO TLB memory from the low pages */
        tlb = memblock_alloc_low(bytes, PAGE_SIZE);
        if (!tlb)
@@ -240,6 +244,9 @@ swiotlb_late_init_with_default_size(size_t default_size)
        unsigned int order;
        int rc = 0;
 
+       if (swiotlb_force == SWIOTLB_NO_FORCE)
+               return 0;
+
        /*
         * Get IO TLB memory from the low pages
         */
@@ -276,6 +283,9 @@ swiotlb_late_init_with_tbl(char *tlb, unsigned long nslabs)
        unsigned long bytes = nslabs << IO_TLB_SHIFT, i;
        struct io_tlb_mem *mem;
 
+       if (swiotlb_force == SWIOTLB_NO_FORCE)
+               return 0;
+
        /* protect against double initialization */
        if (WARN_ON_ONCE(io_tlb_default_mem))
                return -ENOMEM;