diff options
| author | Todd Poynor <toddpoynor@google.com> | 2018-08-09 20:21:05 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-08-27 19:43:44 +0200 |
| commit | 7b49682bdc6cf6f7d55e7c7e74415c2b101a9671 (patch) | |
| tree | 1929d45bb06b94c0ecceb558f20002141c2c040d /drivers/staging/gasket | |
| parent | 717264bab46e774e196574c77aae5f103b9b2f26 (diff) | |
| download | linux-7b49682bdc6cf6f7d55e7c7e74415c2b101a9671.tar.bz2 | |
staging: gasket: page table: remove extraneous memory barriers
Some explicit memory barriers in the page table code are not necessary,
either because:
(a) The barrier follows a non-relaxed MMIO access that already performs
a read or write memory barrier.
(b) The barrier follows DMA API calls for which the device-visible
effects of IOMMU programming are guaranteed to be flushed to the IOMMU
prior to the call returning, and doesn't need to sync with normal memory
access.
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/staging/gasket')
| -rw-r--r-- | drivers/staging/gasket/gasket_page_table.c | 15 |
1 files changed, 5 insertions, 10 deletions
diff --git a/drivers/staging/gasket/gasket_page_table.c b/drivers/staging/gasket/gasket_page_table.c index 4d2499269499..53492f4fad6a 100644 --- a/drivers/staging/gasket/gasket_page_table.c +++ b/drivers/staging/gasket/gasket_page_table.c @@ -317,8 +317,6 @@ static void gasket_free_extended_subtable(struct gasket_page_table *pg_tbl, /* Release the page table from the device */ writeq(0, slot); - /* Force sync around the address release. */ - mb(); if (pte->dma_addr) dma_unmap_page(pg_tbl->device, pte->dma_addr, PAGE_SIZE, @@ -504,8 +502,6 @@ static int gasket_perform_mapping(struct gasket_page_table *pg_tbl, (void *)page_to_phys(page)); return -1; } - /* Wait until the page is mapped. */ - mb(); } /* Make the DMA-space address available to the device. */ @@ -604,12 +600,13 @@ static void gasket_perform_unmapping(struct gasket_page_table *pg_tbl, */ for (i = 0; i < num_pages; i++) { /* release the address from the device, */ - if (is_simple_mapping || ptes[i].status == PTE_INUSE) + if (is_simple_mapping || ptes[i].status == PTE_INUSE) { writeq(0, &slots[i]); - else + } else { ((u64 __force *)slots)[i] = 0; - /* Force sync around the address release. */ - mb(); + /* sync above PTE update before updating mappings */ + wmb(); + } /* release the address from the driver, */ if (ptes[i].status == PTE_INUSE) { @@ -898,8 +895,6 @@ static int gasket_alloc_extended_subtable(struct gasket_page_table *pg_tbl, /* Map the page into DMA space. */ pte->dma_addr = dma_map_page(pg_tbl->device, pte->page, 0, PAGE_SIZE, DMA_BIDIRECTIONAL); - /* Wait until the page is mapped. */ - mb(); /* make the addresses available to the device */ dma_addr = (pte->dma_addr + pte->offset) | GASKET_VALID_SLOT_FLAG; |