It is possible for a 32 bit x86 build to use a 64 bit DMA address.
There are two remaining spots where the IPA driver does a modulo
operation to check alignment of a DMA address, and under certain
conditions this can lead to a build error on i386 (at least).
The alignment checks we're doing are for power-of-2 values, and this
means the lower 32 bits of the DMA address can be used. This ensures
both operands to the modulo operator are 32 bits wide.
Reported-by: Randy Dunlap <rdun...@infradead.org>
Signed-off-by: Alex Elder <el...@linaro.org>
---
drivers/net/ipa/gsi.c | 11 +++++++----
drivers/net/ipa/ipa_table.c | 9 ++++++---
2 files changed, 13 insertions(+), 7 deletions(-)
diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
index 7f3e338ca7a72..b6355827bf900 100644
--- a/drivers/net/ipa/gsi.c
+++ b/drivers/net/ipa/gsi.c
@@ -1436,15 +1436,18 @@ static void gsi_evt_ring_rx_update(struct gsi_evt_ring
*evt_ring, u32 index)
/* Initialize a ring, including allocating DMA memory for its entries */
static int gsi_ring_alloc(struct gsi *gsi, struct gsi_ring *ring, u32 count)
{
- size_t size = count * GSI_RING_ELEMENT_SIZE;
+ u32 size = count * GSI_RING_ELEMENT_SIZE;
struct device *dev = gsi->dev;
dma_addr_t addr;
- /* Hardware requires a 2^n ring size, with alignment equal to size */
+ /* Hardware requires a 2^n ring size, with alignment equal to size.
+ * The size is a power of 2, so we can check alignment using just
+ * the bottom 32 bits for a DMA address of any size.
+ */
ring->virt = dma_alloc_coherent(dev, size, &addr, GFP_KERNEL);
- if (ring->virt && addr % size) {
+ if (ring->virt && lower_32_bits(addr) % size) {
dma_free_coherent(dev, size, ring->virt, addr);
- dev_err(dev, "unable to alloc 0x%zx-aligned ring buffer\n",
+ dev_err(dev, "unable to alloc 0x%x-aligned ring buffer\n",
size);
return -EINVAL; /* Not a good error value, but distinct */
} else if (!ring->virt) {
diff --git a/drivers/net/ipa/ipa_table.c b/drivers/net/ipa/ipa_table.c
index 988f2c2886b95..4236a50ff03ae 100644
--- a/drivers/net/ipa/ipa_table.c
+++ b/drivers/net/ipa/ipa_table.c
@@ -658,10 +658,13 @@ int ipa_table_init(struct ipa *ipa)
return -ENOMEM;
/* We put the "zero rule" at the base of our table area. The IPA
- * hardware requires rules to be aligned on a 128-byte boundary.
- * Make sure the allocation satisfies this constraint.
+ * hardware requires route and filter table rules to be aligned
+ * on a 128-byte boundary. As long as the alignment constraint
+ * is a power of 2, we can check alignment using just the bottom
+ * 32 bits for a DMA address of any size.
*/
- if (addr % IPA_TABLE_ALIGN) {
+ BUILD_BUG_ON(!is_power_of_2(IPA_TABLE_ALIGN));
+ if (lower_32_bits(addr) % IPA_TABLE_ALIGN) {
dev_err(dev, "table address %pad not %u-byte aligned\n",
&addr, IPA_TABLE_ALIGN);
dma_free_coherent(dev, size, virt, addr);
--
2.27.0
