Commit a5003fc04113 ("[ALSA] emu10k1 - simplify page allocation for synth")
switched from using the DMA allocator for synth DMA pages to manually
calling alloc_page().
However, this usage has an implicit assumption that the DMA address space
for the emu10k1-family chip is the same as the CPU physical address space
which is not true for a system with a IOMMU.

Since this made the synth part of the driver non-functional on such systems
let's effectively revert that commit (while keeping the
__synth_free_pages() simplification).

Signed-off-by: Maciej S. Szmigiero <m...@maciej.szmigiero.name>
---
Changes from v1: None in this patch.

Changes from v2: Keep the __synth_free_pages() simplification.

 sound/pci/emu10k1/memory.c | 44 +++++++++++++++++++++++++++-----------------
 1 file changed, 27 insertions(+), 17 deletions(-)

diff --git a/sound/pci/emu10k1/memory.c b/sound/pci/emu10k1/memory.c
index fcb04cbbc9ab..1d0ce7356bbd 100644
--- a/sound/pci/emu10k1/memory.c
+++ b/sound/pci/emu10k1/memory.c
@@ -461,10 +461,19 @@ static void get_single_page_range(struct snd_util_memhdr 
*hdr,
 static void __synth_free_pages(struct snd_emu10k1 *emu, int first_page,
                               int last_page)
 {
+       struct snd_dma_buffer dmab;
        int page;
 
+       dmab.dev.type = SNDRV_DMA_TYPE_DEV;
+       dmab.dev.dev = snd_dma_pci_data(emu->pci);
+
        for (page = first_page; page <= last_page; page++) {
-               free_page((unsigned long)emu->page_ptr_table[page]);
+               if (emu->page_ptr_table[page] == NULL)
+                       continue;
+               dmab.area = emu->page_ptr_table[page];
+               dmab.addr = emu->page_addr_table[page];
+               dmab.bytes = PAGE_SIZE;
+               snd_dma_free_pages(&dmab);
                emu->page_addr_table[page] = 0;
                emu->page_ptr_table[page] = NULL;
        }
@@ -476,30 +485,31 @@ static void __synth_free_pages(struct snd_emu10k1 *emu, 
int first_page,
 static int synth_alloc_pages(struct snd_emu10k1 *emu, struct 
snd_emu10k1_memblk *blk)
 {
        int page, first_page, last_page;
+       struct snd_dma_buffer dmab;
 
        emu10k1_memblk_init(blk);
        get_single_page_range(emu->memhdr, blk, &first_page, &last_page);
        /* allocate kernel pages */
        for (page = first_page; page <= last_page; page++) {
-               /* first try to allocate from <4GB zone */
-               struct page *p = alloc_page(GFP_KERNEL | GFP_DMA32 |
-                                           __GFP_NOWARN);
-               if (!p || (page_to_pfn(p) & ~(emu->dma_mask >> PAGE_SHIFT))) {
-                       if (p)
-                               __free_page(p);
-                       /* try to allocate from <16MB zone */
-                       p = alloc_page(GFP_ATOMIC | GFP_DMA |
-                                      __GFP_NORETRY | /* no OOM-killer */
-                                      __GFP_NOWARN);
-               }
-               if (!p) {
-                       __synth_free_pages(emu, first_page, page - 1);
-                       return -ENOMEM;
+               if (snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV,
+                                       snd_dma_pci_data(emu->pci),
+                                       PAGE_SIZE, &dmab) < 0)
+                       goto __fail;
+               if (!is_valid_page(emu, dmab.addr)) {
+                       snd_dma_free_pages(&dmab);
+                       goto __fail;
                }
-               emu->page_addr_table[page] = page_to_phys(p);
-               emu->page_ptr_table[page] = page_address(p);
+               emu->page_addr_table[page] = dmab.addr;
+               emu->page_ptr_table[page] = dmab.area;
        }
        return 0;
+
+__fail:
+       /* release allocated pages */
+       last_page = page - 1;
+       __synth_free_pages(emu, first_page, last_page);
+
+       return -ENOMEM;
 }
 
 /*

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