[PATCH 1/6] [SRU][K] ALSA: memalloc: Try dma_alloc_noncontiguous() at first

[Koba Ko]

From: Takashi Iwai <tiwai at suse.de>

BugLink: https://bugs.launchpad.net/bugs/2009136

The latest fix for the non-contiguous memalloc helper changed the
allocation method for a non-IOMMU system to use only the fallback
allocator.  This should have worked, but it caused a problem sometimes
when too many non-contiguous pages are allocated that can't be treated
by HD-audio controller.

As a quirk workaround, go back to the original strategy: use
dma_alloc_noncontiguous() at first, and apply the fallback only when
it fails, but only for non-IOMMU case.

We'll need a better fix in the fallback code as well, but this
workaround should paper over most cases.

Fixes: 9736a325137b ("ALSA: memalloc: Don't fall back for SG-buffer with IOMMU")
Reported-by: Linus Torvalds <torvalds at linux-foundation.org>
Link: https://lore.kernel.org/r/CAHk-=wgSH5ubdvt76gNwa004ooZAEJL_1Q-Fyw5M2FDdqL==dg@mail.gmail.com
Link: https://lore.kernel.org/r/20221112084718.3305-1-tiwai@suse.de
Change-Id: I9ec6c1e04aff4e876c66b033424f442f276e46ce
Signed-off-by: Takashi Iwai <tiwai at suse.de>
(cherry picked from commit 9d8e536d36e75e76614fe09ffab9a1df95b8b666)
Signed-off-by: Koba Ko <koba.ko at canonical.com>
---
 sound/core/memalloc.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/sound/core/memalloc.c b/sound/core/memalloc.c
index 5b2842c3d17e4..0ebb1e4b95352 100644
--- a/sound/core/memalloc.c
+++ b/sound/core/memalloc.c
@@ -519,8 +519,10 @@ static void *snd_dma_noncontig_alloc(struct snd_dma_buffer *dmab, size_t size)
 	struct sg_table *sgt;
 	void *p;
 
+	sgt = dma_alloc_noncontiguous(dmab->dev.dev, size, dmab->dev.dir,
+				      DEFAULT_GFP, 0);
 #ifdef CONFIG_SND_DMA_SGBUF
-	if (!get_dma_ops(dmab->dev.dev)) {
+	if (!sgt && !get_dma_ops(dmab->dev.dev)) {
 		if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
 			dmab->dev.type = SNDRV_DMA_TYPE_DEV_WC_SG_FALLBACK;
 		else
@@ -528,9 +530,6 @@ static void *snd_dma_noncontig_alloc(struct snd_dma_buffer *dmab, size_t size)
 		return snd_dma_sg_fallback_alloc(dmab, size);
 	}
 #endif
-
-	sgt = dma_alloc_noncontiguous(dmab->dev.dev, size, dmab->dev.dir,
-				      DEFAULT_GFP, 0);
 	if (!sgt)
 		return NULL;
 
-- 
2.25.1