ALSA: memalloc: Unify x86 SG-buffer handling (take#3)

This is a second attempt to unify the x86-specific SG-buffer handling
code with the new standard non-contiguous page handler.

The first try (in commit 2d9ea39917a4) failed due to the wrong page
and address calculations, hence reverted. (And the second try failed
due to a copy&paste error.) Now it's corrected with the previous fix
for noncontig pages, and the proper sg page iteration by this patch.

After the migration, SNDRV_DMA_TYPE_DMA_SG becomes identical with
SNDRV_DMA_TYPE_NONCONTIG on x86, while others still fall back to
SNDRV_DMA_TYPE_DEV.

Tested-by: Alex Xu (Hello71) <[e-mail]>
Tested-by: Harald Arnesen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Takashi Iwai <[e-mail]>

include/sound/memalloc.h

···
 #define SNDRV_DMA_TYPE_CONTINUOUS	1	/* continuous no-DMA memory */
 #define SNDRV_DMA_TYPE_DEV		2	/* generic device continuous */
 #define SNDRV_DMA_TYPE_DEV_WC		5	/* continuous write-combined */
-#ifdef CONFIG_SND_DMA_SGBUF
-#define SNDRV_DMA_TYPE_DEV_SG		3	/* generic device SG-buffer */
-#define SNDRV_DMA_TYPE_DEV_WC_SG	6	/* SG write-combined */
-#else
-#define SNDRV_DMA_TYPE_DEV_SG	SNDRV_DMA_TYPE_DEV /* no SG-buf support */
-#define SNDRV_DMA_TYPE_DEV_WC_SG	SNDRV_DMA_TYPE_DEV_WC
-#endif
 #ifdef CONFIG_GENERIC_ALLOCATOR
 #define SNDRV_DMA_TYPE_DEV_IRAM		4	/* generic device iram-buffer */
 #else
···
 #define SNDRV_DMA_TYPE_VMALLOC		7	/* vmalloc'ed buffer */
 #define SNDRV_DMA_TYPE_NONCONTIG	8	/* non-coherent SG buffer */
 #define SNDRV_DMA_TYPE_NONCOHERENT	9	/* non-coherent buffer */
+#ifdef CONFIG_SND_DMA_SGBUF
+#define SNDRV_DMA_TYPE_DEV_SG		SNDRV_DMA_TYPE_NONCONTIG
+#define SNDRV_DMA_TYPE_DEV_WC_SG	6	/* SG write-combined */
+#else
+#define SNDRV_DMA_TYPE_DEV_SG	SNDRV_DMA_TYPE_DEV /* no SG-buf support */
+#define SNDRV_DMA_TYPE_DEV_WC_SG	SNDRV_DMA_TYPE_DEV_WC
+#endif
 
 /*
  * info for buffer allocation

sound/core/Makefile

···
 snd-pcm-y := pcm.o pcm_native.o pcm_lib.o pcm_misc.o \
 		pcm_memory.o memalloc.o
 snd-pcm-$(CONFIG_SND_PCM_TIMER) += pcm_timer.o
-snd-pcm-$(CONFIG_SND_DMA_SGBUF) += sgbuf.o
 snd-pcm-$(CONFIG_SND_PCM_ELD) += pcm_drm_eld.o
 snd-pcm-$(CONFIG_SND_PCM_IEC958) += pcm_iec958.o
 

sound/core/memalloc.c

···
 	.get_chunk_size = snd_dma_noncontig_get_chunk_size,
 };
 
+/* x86-specific SG-buffer with WC pages */
+#ifdef CONFIG_SND_DMA_SGBUF
+#define sg_wc_address(it) ((unsigned long)page_address(sg_page_iter_page(it)))
+
+static void *snd_dma_sg_wc_alloc(struct snd_dma_buffer *dmab, size_t size)
+{
+	void *p = snd_dma_noncontig_alloc(dmab, size);
+	struct sg_table *sgt = dmab->private_data;
+	struct sg_page_iter iter;
+
+	if (!p)
+		return NULL;
+	for_each_sgtable_page(sgt, &iter, 0)
+		set_memory_wc(sg_wc_address(&iter), 1);
+	return p;
+}
+
+static void snd_dma_sg_wc_free(struct snd_dma_buffer *dmab)
+{
+	struct sg_table *sgt = dmab->private_data;
+	struct sg_page_iter iter;
+
+	for_each_sgtable_page(sgt, &iter, 0)
+		set_memory_wb(sg_wc_address(&iter), 1);
+	snd_dma_noncontig_free(dmab);
+}
+
+static int snd_dma_sg_wc_mmap(struct snd_dma_buffer *dmab,
+			      struct vm_area_struct *area)
+{
+	area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
+	return dma_mmap_noncontiguous(dmab->dev.dev, area,
+				      dmab->bytes, dmab->private_data);
+}
+
+static const struct snd_malloc_ops snd_dma_sg_wc_ops = {
+	.alloc = snd_dma_sg_wc_alloc,
+	.free = snd_dma_sg_wc_free,
+	.mmap = snd_dma_sg_wc_mmap,
+	.sync = snd_dma_noncontig_sync,
+	.get_addr = snd_dma_noncontig_get_addr,
+	.get_page = snd_dma_noncontig_get_page,
+	.get_chunk_size = snd_dma_noncontig_get_chunk_size,
+};
+#endif /* CONFIG_SND_DMA_SGBUF */
+
 /*
  * Non-coherent pages allocator
  */
···
 	[SNDRV_DMA_TYPE_DEV_WC] = &snd_dma_wc_ops,
 	[SNDRV_DMA_TYPE_NONCONTIG] = &snd_dma_noncontig_ops,
 	[SNDRV_DMA_TYPE_NONCOHERENT] = &snd_dma_noncoherent_ops,
+#ifdef CONFIG_SND_DMA_SGBUF
+	[SNDRV_DMA_TYPE_DEV_WC_SG] = &snd_dma_sg_wc_ops,
+#endif
 #ifdef CONFIG_GENERIC_ALLOCATOR
 	[SNDRV_DMA_TYPE_DEV_IRAM] = &snd_dma_iram_ops,
 #endif /* CONFIG_GENERIC_ALLOCATOR */
 #endif /* CONFIG_HAS_DMA */
-#ifdef CONFIG_SND_DMA_SGBUF
-	[SNDRV_DMA_TYPE_DEV_SG] = &snd_dma_sg_ops,
-	[SNDRV_DMA_TYPE_DEV_WC_SG] = &snd_dma_sg_ops,
-#endif
 };
 
 static const struct snd_malloc_ops *snd_dma_get_ops(struct snd_dma_buffer *dmab)

sound/core/sgbuf.c

···
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * Scatter-Gather buffer
- *
- *  Copyright (c) by Takashi Iwai <[e-mail]>
- */
-
-#include <linux/slab.h>
-#include <linux/mm.h>
-#include <linux/vmalloc.h>
-#include <linux/export.h>
-#include <sound/memalloc.h>
-#include "memalloc_local.h"
-
-struct snd_sg_page {
-	void *buf;
-	dma_addr_t addr;
-};
-
-struct snd_sg_buf {
-	int size;	/* allocated byte size */
-	int pages;	/* allocated pages */
-	int tblsize;	/* allocated table size */
-	struct snd_sg_page *table;	/* address table */
-	struct page **page_table;	/* page table (for vmap/vunmap) */
-	struct device *dev;
-};
-
-/* table entries are align to 32 */
-#define SGBUF_TBL_ALIGN		32
-#define sgbuf_align_table(tbl)	ALIGN((tbl), SGBUF_TBL_ALIGN)
-
-static void snd_dma_sg_free(struct snd_dma_buffer *dmab)
-{
-	struct snd_sg_buf *sgbuf = dmab->private_data;
-	struct snd_dma_buffer tmpb;
-	int i;
-
-	if (!sgbuf)
-		return;
-
-	vunmap(dmab->area);
-	dmab->area = NULL;
-
-	tmpb.dev.type = SNDRV_DMA_TYPE_DEV;
-	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
-		tmpb.dev.type = SNDRV_DMA_TYPE_DEV_WC;
-	tmpb.dev.dev = sgbuf->dev;
-	for (i = 0; i < sgbuf->pages; i++) {
-		if (!(sgbuf->table[i].addr & ~PAGE_MASK))
-			continue; /* continuous pages */
-		tmpb.area = sgbuf->table[i].buf;
-		tmpb.addr = sgbuf->table[i].addr & PAGE_MASK;
-		tmpb.bytes = (sgbuf->table[i].addr & ~PAGE_MASK) << PAGE_SHIFT;
-		snd_dma_free_pages(&tmpb);
-	}
-
-	kfree(sgbuf->table);
-	kfree(sgbuf->page_table);
-	kfree(sgbuf);
-	dmab->private_data = NULL;
-}
-
-#define MAX_ALLOC_PAGES		32
-
-static void *snd_dma_sg_alloc(struct snd_dma_buffer *dmab, size_t size)
-{
-	struct snd_sg_buf *sgbuf;
-	unsigned int i, pages, chunk, maxpages;
-	struct snd_dma_buffer tmpb;
-	struct snd_sg_page *table;
-	struct page **pgtable;
-	int type = SNDRV_DMA_TYPE_DEV;
-	pgprot_t prot = PAGE_KERNEL;
-	void *area;
-
-	dmab->private_data = sgbuf = kzalloc(sizeof(*sgbuf), GFP_KERNEL);
-	if (!sgbuf)
-		return NULL;
-	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG) {
-		type = SNDRV_DMA_TYPE_DEV_WC;
-#ifdef pgprot_noncached
-		prot = pgprot_noncached(PAGE_KERNEL);
-#endif
-	}
-	sgbuf->dev = dmab->dev.dev;
-	pages = snd_sgbuf_aligned_pages(size);
-	sgbuf->tblsize = sgbuf_align_table(pages);
-	table = kcalloc(sgbuf->tblsize, sizeof(*table), GFP_KERNEL);
-	if (!table)
-		goto _failed;
-	sgbuf->table = table;
-	pgtable = kcalloc(sgbuf->tblsize, sizeof(*pgtable), GFP_KERNEL);
-	if (!pgtable)
-		goto _failed;
-	sgbuf->page_table = pgtable;
-
-	/* allocate pages */
-	maxpages = MAX_ALLOC_PAGES;
-	while (pages > 0) {
-		chunk = pages;
-		/* don't be too eager to take a huge chunk */
-		if (chunk > maxpages)
-			chunk = maxpages;
-		chunk <<= PAGE_SHIFT;
-		if (snd_dma_alloc_pages_fallback(type, dmab->dev.dev,
-						 chunk, &tmpb) < 0) {
-			if (!sgbuf->pages)
-				goto _failed;
-			size = sgbuf->pages * PAGE_SIZE;
-			break;
-		}
-		chunk = tmpb.bytes >> PAGE_SHIFT;
-		for (i = 0; i < chunk; i++) {
-			table->buf = tmpb.area;
-			table->addr = tmpb.addr;
-			if (!i)
-				table->addr |= chunk; /* mark head */
-			table++;
-			*pgtable++ = virt_to_page(tmpb.area);
-			tmpb.area += PAGE_SIZE;
-			tmpb.addr += PAGE_SIZE;
-		}
-		sgbuf->pages += chunk;
-		pages -= chunk;
-		if (chunk < maxpages)
-			maxpages = chunk;
-	}
-
-	sgbuf->size = size;
-	area = vmap(sgbuf->page_table, sgbuf->pages, VM_MAP, prot);
-	if (!area)
-		goto _failed;
-	return area;
-
- _failed:
-	snd_dma_sg_free(dmab); /* free the table */
-	return NULL;
-}
-
-static dma_addr_t snd_dma_sg_get_addr(struct snd_dma_buffer *dmab,
-				      size_t offset)
-{
-	struct snd_sg_buf *sgbuf = dmab->private_data;
-	dma_addr_t addr;
-
-	addr = sgbuf->table[offset >> PAGE_SHIFT].addr;
-	addr &= ~((dma_addr_t)PAGE_SIZE - 1);
-	return addr + offset % PAGE_SIZE;
-}
-
-static struct page *snd_dma_sg_get_page(struct snd_dma_buffer *dmab,
-					size_t offset)
-{
-	struct snd_sg_buf *sgbuf = dmab->private_data;
-	unsigned int idx = offset >> PAGE_SHIFT;
-
-	if (idx >= (unsigned int)sgbuf->pages)
-		return NULL;
-	return sgbuf->page_table[idx];
-}
-
-static unsigned int snd_dma_sg_get_chunk_size(struct snd_dma_buffer *dmab,
-					      unsigned int ofs,
-					      unsigned int size)
-{
-	struct snd_sg_buf *sg = dmab->private_data;
-	unsigned int start, end, pg;
-
-	start = ofs >> PAGE_SHIFT;
-	end = (ofs + size - 1) >> PAGE_SHIFT;
-	/* check page continuity */
-	pg = sg->table[start].addr >> PAGE_SHIFT;
-	for (;;) {
-		start++;
-		if (start > end)
-			break;
-		pg++;
-		if ((sg->table[start].addr >> PAGE_SHIFT) != pg)
-			return (start << PAGE_SHIFT) - ofs;
-	}
-	/* ok, all on continuous pages */
-	return size;
-}
-
-static int snd_dma_sg_mmap(struct snd_dma_buffer *dmab,
-			   struct vm_area_struct *area)
-{
-	if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG)
-		area->vm_page_prot = pgprot_writecombine(area->vm_page_prot);
-	return -ENOENT; /* continue with the default mmap handler */
-}
-
-const struct snd_malloc_ops snd_dma_sg_ops = {
-	.alloc = snd_dma_sg_alloc,
-	.free = snd_dma_sg_free,
-	.get_addr = snd_dma_sg_get_addr,
-	.get_page = snd_dma_sg_get_page,
-	.get_chunk_size = snd_dma_sg_get_chunk_size,
-	.mmap = snd_dma_sg_mmap,
-};