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From 3092242447d1132bf1e0d13efbc133c50224b1a7 Mon Sep 17 00:00:00 2001
From: detule <ogjoneski@gmail.com>
Date: Tue, 2 Oct 2018 04:10:08 -0400
Subject: [PATCH] staging: vchiq_arm: Usa a DMA pool for small bulks
During a bulk transfer we request a DMA allocation to hold the
scatter-gather list. Most of the time, this allocation is small
(<< PAGE_SIZE), however it can be requested at a high enough frequency
to cause fragmentation and/or stress the CMA allocator (think time
spent in compaction here, or during allocations elsewhere).
Implement a pool to serve up small DMA allocations, falling back
to a coherent allocation if the request is greater than
VCHIQ_DMA_POOL_SIZE.
Signed-off-by: Oliver Gjoneski <ogjoneski@gmail.com>
---
.../interface/vchiq_arm/vchiq_arm.c | 36 ++++++++++++++++---
1 file changed, 32 insertions(+), 4 deletions(-)
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
@@ -22,6 +22,7 @@
#include <linux/platform_device.h>
#include <linux/compat.h>
#include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
#include <linux/rcupdate.h>
#include <linux/delay.h>
#include <linux/slab.h>
@@ -51,6 +52,8 @@
#define ARM_DS_ACTIVE BIT(2)
+#define VCHIQ_DMA_POOL_SIZE PAGE_SIZE
+
/* Override the default prefix, which would be vchiq_arm (from the filename) */
#undef MODULE_PARAM_PREFIX
#define MODULE_PARAM_PREFIX DEVICE_NAME "."
@@ -93,6 +96,7 @@ struct vchiq_pagelist_info {
struct pagelist *pagelist;
size_t pagelist_buffer_size;
dma_addr_t dma_addr;
+ bool is_from_pool;
enum dma_data_direction dma_dir;
unsigned int num_pages;
unsigned int pages_need_release;
@@ -113,6 +117,7 @@ static void __iomem *g_regs;
* of 32.
*/
static unsigned int g_cache_line_size = 32;
+static struct dma_pool *g_dma_pool;
static unsigned int g_use_36bit_addrs = 0;
static unsigned int g_fragments_size;
static char *g_fragments_base;
@@ -156,8 +161,14 @@ cleanup_pagelistinfo(struct vchiq_pageli
if (pagelistinfo->pages_need_release)
unpin_user_pages(pagelistinfo->pages, pagelistinfo->num_pages);
- dma_free_coherent(g_dev, pagelistinfo->pagelist_buffer_size,
- pagelistinfo->pagelist, pagelistinfo->dma_addr);
+ if (pagelistinfo->is_from_pool) {
+ dma_pool_free(g_dma_pool, pagelistinfo->pagelist,
+ pagelistinfo->dma_addr);
+ } else {
+ dma_free_coherent(g_dev, pagelistinfo->pagelist_buffer_size,
+ pagelistinfo->pagelist,
+ pagelistinfo->dma_addr);
+ }
}
/* There is a potential problem with partial cache lines (pages?)
@@ -178,6 +189,7 @@ create_pagelist(char *buf, char __user *
u32 *addrs;
unsigned int num_pages, offset, i, k;
int actual_pages;
+ bool is_from_pool;
size_t pagelist_size;
struct scatterlist *scatterlist, *sg;
int dma_buffers;
@@ -207,8 +219,16 @@ create_pagelist(char *buf, char __user *
/* Allocate enough storage to hold the page pointers and the page
* list
*/
- pagelist = dma_alloc_coherent(g_dev, pagelist_size, &dma_addr,
- GFP_KERNEL);
+ if (pagelist_size > VCHIQ_DMA_POOL_SIZE) {
+ pagelist = dma_alloc_coherent(g_dev,
+ pagelist_size,
+ &dma_addr,
+ GFP_KERNEL);
+ is_from_pool = false;
+ } else {
+ pagelist = dma_pool_alloc(g_dma_pool, GFP_KERNEL, &dma_addr);
+ is_from_pool = true;
+ }
vchiq_log_trace(vchiq_arm_log_level, "%s - %pK", __func__, pagelist);
@@ -229,6 +249,7 @@ create_pagelist(char *buf, char __user *
pagelistinfo->pagelist = pagelist;
pagelistinfo->pagelist_buffer_size = pagelist_size;
pagelistinfo->dma_addr = dma_addr;
+ pagelistinfo->is_from_pool = is_from_pool;
pagelistinfo->dma_dir = (type == PAGELIST_WRITE) ?
DMA_TO_DEVICE : DMA_FROM_DEVICE;
pagelistinfo->num_pages = num_pages;
@@ -569,6 +590,13 @@ int vchiq_platform_init(struct platform_
g_dev = dev;
g_dma_dev = dma_dev ?: dev;
+ g_dma_pool = dmam_pool_create("vchiq_scatter_pool", dev,
+ VCHIQ_DMA_POOL_SIZE, g_cache_line_size,
+ 0);
+ if (!g_dma_pool) {
+ dev_err(dev, "failed to create dma pool");
+ return -ENOMEM;
+ }
vchiq_log_info(vchiq_arm_log_level,
"vchiq_init - done (slots %pK, phys %pad)",
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