OpenWrt – Rev 4
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From 88acd92a7cbcb8a6ae299b88554abbc9bedbae0a Mon Sep 17 00:00:00 2001
From: detule <ogjoneski@gmail.com>
Date: Tue, 2 Oct 2018 04:10:08 -0400
Subject: [PATCH 424/454] vchiq_2835_arm: Implement a DMA pool for small bulk
transfers (#2699)
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_2835_arm.c | 40 +++++++++++++++----
1 file changed, 33 insertions(+), 7 deletions(-)
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
@@ -37,6 +37,7 @@
#include <linux/interrupt.h>
#include <linux/pagemap.h>
#include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/uaccess.h>
@@ -59,6 +60,8 @@
#define BELL0 0x00
#define BELL2 0x08
+#define VCHIQ_DMA_POOL_SIZE PAGE_SIZE
+
typedef struct vchiq_2835_state_struct {
int inited;
VCHIQ_ARM_STATE_T arm_state;
@@ -68,6 +71,7 @@ struct vchiq_pagelist_info {
PAGELIST_T *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;
@@ -78,6 +82,7 @@ struct vchiq_pagelist_info {
static void __iomem *g_regs;
static unsigned int g_cache_line_size = sizeof(CACHE_LINE_SIZE);
+static struct dma_pool *g_dma_pool;
static unsigned int g_fragments_size;
static char *g_fragments_base;
static char *g_free_fragments;
@@ -193,6 +198,14 @@ int vchiq_platform_init(struct platform_
}
g_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)",
vchiq_slot_zero, &slot_phys);
@@ -377,9 +390,14 @@ cleanup_pagelistinfo(struct vchiq_pageli
for (i = 0; i < pagelistinfo->num_pages; i++)
put_page(pagelistinfo->pages[i]);
}
-
- 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?)
@@ -400,6 +418,7 @@ create_pagelist(char __user *buf, size_t
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;
@@ -417,10 +436,16 @@ create_pagelist(char __user *buf, size_t
/* Allocate enough storage to hold the page pointers and the page
** list
*/
- pagelist = dma_zalloc_coherent(g_dev,
- pagelist_size,
- &dma_addr,
- GFP_KERNEL);
+ if (pagelist_size > VCHIQ_DMA_POOL_SIZE) {
+ pagelist = dma_zalloc_coherent(g_dev,
+ pagelist_size,
+ &dma_addr,
+ GFP_KERNEL);
+ is_from_pool = false;
+ } else {
+ pagelist = dma_pool_zalloc(g_dma_pool, GFP_KERNEL, &dma_addr);
+ is_from_pool = true;
+ }
vchiq_log_trace(vchiq_arm_log_level, "create_pagelist - %pK",
pagelist);
@@ -441,6 +466,7 @@ create_pagelist(char __user *buf, size_t
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;