From 3092242447d1132bf1e0d13efbc133c50224b1a7 Mon Sep 17 00:00:00 2001 From: detule 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 --- .../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 #include #include +#include #include #include #include @@ -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)",