target/linux/bcm27xx/patches-6.1/950-0330-staging-vchiq_arm-Usa-a-DMA-pool-for-small-bulks.patch

   1 From dfbd92cb3b27855e388e17dc5035fa0e5fb70474 Mon Sep 17 00:00:00 2001
   2 From: detule <ogjoneski@gmail.com>
   3 Date: Tue, 2 Oct 2018 04:10:08 -0400
   4 Subject: [PATCH] staging: vchiq_arm: Usa a DMA pool for small bulks
   5
   6 During a bulk transfer we request a DMA allocation to hold the
   7 scatter-gather list.  Most of the time, this allocation is small
   8 (<< PAGE_SIZE), however it can be requested at a high enough frequency
   9 to cause fragmentation and/or stress the CMA allocator (think time
  10 spent in compaction here, or during allocations elsewhere).
  11
  12 Implement a pool to serve up small DMA allocations, falling back
  13 to a coherent allocation if the request is greater than
  14 VCHIQ_DMA_POOL_SIZE.
  15
  16 Signed-off-by: Oliver Gjoneski <ogjoneski@gmail.com>
  17 ---
  18  .../interface/vchiq_arm/vchiq_arm.c           | 33 ++++++++++++++++---
  19  1 file changed, 29 insertions(+), 4 deletions(-)
  20
  21 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
  22 +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
  23 @@ -22,6 +22,7 @@
  24  #include <linux/platform_device.h>
  25  #include <linux/compat.h>
  26  #include <linux/dma-mapping.h>
  27 +#include <linux/dmapool.h>
  28  #include <linux/rcupdate.h>
  29  #include <linux/delay.h>
  30  #include <linux/slab.h>
  31 @@ -51,6 +52,8 @@
  32
  33  #define ARM_DS_ACTIVE  BIT(2)
  34
  35 +#define VCHIQ_DMA_POOL_SIZE PAGE_SIZE
  36 +
  37  /* Override the default prefix, which would be vchiq_arm (from the filename) */
  38  #undef MODULE_PARAM_PREFIX
  39  #define MODULE_PARAM_PREFIX DEVICE_NAME "."
  40 @@ -133,6 +136,7 @@ struct vchiq_pagelist_info {
  41         struct pagelist *pagelist;
  42         size_t pagelist_buffer_size;
  43         dma_addr_t dma_addr;
  44 +       bool is_from_pool;
  45         enum dma_data_direction dma_dir;
  46         unsigned int num_pages;
  47         unsigned int pages_need_release;
  48 @@ -153,6 +157,7 @@ static void __iomem *g_regs;
  49   * of 32.
  50   */
  51  static unsigned int g_cache_line_size = 32;
  52 +static struct dma_pool *g_dma_pool;
  53  static unsigned int g_use_36bit_addrs = 0;
  54  static unsigned int g_fragments_size;
  55  static char *g_fragments_base;
  56 @@ -195,8 +200,13 @@ cleanup_pagelistinfo(struct vchiq_instan
  57         if (pagelistinfo->pages_need_release)
  58                 unpin_user_pages(pagelistinfo->pages, pagelistinfo->num_pages);
  59
  60 -       dma_free_coherent(instance->state->dev, pagelistinfo->pagelist_buffer_size,
  61 -                         pagelistinfo->pagelist, pagelistinfo->dma_addr);
  62 +       if (pagelistinfo->is_from_pool) {
  63 +               dma_pool_free(g_dma_pool, pagelistinfo->pagelist,
  64 +                             pagelistinfo->dma_addr);
  65 +       } else {
  66 +               dma_free_coherent(instance->state->dev, pagelistinfo->pagelist_buffer_size,
  67 +                                 pagelistinfo->pagelist, pagelistinfo->dma_addr);
  68 +       }
  69  }
  70
  71  static inline bool
  72 @@ -231,6 +241,7 @@ create_pagelist(struct vchiq_instance *i
  73         u32 *addrs;
  74         unsigned int num_pages, offset, i, k;
  75         int actual_pages;
  76 +       bool is_from_pool;
  77         size_t pagelist_size;
  78         struct scatterlist *scatterlist, *sg;
  79         int dma_buffers;
  80 @@ -260,8 +271,14 @@ create_pagelist(struct vchiq_instance *i
  81         /* Allocate enough storage to hold the page pointers and the page
  82          * list
  83          */
  84 -       pagelist = dma_alloc_coherent(instance->state->dev, pagelist_size, &dma_addr,
  85 -                                     GFP_KERNEL);
  86 +       if (pagelist_size > VCHIQ_DMA_POOL_SIZE) {
  87 +               pagelist = dma_alloc_coherent(instance->state->dev, pagelist_size, &dma_addr,
  88 +                                             GFP_KERNEL);
  89 +               is_from_pool = false;
  90 +       } else {
  91 +               pagelist = dma_pool_alloc(g_dma_pool, GFP_KERNEL, &dma_addr);
  92 +               is_from_pool = true;
  93 +       }
  94
  95         vchiq_log_trace(vchiq_arm_log_level, "%s - %pK", __func__, pagelist);
  96
  97 @@ -282,6 +299,7 @@ create_pagelist(struct vchiq_instance *i
  98         pagelistinfo->pagelist = pagelist;
  99         pagelistinfo->pagelist_buffer_size = pagelist_size;
 100         pagelistinfo->dma_addr = dma_addr;
 101 +       pagelistinfo->is_from_pool = is_from_pool;
 102         pagelistinfo->dma_dir =  (type == PAGELIST_WRITE) ?
 103                                   DMA_TO_DEVICE : DMA_FROM_DEVICE;
 104         pagelistinfo->num_pages = num_pages;
 105 @@ -616,6 +634,13 @@ static int vchiq_platform_init(struct pl
 106         }
 107
 108         g_dma_dev = dma_dev ?: dev;
 109 +       g_dma_pool = dmam_pool_create("vchiq_scatter_pool", dev,
 110 +                                     VCHIQ_DMA_POOL_SIZE, g_cache_line_size,
 111 +                                     0);
 112 +       if (!g_dma_pool) {
 113 +               dev_err(dev, "failed to create dma pool");
 114 +               return -ENOMEM;
 115 +       }
 116
 117         vchiq_log_info(vchiq_arm_log_level, "vchiq_init - done (slots %pK, phys %pad)",
 118                        vchiq_slot_zero, &slot_phys);