target/linux/bcm27xx/patches-5.4/950-0121-vchiq_2835_arm-Implement-a-DMA-pool-for-small-bulk-t.patch

   1 From c2acd59177043f78446357f560e5436b0318ceb6 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] vchiq_2835_arm: Implement a DMA pool for small bulk
   5  transfers (#2699)
   6
   7 During a bulk transfer we request a DMA allocation to hold the
   8 scatter-gather list.  Most of the time, this allocation is small
   9 (<< PAGE_SIZE), however it can be requested at a high enough frequency
  10 to cause fragmentation and/or stress the CMA allocator (think time
  11 spent in compaction here, or during allocations elsewhere).
  12
  13 Implement a pool to serve up small DMA allocations, falling back
  14 to a coherent allocation if the request is greater than
  15 VCHIQ_DMA_POOL_SIZE.
  16
  17 Signed-off-by: Oliver Gjoneski <ogjoneski@gmail.com>
  18 ---
  19  .../interface/vchiq_arm/vchiq_2835_arm.c      | 38 ++++++++++++++++---
  20  1 file changed, 33 insertions(+), 5 deletions(-)
  21
  22 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
  23 +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
  24 @@ -7,6 +7,7 @@
  25  #include <linux/interrupt.h>
  26  #include <linux/pagemap.h>
  27  #include <linux/dma-mapping.h>
  28 +#include <linux/dmapool.h>
  29  #include <linux/io.h>
  30  #include <linux/platform_device.h>
  31  #include <linux/uaccess.h>
  32 @@ -28,6 +29,8 @@
  33  #define BELL0  0x00
  34  #define BELL2  0x08
  35
  36 +#define VCHIQ_DMA_POOL_SIZE PAGE_SIZE
  37 +
  38  struct vchiq_2835_state {
  39         int inited;
  40         struct vchiq_arm_state arm_state;
  41 @@ -37,6 +40,7 @@ struct vchiq_pagelist_info {
  42         struct pagelist *pagelist;
  43         size_t pagelist_buffer_size;
  44         dma_addr_t dma_addr;
  45 +       bool is_from_pool;
  46         enum dma_data_direction dma_dir;
  47         unsigned int num_pages;
  48         unsigned int pages_need_release;
  49 @@ -57,6 +61,7 @@ static void __iomem *g_regs;
  50   * of 32.
  51   */
  52  static unsigned int g_cache_line_size = 32;
  53 +static struct dma_pool *g_dma_pool;
  54  static unsigned int g_fragments_size;
  55  static char *g_fragments_base;
  56  static char *g_free_fragments;
  57 @@ -161,6 +166,14 @@ int vchiq_platform_init(struct platform_
  58         }
  59
  60         g_dev = dev;
  61 +       g_dma_pool = dmam_pool_create("vchiq_scatter_pool", dev,
  62 +                                     VCHIQ_DMA_POOL_SIZE, g_cache_line_size,
  63 +                                     0);
  64 +       if (!g_dma_pool) {
  65 +               dev_err(dev, "failed to create dma pool");
  66 +               return -ENOMEM;
  67 +       }
  68 +
  69         vchiq_log_info(vchiq_arm_log_level,
  70                 "vchiq_init - done (slots %pK, phys %pad)",
  71                 vchiq_slot_zero, &slot_phys);
  72 @@ -339,9 +352,14 @@ cleanup_pagelistinfo(struct vchiq_pageli
  73                 for (i = 0; i < pagelistinfo->num_pages; i++)
  74                         put_page(pagelistinfo->pages[i]);
  75         }
  76 -
  77 -       dma_free_coherent(g_dev, pagelistinfo->pagelist_buffer_size,
  78 -                         pagelistinfo->pagelist, pagelistinfo->dma_addr);
  79 +       if (pagelistinfo->is_from_pool) {
  80 +               dma_pool_free(g_dma_pool, pagelistinfo->pagelist,
  81 +                             pagelistinfo->dma_addr);
  82 +       } else {
  83 +               dma_free_coherent(g_dev, pagelistinfo->pagelist_buffer_size,
  84 +                                 pagelistinfo->pagelist,
  85 +                                 pagelistinfo->dma_addr);
  86 +       }
  87  }
  88
  89  /* There is a potential problem with partial cache lines (pages?)
  90 @@ -361,6 +379,7 @@ create_pagelist(char __user *buf, size_t
  91         u32 *addrs;
  92         unsigned int num_pages, offset, i, k;
  93         int actual_pages;
  94 +       bool is_from_pool;
  95         size_t pagelist_size;
  96         struct scatterlist *scatterlist, *sg;
  97         int dma_buffers;
  98 @@ -387,8 +406,16 @@ create_pagelist(char __user *buf, size_t
  99         /* Allocate enough storage to hold the page pointers and the page
 100          * list
 101          */
 102 -       pagelist = dma_alloc_coherent(g_dev, pagelist_size, &dma_addr,
 103 -                                     GFP_KERNEL);
 104 +       if (pagelist_size > VCHIQ_DMA_POOL_SIZE) {
 105 +               pagelist = dma_alloc_coherent(g_dev,
 106 +                                              pagelist_size,
 107 +                                              &dma_addr,
 108 +                                              GFP_KERNEL);
 109 +               is_from_pool = false;
 110 +       } else {
 111 +               pagelist = dma_pool_alloc(g_dma_pool, GFP_KERNEL, &dma_addr);
 112 +               is_from_pool = true;
 113 +       }
 114
 115         vchiq_log_trace(vchiq_arm_log_level, "%s - %pK", __func__, pagelist);
 116
 117 @@ -409,6 +436,7 @@ create_pagelist(char __user *buf, size_t
 118         pagelistinfo->pagelist = pagelist;
 119         pagelistinfo->pagelist_buffer_size = pagelist_size;
 120         pagelistinfo->dma_addr = dma_addr;
 121 +       pagelistinfo->is_from_pool = is_from_pool;
 122         pagelistinfo->dma_dir =  (type == PAGELIST_WRITE) ?
 123                                   DMA_TO_DEVICE : DMA_FROM_DEVICE;
 124         pagelistinfo->num_pages = num_pages;