target/linux/brcm2708/patches-4.4/0175-bcm2835-sdhost-Only-claim-one-DMA-channel.patch

   1 From 06c169985c0884ce67377c79d27383e23f41e2cd Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Mon, 7 Mar 2016 16:46:39 +0000
   4 Subject: [PATCH 175/180] bcm2835-sdhost: Only claim one DMA channel
   5
   6 With both MMC controllers enabled there are few DMA channels left. The
   7 bcm2835-sdhost driver only uses DMA in one direction at a time, so it
   8 doesn't need to claim two channels.
   9
  10 See: https://github.com/raspberrypi/linux/issues/1327
  11
  12 Signed-off-by: Phil Elwell <phil@raspberrypi.org>
  13 ---
  14  arch/arm/boot/dts/bcm2708_common.dtsi |  5 +--
  15  drivers/mmc/host/bcm2835-sdhost.c     | 70 ++++++++++++++++++++++++-----------
  16  2 files changed, 50 insertions(+), 25 deletions(-)
  17
  18 --- a/arch/arm/boot/dts/bcm2708_common.dtsi
  19 +++ b/arch/arm/boot/dts/bcm2708_common.dtsi
  20 @@ -136,9 +136,8 @@
  21                         reg = <0x7e202000 0x100>;
  22                         interrupts = <2 24>;
  23                         clocks = <&clk_core>;
  24 -                       dmas = <&dma 13>,
  25 -                              <&dma 13>;
  26 -                       dma-names = "tx", "rx";
  27 +                       dmas = <&dma 13>;
  28 +                       dma-names = "rx-tx";
  29                         brcm,overclock-50 = <0>;
  30                         brcm,pio-limit = <1>;
  31                         status = "disabled";
  32 --- a/drivers/mmc/host/bcm2835-sdhost.c
  33 +++ b/drivers/mmc/host/bcm2835-sdhost.c
  34 @@ -185,9 +185,10 @@ struct bcm2835_host {
  35         unsigned int                    debug:1;                /* Enable debug output */
  36
  37         /*DMA part*/
  38 -       struct dma_chan                 *dma_chan_rx;           /* DMA channel for reads */
  39 -       struct dma_chan                 *dma_chan_tx;           /* DMA channel for writes */
  40 -       struct dma_chan                 *dma_chan;              /* Channel in used */
  41 +       struct dma_chan                 *dma_chan_rxtx;         /* DMA channel for reads and writes */
  42 +       struct dma_chan                 *dma_chan;              /* Channel in use */
  43 +       struct dma_slave_config         dma_cfg_rx;
  44 +       struct dma_slave_config         dma_cfg_tx;
  45         struct dma_async_tx_descriptor  *dma_desc;
  46         u32                             dma_dir;
  47         u32                             drain_words;
  48 @@ -771,12 +772,11 @@ static void bcm2835_sdhost_prepare_dma(s
  49         log_event("PRD<", (u32)data, 0);
  50         pr_debug("bcm2835_sdhost_prepare_dma()\n");
  51
  52 +       dma_chan = host->dma_chan_rxtx;
  53         if (data->flags & MMC_DATA_READ) {
  54 -               dma_chan = host->dma_chan_rx;
  55                 dir_data = DMA_FROM_DEVICE;
  56                 dir_slave = DMA_DEV_TO_MEM;
  57         } else {
  58 -               dma_chan = host->dma_chan_tx;
  59                 dir_data = DMA_TO_DEVICE;
  60                 dir_slave = DMA_MEM_TO_DEV;
  61         }
  62 @@ -813,6 +813,12 @@ static void bcm2835_sdhost_prepare_dma(s
  63                 host->drain_words = len/4;
  64         }
  65
  66 +       /* The parameters have already been validated, so this will not fail */
  67 +       (void)dmaengine_slave_config(dma_chan,
  68 +                                    (dir_data == DMA_FROM_DEVICE) ?
  69 +                                    &host->dma_cfg_rx :
  70 +                                    &host->dma_cfg_tx);
  71 +
  72         len = dma_map_sg(dma_chan->device->dev, data->sg, data->sg_len,
  73                          dir_data);
  74
  75 @@ -1805,28 +1811,46 @@ int bcm2835_sdhost_add_host(struct bcm28
  76         spin_lock_init(&host->lock);
  77
  78         if (host->allow_dma) {
  79 -               if (IS_ERR_OR_NULL(host->dma_chan_tx) ||
  80 -                   IS_ERR_OR_NULL(host->dma_chan_rx)) {
  81 -                       pr_err("%s: unable to initialise DMA channels. "
  82 +               if (IS_ERR_OR_NULL(host->dma_chan_rxtx)) {
  83 +                       pr_err("%s: unable to initialise DMA channel. "
  84                                "Falling back to PIO\n",
  85                                mmc_hostname(mmc));
  86                         host->use_dma = false;
  87                 } else {
  88 -                       host->use_dma = true;
  89 -
  90                         cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
  91                         cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
  92                         cfg.slave_id = 13;              /* DREQ channel */
  93
  94 +                       /* Validate the slave configurations */
  95 +
  96                         cfg.direction = DMA_MEM_TO_DEV;
  97                         cfg.src_addr = 0;
  98                         cfg.dst_addr = host->bus_addr + SDDATA;
  99 -                       ret = dmaengine_slave_config(host->dma_chan_tx, &cfg);
 100
 101 -                       cfg.direction = DMA_DEV_TO_MEM;
 102 -                       cfg.src_addr = host->bus_addr + SDDATA;
 103 -                       cfg.dst_addr = 0;
 104 -                       ret = dmaengine_slave_config(host->dma_chan_rx, &cfg);
 105 +                       ret = dmaengine_slave_config(host->dma_chan_rxtx, &cfg);
 106 +
 107 +                       if (ret == 0) {
 108 +                               host->dma_cfg_tx = cfg;
 109 +
 110 +                               cfg.direction = DMA_DEV_TO_MEM;
 111 +                               cfg.src_addr = host->bus_addr + SDDATA;
 112 +                               cfg.dst_addr = 0;
 113 +
 114 +                               ret = dmaengine_slave_config(host->dma_chan_rxtx, &cfg);
 115 +                       }
 116 +
 117 +                       if (ret == 0) {
 118 +                               host->dma_cfg_rx = cfg;
 119 +
 120 +                               host->use_dma = true;
 121 +                       } else {
 122 +                               pr_err("%s: unable to configure DMA channel. "
 123 +                                      "Falling back to PIO\n",
 124 +                                      mmc_hostname(mmc));
 125 +                               dma_release_channel(host->dma_chan_rxtx);
 126 +                               host->dma_chan_rxtx = NULL;
 127 +                               host->use_dma = false;
 128 +                       }
 129                 }
 130         } else {
 131                 host->use_dma = false;
 132 @@ -1948,19 +1972,21 @@ static int bcm2835_sdhost_probe(struct p
 133
 134         if (host->allow_dma) {
 135                 if (node) {
 136 -                       host->dma_chan_tx =
 137 -                               dma_request_slave_channel(dev, "tx");
 138 -                       host->dma_chan_rx =
 139 -                               dma_request_slave_channel(dev, "rx");
 140 +                       host->dma_chan_rxtx =
 141 +                               dma_request_slave_channel(dev, "rx-tx");
 142 +                       if (!host->dma_chan_rxtx)
 143 +                               host->dma_chan_rxtx =
 144 +                                       dma_request_slave_channel(dev, "tx");
 145 +                       if (!host->dma_chan_rxtx)
 146 +                               host->dma_chan_rxtx =
 147 +                                       dma_request_slave_channel(dev, "rx");
 148                 } else {
 149                         dma_cap_mask_t mask;
 150
 151                         dma_cap_zero(mask);
 152                         /* we don't care about the channel, any would work */
 153                         dma_cap_set(DMA_SLAVE, mask);
 154 -                       host->dma_chan_tx =
 155 -                               dma_request_channel(mask, NULL, NULL);
 156 -                       host->dma_chan_rx =
 157 +                       host->dma_chan_rxtx =
 158                                 dma_request_channel(mask, NULL, NULL);
 159                 }
 160         }