target/linux/brcm2708/patches-4.4/0176-bcm2835-mmc-Only-claim-one-DMA-channel.patch

   1 From af80d75abc7604cd9eb1788b0171148d000db09d Mon Sep 17 00:00:00 2001
   2 From: Phil Elwell <phil@raspberrypi.org>
   3 Date: Tue, 8 Mar 2016 09:49:16 +0000
   4 Subject: [PATCH 176/180] bcm2835-mmc: Only claim one DMA channel
   5
   6 With both MMC controllers enabled there are few DMA channels left. The
   7 bcm2835-mmc 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-mmc.c        | 69 +++++++++++++++++++++++++----------
  16  2 files changed, 51 insertions(+), 23 deletions(-)
  17
  18 --- a/arch/arm/boot/dts/bcm2708_common.dtsi
  19 +++ b/arch/arm/boot/dts/bcm2708_common.dtsi
  20 @@ -232,9 +232,8 @@
  21                         reg = <0x7e300000 0x100>;
  22                         interrupts = <2 30>;
  23                         clocks = <&clk_mmc>;
  24 -                       dmas = <&dma 11>,
  25 -                              <&dma 11>;
  26 -                       dma-names = "tx", "rx";
  27 +                       dmas = <&dma 11>;
  28 +                       dma-names = "rx-tx";
  29                         brcm,overclock-50 = <0>;
  30                         status = "disabled";
  31                 };
  32 --- a/drivers/mmc/host/bcm2835-mmc.c
  33 +++ b/drivers/mmc/host/bcm2835-mmc.c
  34 @@ -108,8 +108,9 @@ struct bcm2835_host {
  35         u32                                             shadow;
  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_rxtx;         /* DMA channel for reads and writes */
  41 +       struct dma_slave_config         dma_cfg_rx;
  42 +       struct dma_slave_config         dma_cfg_tx;
  43         struct dma_async_tx_descriptor  *tx_desc;       /* descriptor */
  44
  45         bool                                    have_dma;
  46 @@ -342,7 +343,7 @@ static void bcm2835_mmc_dma_complete(voi
  47
  48         if (host->data && !(host->data->flags & MMC_DATA_WRITE)) {
  49                 /* otherwise handled in SDHCI IRQ */
  50 -               dma_chan = host->dma_chan_rx;
  51 +               dma_chan = host->dma_chan_rxtx;
  52                 dir_data = DMA_FROM_DEVICE;
  53
  54                 dma_unmap_sg(dma_chan->device->dev,
  55 @@ -493,16 +494,21 @@ static void bcm2835_mmc_transfer_dma(str
  56         if (host->blocks == 0)
  57                 return;
  58
  59 +       dma_chan = host->dma_chan_rxtx;
  60         if (host->data->flags & MMC_DATA_READ) {
  61 -               dma_chan = host->dma_chan_rx;
  62                 dir_data = DMA_FROM_DEVICE;
  63                 dir_slave = DMA_DEV_TO_MEM;
  64         } else {
  65 -               dma_chan = host->dma_chan_tx;
  66                 dir_data = DMA_TO_DEVICE;
  67                 dir_slave = DMA_MEM_TO_DEV;
  68         }
  69
  70 +       /* The parameters have already been validated, so this will not fail */
  71 +       (void)dmaengine_slave_config(dma_chan,
  72 +                                    (dir_data == DMA_FROM_DEVICE) ?
  73 +                                    &host->dma_cfg_rx :
  74 +                                    &host->dma_cfg_tx);
  75 +
  76         BUG_ON(!dma_chan->device);
  77         BUG_ON(!dma_chan->device->dev);
  78         BUG_ON(!host->data->sg);
  79 @@ -936,7 +942,7 @@ static void bcm2835_mmc_data_irq(struct
  80                 if  (host->data->flags & MMC_DATA_WRITE) {
  81                         /* IRQ handled here */
  82
  83 -                       dma_chan = host->dma_chan_tx;
  84 +                       dma_chan = host->dma_chan_rxtx;
  85                         dir_data = DMA_TO_DEVICE;
  86                         dma_unmap_sg(dma_chan->device->dev,
  87                                  host->data->sg, host->data->sg_len,
  88 @@ -1316,28 +1322,47 @@ static int bcm2835_mmc_add_host(struct b
  89         dev_info(dev, "Forcing PIO mode\n");
  90         host->have_dma = false;
  91  #else
  92 -       if (IS_ERR_OR_NULL(host->dma_chan_tx) ||
  93 -           IS_ERR_OR_NULL(host->dma_chan_rx)) {
  94 -               dev_err(dev, "%s: Unable to initialise DMA channels. Falling back to PIO\n",
  95 +       if (IS_ERR_OR_NULL(host->dma_chan_rxtx)) {
  96 +               dev_err(dev, "%s: Unable to initialise DMA channel. Falling back to PIO\n",
  97                         DRIVER_NAME);
  98                 host->have_dma = false;
  99         } else {
 100 -               dev_info(dev, "DMA channels allocated");
 101 -               host->have_dma = true;
 102 +               dev_info(dev, "DMA channel allocated");
 103
 104                 cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 105                 cfg.dst_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
 106                 cfg.slave_id = 11;              /* DREQ channel */
 107
 108 +               /* Validate the slave configurations */
 109 +
 110                 cfg.direction = DMA_MEM_TO_DEV;
 111                 cfg.src_addr = 0;
 112                 cfg.dst_addr = host->bus_addr + SDHCI_BUFFER;
 113 -               ret = dmaengine_slave_config(host->dma_chan_tx, &cfg);
 114
 115 -               cfg.direction = DMA_DEV_TO_MEM;
 116 -               cfg.src_addr = host->bus_addr + SDHCI_BUFFER;
 117 -               cfg.dst_addr = 0;
 118 -               ret = dmaengine_slave_config(host->dma_chan_rx, &cfg);
 119 +               ret = dmaengine_slave_config(host->dma_chan_rxtx, &cfg);
 120 +
 121 +               if (ret == 0) {
 122 +                       host->dma_cfg_tx = cfg;
 123 +
 124 +                       cfg.direction = DMA_DEV_TO_MEM;
 125 +                       cfg.src_addr = host->bus_addr + SDHCI_BUFFER;
 126 +                       cfg.dst_addr = 0;
 127 +
 128 +                       ret = dmaengine_slave_config(host->dma_chan_rxtx, &cfg);
 129 +               }
 130 +
 131 +               if (ret == 0) {
 132 +                       host->dma_cfg_rx = cfg;
 133 +
 134 +                       host->use_dma = true;
 135 +               } else {
 136 +                       pr_err("%s: unable to configure DMA channel. "
 137 +                              "Faling back to PIO\n",
 138 +                              mmc_hostname(mmc));
 139 +                       dma_release_channel(host->dma_chan_rxtx);
 140 +                       host->dma_chan_rxtx = NULL;
 141 +                       host->use_dma = false;
 142 +               }
 143         }
 144  #endif
 145         mmc->max_segs = 128;
 146 @@ -1416,16 +1441,20 @@ static int bcm2835_mmc_probe(struct plat
 147
 148  #ifndef FORCE_PIO
 149         if (node) {
 150 -               host->dma_chan_tx = dma_request_slave_channel(dev, "tx");
 151 -               host->dma_chan_rx = dma_request_slave_channel(dev, "rx");
 152 +               host->dma_chan_rxtx = dma_request_slave_channel(dev, "rx-tx");
 153 +               if (!host->dma_chan_rxtx)
 154 +                       host->dma_chan_rxtx =
 155 +                               dma_request_slave_channel(dev, "tx");
 156 +               if (!host->dma_chan_rxtx)
 157 +                       host->dma_chan_rxtx =
 158 +                               dma_request_slave_channel(dev, "rx");
 159         } else {
 160                 dma_cap_mask_t mask;
 161
 162                 dma_cap_zero(mask);
 163                 /* we don't care about the channel, any would work */
 164                 dma_cap_set(DMA_SLAVE, mask);
 165 -               host->dma_chan_tx = dma_request_channel(mask, NULL, NULL);
 166 -               host->dma_chan_rx = dma_request_channel(mask, NULL, NULL);
 167 +               host->dma_chan_rxtx = dma_request_channel(mask, NULL, NULL);
 168         }
 169  #endif
 170         clk = devm_clk_get(dev, NULL);