spi-flash-dma.patch

   1 --- spi_bfin5xx.c       (revision 5493)
   2 +++ spi_bfin5xx.c       (working copy)
   3 @@ -619,6 +619,7 @@ static void pump_transfers(unsigned long
   4         struct spi_transfer *transfer = NULL;
   5         struct spi_transfer *previous = NULL;
   6         struct chip_data *chip = NULL;
   7 +       unsigned long flags;
   8         u8 width;
   9         u16 cr, dma_width, dma_config;
  10         u32 tranf_success = 1;
  11 @@ -766,7 +767,6 @@ static void pump_transfers(unsigned long
  12
  13                 disable_dma(drv_data->dma_channel);
  14                 clear_dma_irqstat(drv_data->dma_channel);
  15 -               bfin_spi_disable(drv_data);
  16
  17                 /* config dma channel */
  18                 dev_dbg(&drv_data->pdev->dev, "doing dma transfer\n");
  19 @@ -797,8 +797,7 @@ static void pump_transfers(unsigned long
  20                         enable_dma(drv_data->dma_channel);
  21
  22                         /* start SPI transfer */
  23 -                       write_CTRL(drv_data,
  24 -                               (cr | BIT_CTL_TIMOD_DMA_TX | BIT_CTL_ENABLE));
  25 +                       write_CTRL(drv_data, cr | BIT_CTL_TIMOD_DMA_TX);
  26
  27                         /* just return here, there can only be one transfer
  28                          * in this mode
  29 @@ -840,14 +839,22 @@ static void pump_transfers(unsigned long
  30                 } else
  31                         BUG();
  32
  33 -               /* start dma */
  34 -               dma_enable_irq(drv_data->dma_channel);
  35 -               set_dma_config(drv_data->dma_channel, dma_config);
  36 +               /* oh man, here there be monsters ... and i dont mean the
  37 +                * fluffy cute ones from pixar, i mean the kind that'll eat
  38 +                * your data, kick your dog, and love it all.  do *not* try
  39 +                * and change these lines unless you (1) heavily test DMA
  40 +                * with SPI flashes on a loaded system (e.g. ping floods),
  41 +                * (2) know just how broken the DMA engine interaction with
  42 +                * the SPI peripheral is, and (3) have someone else to blame
  43 +                * when you screw it all up anyways.
  44 +                */
  45                 set_dma_start_addr(drv_data->dma_channel, dma_start_addr);
  46 +               set_dma_config(drv_data->dma_channel, dma_config);
  47 +               local_irq_save(flags);
  48                 enable_dma(drv_data->dma_channel);
  49 -
  50 -               /* start SPI transfer */
  51 -               write_CTRL(drv_data, (cr | BIT_CTL_ENABLE));
  52 +               write_CTRL(drv_data, cr);
  53 +               dma_enable_irq(drv_data->dma_channel);
  54 +               local_irq_restore(flags);
  55
  56         } else {
  57                 /* IO mode write then read */