target/linux/brcm2708/patches-4.14/950-0176-drm-vc4-Fix-sleeps-during-the-IRQ-handler-for-DSI-tr.patch

   1 From 659c52fe8a86264c5119c0592654898d09fe8f28 Mon Sep 17 00:00:00 2001
   2 From: Eric Anholt <eric@anholt.net>
   3 Date: Fri, 13 Oct 2017 17:12:55 -0700
   4 Subject: [PATCH 176/454] drm/vc4: Fix sleeps during the IRQ handler for DSI
   5  transactions.
   6
   7 VC4's DSI1 has a bug where the AXI connection is broken for 32-bit
   8 writes from the CPU, so we use the DMA engine to DMA 32-bit values
   9 into registers instead.  That sleeps, so we can't do it from the top
  10 half.
  11
  12 As a solution, use an interrupt thread so that all our writes happen
  13 when sleeping is is allowed.
  14
  15 v2: Use IRQF_ONESHOT (suggested by Boris)
  16 v3: Style nitpicks.
  17
  18 Signed-off-by: Eric Anholt <eric@anholt.net>
  19 Link: https://patchwork.freedesktop.org/patch/msgid/20171014001255.32005-1-eric@anholt.net
  20 Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v2)
  21 (cherry picked from commit af0c8c10564aac5b6d67308129ec09c4ad5db476)
  22 ---
  23  drivers/gpu/drm/vc4/vc4_dsi.c | 32 ++++++++++++++++++++++++++++++--
  24  1 file changed, 30 insertions(+), 2 deletions(-)
  25
  26 --- a/drivers/gpu/drm/vc4/vc4_dsi.c
  27 +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
  28 @@ -1383,6 +1383,27 @@ static void dsi_handle_error(struct vc4_
  29         *ret = IRQ_HANDLED;
  30  }
  31
  32 +/*
  33 + * Initial handler for port 1 where we need the reg_dma workaround.
  34 + * The register DMA writes sleep, so we can't do it in the top half.
  35 + * Instead we use IRQF_ONESHOT so that the IRQ gets disabled in the
  36 + * parent interrupt contrller until our interrupt thread is done.
  37 + */
  38 +static irqreturn_t vc4_dsi_irq_defer_to_thread_handler(int irq, void *data)
  39 +{
  40 +       struct vc4_dsi *dsi = data;
  41 +       u32 stat = DSI_PORT_READ(INT_STAT);
  42 +
  43 +       if (!stat)
  44 +               return IRQ_NONE;
  45 +
  46 +       return IRQ_WAKE_THREAD;
  47 +}
  48 +
  49 +/*
  50 + * Normal IRQ handler for port 0, or the threaded IRQ handler for port
  51 + * 1 where we need the reg_dma workaround.
  52 + */
  53  static irqreturn_t vc4_dsi_irq_handler(int irq, void *data)
  54  {
  55         struct vc4_dsi *dsi = data;
  56 @@ -1566,8 +1587,15 @@ static int vc4_dsi_bind(struct device *d
  57         /* Clear any existing interrupt state. */
  58         DSI_PORT_WRITE(INT_STAT, DSI_PORT_READ(INT_STAT));
  59
  60 -       ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
  61 -                              vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
  62 +       if (dsi->reg_dma_mem)
  63 +               ret = devm_request_threaded_irq(dev, platform_get_irq(pdev, 0),
  64 +                                               vc4_dsi_irq_defer_to_thread_handler,
  65 +                                               vc4_dsi_irq_handler,
  66 +                                               IRQF_ONESHOT,
  67 +                                               "vc4 dsi", dsi);
  68 +       else
  69 +               ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
  70 +                                      vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
  71         if (ret) {
  72                 if (ret != -EPROBE_DEFER)
  73                         dev_err(dev, "Failed to get interrupt: %d\n", ret);