VC4's DSI1 has a bug where the AXI connection is broken for 32-bit
writes from the CPU, so we use the DMA engine to DMA 32-bit values
into registers instead. That sleeps, so we can't do it from the top
half.
As a solution, use an interrupt thread so that all our writes happen
when sleeping is is allowed.
v2: Use IRQF_ONESHOT (suggested by Boris)
Signed-off-by: Eric Anholt <e...@anholt.net>
---
Boris, that cleanup ended up working and it looks great. Thanks!
drivers/gpu/drm/vc4/vc4_dsi.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 554605af344e..3b74fda5662d 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -1360,6 +1360,25 @@ static void dsi_handle_error(struct vc4_dsi *dsi,
*ret = IRQ_HANDLED;
}
+/* Initial handler for port 1 where we need the reg_dma workaround.
+ * The register DMA writes sleep, so we can't do it in the top half.
+ * Instead we use IRQF_ONESHOT so that the IRQ gets disabled in the
+ * parent interrupt contrller until our interrupt thread is done.
+ */
+static irqreturn_t vc4_dsi_irq_defer_to_thread_handler(int irq, void *data)
+{
+ struct vc4_dsi *dsi = data;
+ u32 stat = DSI_PORT_READ(INT_STAT);
+
+ if (!stat)
+ return IRQ_NONE;
+
+ return IRQ_WAKE_THREAD;
+}
+
+/* Normal IRQ handler for port 0, or the threaded IRQ handler for port
+ * 1 where we need the reg_dma workaround.
+ */
static irqreturn_t vc4_dsi_irq_handler(int irq, void *data)
{
struct vc4_dsi *dsi = data;
@@ -1539,8 +1558,16 @@ static int vc4_dsi_bind(struct device *dev, struct
device *master, void *data)
/* Clear any existing interrupt state. */
DSI_PORT_WRITE(INT_STAT, DSI_PORT_READ(INT_STAT));
- ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
- vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
+ if (dsi->reg_dma_mem) {
+ ret = devm_request_threaded_irq(dev, platform_get_irq(pdev, 0),
+
vc4_dsi_irq_defer_to_thread_handler,
+ vc4_dsi_irq_handler,
+ IRQF_ONESHOT,
+ "vc4 dsi", dsi);
+ } else {
+ ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
+ vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
+ }
if (ret) {
if (ret != -EPROBE_DEFER)
dev_err(dev, "Failed to get interrupt: %d\n", ret);
--
2.14.2
