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 (suggested by Arnd), we can mask the IRQ in the irqchip
in the top half, and re-enable it from an irqthread.
Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
---
drivers/gpu/drm/vc4/vc4_dsi.c | 39 +++++++++++++++++++++++++++++++++++++--
1 file changed, 37 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index ec1d646b3151..9556236b67d0 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -516,6 +516,8 @@ struct vc4_dsi {
/* Whether we're on bcm2835's DSI0 or DSI1. */
int port;
+ int irq;
+
/* DSI channel for the panel we're connected to. */
u32 channel;
u32 lanes;
@@ -1360,6 +1362,28 @@ 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 just disable the interrupt in the only way we have
+ * available (mask it in the irqchip), and continue on to the threaded
+ * handler.
+ */
+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;
+
+ disable_irq_nosync(dsi->irq);
+
+ 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;
@@ -1368,6 +1392,9 @@ static irqreturn_t vc4_dsi_irq_handler(int irq, void *data)
DSI_PORT_WRITE(INT_STAT, stat);
+ if (dsi->reg_dma_mem)
+ enable_irq(dsi->irq);
+
dsi_handle_error(dsi, &ret, stat,
DSI1_INT_ERR_SYNC_ESC, "LPDT sync");
dsi_handle_error(dsi, &ret, stat,
@@ -1539,8 +1566,16 @@ 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);
+ dsi->irq = platform_get_irq(pdev, 0);
+ if (dsi->reg_dma_mem) {
+ ret = devm_request_threaded_irq(dev, dsi->irq,
+ vc4_dsi_irq_defer_to_thread_handler,
+ vc4_dsi_irq_handler, 0,
+ "vc4 dsi", dsi);
+ } else {
+ ret = devm_request_irq(dev, dsi->irq,
+ vc4_dsi_irq_handler, 0, "vc4 dsi", dsi);
+ }
if (ret) {
if (ret != -EPROBE_DEFER)
dev_err(dev, "Failed to get interrupt: %d\n", ret);
--
2.14.1
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