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 <[email protected]> --- 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
