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drm/vc4: Fix sleeps during the IRQ handler for DSI transactions. 

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)
v3: Style nitpicks.

Signed-off-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20171014001255.32005-1-eric@anholt.net
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com> (v2)
hifive-unleashed-5.1
Eric Anholt 2017-10-13 17:12:55 -07:00
parent b9f19259b8
commit af0c8c1056
1 changed files with 30 additions and 2 deletions
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32
drivers/gpu/drm/vc4/vc4_dsi.c
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@ -1360,6 +1360,27 @@ 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 +1560,15 @@ 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);