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media: apple: avd: Do not pop an empty mailbox #640

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media: apple: avd: Do not pop an empty mailbox #640

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20 changes: 20 additions & 0 deletions drivers/media/platform/apple/avd/avd-drv.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@
#include <linux/iommu.h>
#include <linux/reset.h>
#include <linux/delay.h>
#include <linux/iopoll.h>

#include <media/videobuf2-dma-contig.h>
#include <media/videobuf2-v4l2.h>
Expand Down Expand Up @@ -300,6 +301,25 @@ static irqreturn_t avd_irq_handler(int irq, void *data)
if (!ctx)
return IRQ_HANDLED;

/*
* Only pop a message the mailbox holds: popping an empty mailbox returns
* the previous message again. A stale post-processing "done" read that
* way finishes the frame early, the next frame starts while the PP is
* still busy, and its PP never completes, so the watchdog resets the
* decoder and the stream fails. The interrupt can also arrive just before
* its message is readable, so give the message a moment first.
*/
if (readl(avd->mbox + AVD_REG_MBOX1_STATUS) & AVD_MBOX1_STATUS_EMPTY) {
u32 mb;

if (readl_poll_timeout_atomic(avd->mbox + AVD_REG_MBOX1_STATUS, mb,
!(mb & AVD_MBOX1_STATUS_EMPTY), 1, 10)) {
dev_dbg(avd->dev, "spurious interrupt, mailbox empty\n");
writel(AVD_MBOX1_NOT_EMPTY, avd->mbox + AVD_REG_MBOX_IRQ_CLR);
return IRQ_HANDLED;
}
}

status = readl(avd->mbox + AVD_REG_MBOX1_RETRIEVE);

writel(AVD_MBOX1_NOT_EMPTY, avd->mbox + AVD_REG_MBOX_IRQ_CLR);
Expand Down
2 changes: 2 additions & 0 deletions drivers/media/platform/apple/avd/avd-regs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,8 @@
#define AVD_MBOX1_NOT_EMPTY BIT(3)

#define AVD_REG_MBOX1_STATUS 0x5c
/* Read side: bits 8-11 write pointer, bits 12-15 read pointer, bit 17 empty. */
#define AVD_MBOX1_STATUS_EMPTY BIT(17)
#define AVD_REG_MBOX1_RETRIEVE 0x64
#define AVD_MBOX_ENABLE BIT(0)

Expand Down