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media: bcm2835-unicam: Fix bug in buffer swapping logic #4189

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merged 1 commit into from
Mar 5, 2021
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media: bcm2835-unicam: Fix bug in buffer swapping logic #4189

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21 changes: 18 additions & 3 deletions drivers/media/platform/bcm2835/bcm2835-unicam.c
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Original file line number Diff line number Diff line change
Expand Up @@ -798,6 +798,7 @@ static irqreturn_t unicam_isr(int irq, void *dev)
unsigned int sequence = unicam->sequence;
unsigned int i;
u32 ista, sta;
bool fe;
u64 ts;

sta = reg_read(unicam, UNICAM_STA);
Expand All @@ -814,13 +815,19 @@ static irqreturn_t unicam_isr(int irq, void *dev)
if (!(sta & (UNICAM_IS | UNICAM_PI0)))
return IRQ_HANDLED;

/*
* Look for either the Frame End interrupt or the Packet Capture status
* to signal a frame end.
*/
fe = (ista & UNICAM_FEI || sta & UNICAM_PI0);

/*
* We must run the frame end handler first. If we have a valid next_frm
* and we get a simultaneout FE + FS interrupt, running the FS handler
* first would null out the next_frm ptr and we would have lost the
* buffer forever.
*/
if (ista & UNICAM_FEI || sta & UNICAM_PI0) {
if (fe) {
/*
* Ensure we have swapped buffers already as we can't
* stop the peripheral. If no buffer is available, use a
Expand All @@ -831,7 +838,15 @@ static irqreturn_t unicam_isr(int irq, void *dev)
if (!unicam->node[i].streaming)
continue;

if (unicam->node[i].cur_frm)
/*
* If cur_frm == next_frm, it means we have not had
* a chance to swap buffers, likely due to having
* multiple interrupts occurring simultaneously (like FE
* + FS + LS). In this case, we cannot signal the buffer
* as complete, as the HW will reuse that buffer.
*/
if (unicam->node[i].cur_frm &&
unicam->node[i].cur_frm != unicam->node[i].next_frm)
unicam_process_buffer_complete(&unicam->node[i],
sequence);
unicam->node[i].cur_frm = unicam->node[i].next_frm;
Expand Down Expand Up @@ -868,7 +883,7 @@ static irqreturn_t unicam_isr(int irq, void *dev)
* where the HW does not actually swap it if the new frame has
* already started.
*/
if (ista & (UNICAM_FSI | UNICAM_LCI) && !(ista & UNICAM_FEI)) {
if (ista & (UNICAM_FSI | UNICAM_LCI) && !fe) {
for (i = 0; i < ARRAY_SIZE(unicam->node); i++) {
if (!unicam->node[i].streaming)
continue;
Expand Down