diff options
Diffstat (limited to 'target/linux/brcm2708/patches-4.4/0406-dmaengine-bcm2835-Fix-polling-for-completion-of-DMA-.patch')
| -rw-r--r-- | target/linux/brcm2708/patches-4.4/0406-dmaengine-bcm2835-Fix-polling-for-completion-of-DMA-.patch | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/target/linux/brcm2708/patches-4.4/0406-dmaengine-bcm2835-Fix-polling-for-completion-of-DMA-.patch b/target/linux/brcm2708/patches-4.4/0406-dmaengine-bcm2835-Fix-polling-for-completion-of-DMA-.patch new file mode 100644 index 0000000000..fdb812faa4 --- /dev/null +++ b/target/linux/brcm2708/patches-4.4/0406-dmaengine-bcm2835-Fix-polling-for-completion-of-DMA-.patch @@ -0,0 +1,68 @@ +From 42504be159b0fd85d705265dceec01c74d853478 Mon Sep 17 00:00:00 2001 +From: Eric Anholt <eric@anholt.net> +Date: Fri, 3 Jun 2016 19:29:11 -0700 +Subject: [PATCH] dmaengine: bcm2835: Fix polling for completion of DMA with + interrupts masked. + +The tx_status hook is supposed to be safe to call from interrupt +context, but it wouldn't ever return completion for the last transfer, +meaning you couldn't poll for DMA completion with interrupts masked. + +This fixes IRQ handling for bcm2835's DSI1, which requires using the +DMA engine to write its registers due to a bug in the AXI bridge. + +Signed-off-by: Eric Anholt <eric@anholt.net> +--- + drivers/dma/bcm2835-dma.c | 24 +++++++++++++++++++----- + 1 file changed, 19 insertions(+), 5 deletions(-) + +--- a/drivers/dma/bcm2835-dma.c ++++ b/drivers/dma/bcm2835-dma.c +@@ -588,16 +588,16 @@ static enum dma_status bcm2835_dma_tx_st + struct virt_dma_desc *vd; + enum dma_status ret; + unsigned long flags; ++ u32 residue; + + ret = dma_cookie_status(chan, cookie, txstate); +- if (ret == DMA_COMPLETE || !txstate) ++ if (ret == DMA_COMPLETE) + return ret; + + spin_lock_irqsave(&c->vc.lock, flags); + vd = vchan_find_desc(&c->vc, cookie); + if (vd) { +- txstate->residue = +- bcm2835_dma_desc_size(to_bcm2835_dma_desc(&vd->tx)); ++ residue = bcm2835_dma_desc_size(to_bcm2835_dma_desc(&vd->tx)); + } else if (c->desc && c->desc->vd.tx.cookie == cookie) { + struct bcm2835_desc *d = c->desc; + dma_addr_t pos; +@@ -609,11 +609,25 @@ static enum dma_status bcm2835_dma_tx_st + else + pos = 0; + +- txstate->residue = bcm2835_dma_desc_size_pos(d, pos); ++ residue = bcm2835_dma_desc_size_pos(d, pos); ++ ++ /* ++ * If our non-cyclic transfer is done, then report ++ * complete and trigger the next tx now. This lets ++ * the dmaengine API be used synchronously from an IRQ ++ * handler. ++ */ ++ if (!d->cyclic && residue == 0) { ++ vchan_cookie_complete(&c->desc->vd); ++ bcm2835_dma_start_desc(c); ++ ret = dma_cookie_status(chan, cookie, txstate); ++ } + } else { +- txstate->residue = 0; ++ residue = 0; + } + ++ dma_set_residue(txstate, residue); ++ + spin_unlock_irqrestore(&c->vc.lock, flags); + + return ret; |