[PATCH 3.16 204/328] spi: rspi: Fix leaking of unused DMA descriptors

Ben Hutchings
2018-12-09T22:13:50Z

From: Geert Uytterhoeven <geert+renesas@glider.be>

commit 3819bc8752367eae0d72fa1c473dc88ea45631a7 upstream.

If dmaengine_prep_slave_sg() or dmaengine_submit() fail, we may leak
unused DMA descriptors.

As per Documentation/dmaengine.txt, once a DMA descriptor has been
obtained, it must be submitted. Hence:
- First prepare and submit all DMA descriptors,
- Prepare the SPI controller for DMA,
- Start DMA by calling dma_async_issue_pending(),
- Make sure to call dmaengine_terminate_all() on all descriptors that
haven't completed.

Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@linaro.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
drivers/spi/spi-rspi.c | 94 ++++++++++++++++++++++++++----------------
1 file changed, 58 insertions(+), 36 deletions(-)

--- a/drivers/spi/spi-rspi.c
+++ b/drivers/spi/spi-rspi.c
@@ -472,25 +472,52 @@ static int rspi_dma_transfer(struct rspi
dma_cookie_t cookie;
int ret;

- if (tx) {
- desc_tx = dmaengine_prep_slave_sg(rspi->master->dma_tx,
- tx->sgl, tx->nents, DMA_TO_DEVICE,
- DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
- if (!desc_tx)
- goto no_dma;
-
- irq_mask |= SPCR_SPTIE;
- }
+ /* First prepare and submit the DMA request(s), as this may fail */
if (rx) {
desc_rx = dmaengine_prep_slave_sg(rspi->master->dma_rx,
rx->sgl, rx->nents, DMA_FROM_DEVICE,
DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
- if (!desc_rx)
- goto no_dma;
+ if (!desc_rx) {
+ ret = -EAGAIN;
+ goto no_dma_rx;
+ }
+
+ desc_rx->callback = rspi_dma_complete;
+ desc_rx->callback_param = rspi;
+ cookie = dmaengine_submit(desc_rx);
+ if (dma_submit_error(cookie)) {
+ ret = cookie;
+ goto no_dma_rx;
+ }

irq_mask |= SPCR_SPRIE;
}

+ if (tx) {
+ desc_tx = dmaengine_prep_slave_sg(rspi->master->dma_tx,
+ tx->sgl, tx->nents, DMA_TO_DEVICE,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!desc_tx) {
+ ret = -EAGAIN;
+ goto no_dma_tx;
+ }
+
+ if (rx) {
+ /* No callback */
+ desc_tx->callback = NULL;
+ } else {
+ desc_tx->callback = rspi_dma_complete;
+ desc_tx->callback_param = rspi;
+ }
+ cookie = dmaengine_submit(desc_tx);
+ if (dma_submit_error(cookie)) {
+ ret = cookie;
+ goto no_dma_tx;
+ }
+
+ irq_mask |= SPCR_SPTIE;
+ }
+
/*
* DMAC needs SPxIE, but if SPxIE is set, the IRQ routine will be
* called. So, this driver disables the IRQ while DMA transfer.
@@ -503,34 +530,24 @@ static int rspi_dma_transfer(struct rspi
rspi_enable_irq(rspi, irq_mask);
rspi->dma_callbacked = 0;

- if (rx) {
- desc_rx->callback = rspi_dma_complete;
- desc_rx->callback_param = rspi;
- cookie = dmaengine_submit(desc_rx);
- if (dma_submit_error(cookie))
- return cookie;
+ /* Now start DMA */
+ if (rx)
dma_async_issue_pending(rspi->master->dma_rx);
- }
- if (tx) {
- if (rx) {
- /* No callback */
- desc_tx->callback = NULL;
- } else {
- desc_tx->callback = rspi_dma_complete;
- desc_tx->callback_param = rspi;
- }
- cookie = dmaengine_submit(desc_tx);
- if (dma_submit_error(cookie))
- return cookie;
+ if (tx)
dma_async_issue_pending(rspi->master->dma_tx);
- }

ret = wait_event_interruptible_timeout(rspi->wait,
rspi->dma_callbacked, HZ);
if (ret > 0 && rspi->dma_callbacked)
ret = 0;
- else if (!ret)
+ else if (!ret) {
+ dev_err(&rspi->master->dev, "DMA timeout\n");
ret = -ETIMEDOUT;
+ if (tx)
+ dmaengine_terminate_all(rspi->master->dma_tx);
+ if (rx)
+ dmaengine_terminate_all(rspi->master->dma_rx);
+ }

rspi_disable_irq(rspi, irq_mask);

@@ -541,11 +558,16 @@ static int rspi_dma_transfer(struct rspi

return ret;

-no_dma:
- pr_warn_once("%s %s: DMA not available, falling back to PIO\n",
- dev_driver_string(&rspi->master->dev),
- dev_name(&rspi->master->dev));
- return -EAGAIN;
+no_dma_tx:
+ if (rx)
+ dmaengine_terminate_all(rspi->master->dma_rx);
+no_dma_rx:
+ if (ret == -EAGAIN) {
+ pr_warn_once("%s %s: DMA not available, falling back to PIO\n",
+ dev_driver_string(&rspi->master->dev),
+ dev_name(&rspi->master->dev));
+ }
+ return ret;
}

static void rspi_receive_init(const struct rspi_data *rspi)