[PATCH 4.19 319/321] dmaengine: stm32-dma: check whether length is aligned on FIFO threshold

Greg Kroah-Hartman
2019-12-03T22:59:42Z

From: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>

commit cc832dc8e32785a730ba07c3a357e17c201a5df8 upstream.

When a period length is not multiple of FIFO some data may be stuck
within FIFO.

Burst/FIFO Threshold/Period or buffer length check has to be hardened

In any case DMA will grant any request from client but will degraded
any parameters whether awkward.

Signed-off-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/dma/stm32-dma.c | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)

--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -308,20 +308,12 @@ static bool stm32_dma_fifo_threshold_is_

static bool stm32_dma_is_burst_possible(u32 buf_len, u32 threshold)
{
- switch (threshold) {
- case STM32_DMA_FIFO_THRESHOLD_FULL:
- if (buf_len >= STM32_DMA_MAX_BURST)
- return true;
- else
- return false;
- case STM32_DMA_FIFO_THRESHOLD_HALFFULL:
- if (buf_len >= STM32_DMA_MAX_BURST / 2)
- return true;
- else
- return false;
- default:
- return false;
- }
+ /*
+ * Buffer or period length has to be aligned on FIFO depth.
+ * Otherwise bytes may be stuck within FIFO at buffer or period
+ * length.
+ */
+ return ((buf_len % ((threshold + 1) * 4)) == 0);
}

static u32 stm32_dma_get_best_burst(u32 buf_len, u32 max_burst, u32 threshold,