2018-09-11 07:32:07

by Pierre-Yves MORDRET

Subject: [PATCH v1 1/1] dmaengine: stm32-dma: check whether length is aligned on FIFO threshold

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 <[email protected]>
---
Version history:
v1:
* Initial
---
---
drivers/dma/stm32-dma.c | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 379e8d5..4903a40 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -308,20 +308,12 @@ static bool stm32_dma_fifo_threshold_is_allowed(u32 burst, u32 threshold,

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,
--
2.7.4

2018-10-02 15:02:59

by Vinod Koul

Subject: Re: [PATCH v1 1/1] dmaengine: stm32-dma: check whether length is aligned on FIFO threshold

On 11-09-18, 09:31, Pierre-Yves MORDRET wrote:
> 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.

Applied, thanks

--
~Vinod