diff options
| author | Amelie Delaunay <amelie.delaunay@foss.st.com> | 2024-10-16 14:39:54 +0200 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2024-10-21 22:51:44 +0530 |
| commit | 12eb621e1abff65d89aeb4c92a4f3436225971d0 (patch) | |
| tree | ead3caaa457b480b8e288f2992ac24c8bf8c8784 /drivers/dma/stm32/stm32-dma3.c | |
| parent | 689f05586e7ea620c8fc1066c067809e52ffc2f3 (diff) | |
dmaengine: stm32-dma3: prevent pack/unpack thanks to DT configuration
When source data width/burst and destination data width/burst are
different, data are packed or unpacked in DMA3 channel FIFO, using
CxTR1.PAM.
Data are pushed out from DMA3 channel FIFO when the destination burst
length (= data width * burst) is reached.
If the transfer is stopped before CxBR1.BNDT = 0, and if some bytes are
packed/unpacked in the DMA3 channel FIFO, these bytes are lost.
Indeed, DMA3 channel FIFO has no flush capability, only reset.
To avoid potential bytes lost, pack/unpack must be prevented by setting
memory data width/burst equal to peripheral data width/burst.
Memory accesses will be penalized. But it is the only way to avoid bytes
lost.
Prevent pack/unpack feature can be activated by setting bit 16 of DMA3
Transfer requirements bitfield (tr_conf) in device tree.
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20241016-dma3-mp25-updates-v3-2-8311fe6f228d@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma/stm32/stm32-dma3.c')
| -rw-r--r-- | drivers/dma/stm32/stm32-dma3.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/dma/stm32/stm32-dma3.c b/drivers/dma/stm32/stm32-dma3.c index b9470f783f98..f793eecd2c27 100644 --- a/drivers/dma/stm32/stm32-dma3.c +++ b/drivers/dma/stm32/stm32-dma3.c @@ -221,6 +221,7 @@ enum stm32_dma3_port_data_width { #define STM32_DMA3_DT_BREQ BIT(8) /* CTR2_BREQ */ #define STM32_DMA3_DT_PFREQ BIT(9) /* CTR2_PFREQ */ #define STM32_DMA3_DT_TCEM GENMASK(13, 12) /* CTR2_TCEM */ +#define STM32_DMA3_DT_NOPACK BIT(16) /* CTR1_PAM */ /* struct stm32_dma3_chan .config_set bitfield */ #define STM32_DMA3_CFG_SET_DT BIT(0) @@ -622,6 +623,10 @@ static int stm32_dma3_chan_prep_hw(struct stm32_dma3_chan *chan, enum dma_transf /* Set source (memory) data width and burst */ sdw = stm32_dma3_get_max_dw(chan->max_burst, sap_max_dw, len, src_addr); sbl_max = stm32_dma3_get_max_burst(len, sdw, chan->max_burst); + if (!!FIELD_GET(STM32_DMA3_DT_NOPACK, tr_conf)) { + sdw = ddw; + sbl_max = dbl_max; + } _ctr1 |= FIELD_PREP(CTR1_SDW_LOG2, ilog2(sdw)); _ctr1 |= FIELD_PREP(CTR1_SBL_1, sbl_max - 1); @@ -652,6 +657,11 @@ static int stm32_dma3_chan_prep_hw(struct stm32_dma3_chan *chan, enum dma_transf /* Set destination (memory) data width and burst */ ddw = stm32_dma3_get_max_dw(chan->max_burst, dap_max_dw, len, dst_addr); dbl_max = stm32_dma3_get_max_burst(len, ddw, chan->max_burst); + if (!!FIELD_GET(STM32_DMA3_DT_NOPACK, tr_conf) || + ((_ctr2 & CTR2_PFREQ) && ddw > sdw)) { /* Packing to wider ddw not supported */ + ddw = sdw; + dbl_max = sbl_max; + } _ctr1 |= FIELD_PREP(CTR1_SDW_LOG2, ilog2(sdw)); _ctr1 |= FIELD_PREP(CTR1_SBL_1, sbl_max - 1); |