@@ -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);
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> --- drivers/dma/stm32/stm32-dma3.c | 10 ++++++++++ 1 file changed, 10 insertions(+)