[PATCH 05/11] dmaengine: stm32-dma3: prevent LL refactoring thanks to DT configuration

Amelie Delaunay
2024-10-10T14:31:48Z

stm32-dma3 driver refactors the linked-list in order to address the memory
with the highest possible data width.
It means that it can introduce up to 2 linked-list items. One with a
transfer length multiple of channel maximum burst length and so with the
highest possible data width. And an extra one with the latest bytes, with
lower data width.
Some devices (e.g. FMC ECC) don't support having several transfers instead
of only one.
So add the possibility to prevent linked-list refactoring, when bit 17 of
the 'DMA transfer requirements' bit mask is set in device tree.
When NOPACK feature is used (bit 16 pf the 'DMA transfer requirements' bit
mask in device tree), linked-list refactoring can be avoided, since the
memory data width and burst will be aligned with the device ones.

Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
---
drivers/dma/stm32/stm32-dma3.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/dma/stm32/stm32-dma3.c b/drivers/dma/stm32/stm32-dma3.c
index 8cb112dc5e057d4832ca7e8bb38c548ae7e269c3..1467308dd27c4674b13d2740c05087b1338fd91a 100644
--- a/drivers/dma/stm32/stm32-dma3.c
+++ b/drivers/dma/stm32/stm32-dma3.c
@@ -222,6 +222,7 @@ enum stm32_dma3_port_data_width {
#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 */
+#define STM32_DMA3_DT_NOREFACT BIT(17)

/* struct stm32_dma3_chan .config_set bitfield */
#define STM32_DMA3_CFG_SET_DT BIT(0)
@@ -1126,10 +1127,13 @@ static void stm32_dma3_free_chan_resources(struct dma_chan *c)
chan->config_set = 0;
}

-static u32 stm32_dma3_get_ll_count(struct stm32_dma3_chan *chan, size_t len)
+static u32 stm32_dma3_get_ll_count(struct stm32_dma3_chan *chan, size_t len, bool prevent_refactor)
{
u32 count;

+ if (prevent_refactor)
+ return DIV_ROUND_UP(len, STM32_DMA3_MAX_BLOCK_SIZE);
+
count = len / STM32_DMA3_MAX_BLOCK_SIZE;
len -= (len / STM32_DMA3_MAX_BLOCK_SIZE) * STM32_DMA3_MAX_BLOCK_SIZE;

@@ -1179,8 +1183,10 @@ static struct dma_async_tx_descriptor *stm32_dma3_prep_dma_memcpy(struct dma_cha
struct stm32_dma3_swdesc *swdesc;
size_t next_size, offset;
u32 count, i, ctr1, ctr2;
+ bool prevent_refactor = !!FIELD_GET(STM32_DMA3_DT_NOPACK, chan->dt_config.tr_conf) ||
+ !!FIELD_GET(STM32_DMA3_DT_NOREFACT, chan->dt_config.tr_conf);

- count = stm32_dma3_get_ll_count(chan, len);
+ count = stm32_dma3_get_ll_count(chan, len, prevent_refactor);

swdesc = stm32_dma3_chan_desc_alloc(chan, count);
if (!swdesc)
@@ -1196,7 +1202,8 @@ static struct dma_async_tx_descriptor *stm32_dma3_prep_dma_memcpy(struct dma_cha
remaining = len - offset;
next_size = min_t(size_t, remaining, STM32_DMA3_MAX_BLOCK_SIZE);

- if (next_size < STM32_DMA3_MAX_BLOCK_SIZE && next_size >= chan->max_burst)
+ if (!prevent_refactor &&
+ (next_size < STM32_DMA3_MAX_BLOCK_SIZE && next_size >= chan->max_burst))
next_size = chan->max_burst * (remaining / chan->max_burst);

ret = stm32_dma3_chan_prep_hw(chan, DMA_MEM_TO_MEM, &swdesc->ccr, &ctr1, &ctr2,
@@ -1235,11 +1242,13 @@ static struct dma_async_tx_descriptor *stm32_dma3_prep_slave_sg(struct dma_chan
size_t len;
dma_addr_t sg_addr, dev_addr, src, dst;
u32 i, j, count, ctr1, ctr2;
+ bool prevent_refactor = !!FIELD_GET(STM32_DMA3_DT_NOPACK, chan->dt_config.tr_conf) ||
+ !!FIELD_GET(STM32_DMA3_DT_NOREFACT, chan->dt_config.tr_conf);
int ret;

count = 0;
for_each_sg(sgl, sg, sg_len, i)
- count += stm32_dma3_get_ll_count(chan, sg_dma_len(sg));
+ count += stm32_dma3_get_ll_count(chan, sg_dma_len(sg), prevent_refactor);

swdesc = stm32_dma3_chan_desc_alloc(chan, count);
if (!swdesc)
@@ -1256,7 +1265,8 @@ static struct dma_async_tx_descriptor *stm32_dma3_prep_slave_sg(struct dma_chan
do {
size_t chunk = min_t(size_t, len, STM32_DMA3_MAX_BLOCK_SIZE);

- if (chunk < STM32_DMA3_MAX_BLOCK_SIZE && chunk >= chan->max_burst)
+ if (!prevent_refactor &&
+ (chunk < STM32_DMA3_MAX_BLOCK_SIZE && chunk >= chan->max_burst))
chunk = chan->max_burst * (len / chan->max_burst);

if (dir == DMA_MEM_TO_DEV) {

--
2.25.1