diff mbox series

[v4,2/5] dmaengine: sun6i-dma: Support variable address widths using masks

Message ID 20260826-sun60i-a733-dma-v4-2-dc2f745f40dc@gmail.com (mailing list archive)
State New
Headers
Series dmaengine: sun6i-dma: Add support for Allwinner A733 DMA controller |

Commit Message

Yuanshen Cao Aug. 26, 2026, 1:30 a.m. UTC 
The Allwinner A733 DMA controller supports higher addresses (up to
32G) compared to previous generations. The existing `sun6i_dma_set_addr`
function uses hardcoded logic for setting the high-address bits in the
LLI parameters.

Add `src_high_addr_mask` and `dst_high_addr_mask` to `struct
sun6i_dma_config` to handle different high-address bitfield mappings.
Update `sun6i_dma_set_addr` to use these masks via `field_prep()`,
allowing the driver to support variable address widths.

Signed-off-by: Yuanshen Cao <alex.caoys@gmail.com>
---
 drivers/dma/sun6i-dma.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

Comments

sashiko-bot@kernel.org Aug. 26, 2026, 1:40 a.m. UTC | #1 
Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [Low] Local redefinition of standard kernel macros `field_get` and `field_prep` instead of using the generic implementations from `<linux/bitfield.h>`.
- [Low] The newly introduced `field_get` macro is never used.
--

commit f2482b50c417768080bd7de168d315dbd88b3be7
Author: Yuanshen Cao <alex.caoys@gmail.com>

dmaengine: sun6i-dma: Support variable address widths using masks

This patch updates sun6i_dma_set_addr() to use masks for high-address bits,
allowing the driver to support variable address widths for newer Allwinner
SoCs. It also introduces local field_get and field_prep macros.

> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index f305fbfb35453..53c54161e32a9 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -24,6 +24,10 @@
>  
>  #include "virt-dma.h"
>  
> +/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
> +#define field_get(_mask, _reg)	(((_reg) & (_mask)) >> (ffs(_mask) - 1))

[Severity: Low]
Is this macro actually needed?

Looking through the rest of the patch, field_get() doesn't seem to be used
anywhere.

> +#define field_prep(_mask, _val)	(((_val) << (ffs(_mask) - 1)) & (_mask))

[Severity: Low]
Could we use the generic implementations from <linux/bitfield.h> instead of
defining field_prep() and field_get() locally?

Redefining these core kernel macros creates a namespace collision, bypasses
the standard bitfield type-safety checks, and risks a build failure if
<linux/bitfield.h> is ever included in this driver.

Additionally, unlike the standard kernel macros, these custom versions
evaluate their arguments multiple times.
diff mbox series

Patch

diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
index f305fbfb3545..53c54161e32a 100644
--- a/drivers/dma/sun6i-dma.c
+++ b/drivers/dma/sun6i-dma.c
@@ -24,6 +24,10 @@ 
 
 #include "virt-dma.h"
 
+/* Non-constant mask variant of FIELD_GET() and FIELD_PREP() */
+#define field_get(_mask, _reg)	(((_reg) & (_mask)) >> (ffs(_mask) - 1))
+#define field_prep(_mask, _val)	(((_val) << (ffs(_mask) - 1)) & (_mask))
+
 /*
  * Common registers
  */
@@ -103,8 +107,8 @@ 
  * The LLI link physical address is also mangled, but we avoid dealing
  * with that by allocating LLIs from the DMA32 zone.
  */
-#define SRC_HIGH_ADDR(x)		(((x) & 0x3U) << 16)
-#define DST_HIGH_ADDR(x)		(((x) & 0x3U) << 18)
+#define SRC_HIGH_ADDR_MASK	GENMASK(17, 16)
+#define DST_HIGH_ADDR_MASK	GENMASK(19, 18)
 
 /*
  * Various hardware related defines
@@ -147,7 +151,8 @@  struct sun6i_dma_config {
 	u32 dst_burst_lengths;
 	u32 src_addr_widths;
 	u32 dst_addr_widths;
-	bool has_high_addr;
+	u32 src_high_addr_mask;
+	u32 dst_high_addr_mask;
 	bool has_mbus_clk;
 	u32 irq_stride;
 	u32 irq_en_offset;
@@ -687,9 +692,10 @@  static inline void sun6i_dma_set_addr(struct sun6i_dma_dev *sdev,
 	v_lli->src = lower_32_bits(src);
 	v_lli->dst = lower_32_bits(dst);
 
-	if (sdev->cfg->has_high_addr)
-		v_lli->para |= SRC_HIGH_ADDR(upper_32_bits(src)) |
-			       DST_HIGH_ADDR(upper_32_bits(dst));
+	if (sdev->cfg->src_high_addr_mask)
+		v_lli->para |=
+			field_prep(sdev->cfg->src_high_addr_mask, upper_32_bits(src)) |
+			field_prep(sdev->cfg->dst_high_addr_mask, upper_32_bits(dst));
 }
 
 static struct dma_async_tx_descriptor *sun6i_dma_prep_dma_memcpy(
@@ -1283,7 +1289,8 @@  static struct sun6i_dma_config sun50i_a100_dma_cfg = {
 			     BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
 			     BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) |
 			     BIT(DMA_SLAVE_BUSWIDTH_8_BYTES),
-	.has_high_addr = true,
+	.src_high_addr_mask = SRC_HIGH_ADDR_MASK,
+	.dst_high_addr_mask = DST_HIGH_ADDR_MASK,
 	.has_mbus_clk = true,
 	SUN6I_DMA_IRQ_A31_COMMON_CFG
 };