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Subject[RFC PATCH] dmaengine: sh: Correct src_addr_widths/dst_addr_widths bitmask setting
Date
Obviously, the current value for the burst widths are wrong, and if this
value is retrieved from some other subsystem using dma_get_slave_caps,
it will wrongly assume burst width of e.g. 3 bytes are supported.

Each bit in the bitmask corresponds to a supported width, but it uses
an encoding of BIT(<widths>), not BIT(log2<widths>), as it must be able
to encode a width of 3 bytes.

The corollary is, it is not possible to encode either a width of 32 or
64 bytes, as the field has a size of 32 bits, and only a subset of the
controller capabilities can be exposed.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
---
drivers/dma/sh/rcar-dmac.c | 14 ++++++++++----
drivers/dma/sh/shdmac.c | 13 +++++++++----
drivers/dma/sh/usb-dmac.c | 9 ++++++---
3 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
index 2b2c7db3e480..768076caccfd 100644
--- a/drivers/dma/sh/rcar-dmac.c
+++ b/drivers/dma/sh/rcar-dmac.c
@@ -1734,10 +1734,16 @@ static int rcar_dmac_parse_of(struct device *dev, struct rcar_dmac *dmac)

static int rcar_dmac_probe(struct platform_device *pdev)
{
- const enum dma_slave_buswidth widths = DMA_SLAVE_BUSWIDTH_1_BYTE |
- DMA_SLAVE_BUSWIDTH_2_BYTES | DMA_SLAVE_BUSWIDTH_4_BYTES |
- DMA_SLAVE_BUSWIDTH_8_BYTES | DMA_SLAVE_BUSWIDTH_16_BYTES |
- DMA_SLAVE_BUSWIDTH_32_BYTES | DMA_SLAVE_BUSWIDTH_64_BYTES;
+ /*
+ * FIXME: Controller supports DMA_SLAVE_BUSWIDTH_32_BYTES
+ * and DMA_SLAVE_BUSWIDTH_64_BYTES,
+ * but this overflows the u32 src/dst_addr_widths fields
+ */
+ const u32 widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
+ BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
+ BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) |
+ BIT(DMA_SLAVE_BUSWIDTH_8_BYTES) |
+ BIT(DMA_SLAVE_BUSWIDTH_16_BYTES);
unsigned int channels_offset = 0;
struct dma_device *engine;
struct rcar_dmac *dmac;
diff --git a/drivers/dma/sh/shdmac.c b/drivers/dma/sh/shdmac.c
index c94ffab0d25c..bf35b5588b11 100644
--- a/drivers/dma/sh/shdmac.c
+++ b/drivers/dma/sh/shdmac.c
@@ -679,10 +679,15 @@ MODULE_DEVICE_TABLE(of, sh_dmae_of_match);

static int sh_dmae_probe(struct platform_device *pdev)
{
- const enum dma_slave_buswidth widths =
- DMA_SLAVE_BUSWIDTH_1_BYTE | DMA_SLAVE_BUSWIDTH_2_BYTES |
- DMA_SLAVE_BUSWIDTH_4_BYTES | DMA_SLAVE_BUSWIDTH_8_BYTES |
- DMA_SLAVE_BUSWIDTH_16_BYTES | DMA_SLAVE_BUSWIDTH_32_BYTES;
+ /*
+ * FIXME: Controller supports DMA_SLAVE_BUSWIDTH_32_BYTES
+ * but this overflows the u32 src/dst_addr_widths fields
+ */
+ const u32 widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
+ BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
+ BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) |
+ BIT(DMA_SLAVE_BUSWIDTH_8_BYTES) |
+ BIT(DMA_SLAVE_BUSWIDTH_16_BYTES);
const struct sh_dmae_pdata *pdata;
unsigned long chan_flag[SH_DMAE_MAX_CHANNELS] = {};
int chan_irq[SH_DMAE_MAX_CHANNELS];
diff --git a/drivers/dma/sh/usb-dmac.c b/drivers/dma/sh/usb-dmac.c
index 31a145154e9f..0ac7e842b70c 100644
--- a/drivers/dma/sh/usb-dmac.c
+++ b/drivers/dma/sh/usb-dmac.c
@@ -768,7 +768,6 @@ static int usb_dmac_parse_of(struct device *dev, struct usb_dmac *dmac)

static int usb_dmac_probe(struct platform_device *pdev)
{
- const enum dma_slave_buswidth widths = USB_DMAC_SLAVE_BUSWIDTH;
struct dma_device *engine;
struct usb_dmac *dmac;
struct resource *mem;
@@ -837,8 +836,12 @@ static int usb_dmac_probe(struct platform_device *pdev)

engine->dev = &pdev->dev;

- engine->src_addr_widths = widths;
- engine->dst_addr_widths = widths;
+ /*
+ * FIXME: The controller supports a width of USB_DMAC_SLAVE_BUSWIDTH,
+ * i.e. 32 bytes, but BIT(32) overflows the u32 bitmask fields.
+ */
+ engine->src_addr_widths = 0;
+ engine->dst_addr_widths = 0;
engine->directions = BIT(DMA_MEM_TO_DEV) | BIT(DMA_DEV_TO_MEM);
engine->residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;

--
2.14.1
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