[PATCH] dmaengine: vdma: Add 64 bit addressing support to the driver

Laurent Pinchart
2015-08-18T22:43:47Z

Hi Anurag,

Thank you for the patch.

On Wednesday 05 August 2015 17:17:37 Anurag Kumar Vulisha wrote:
> This patch adds the 64 bit addressing support to the vdma driver.
>
> Signed-off-by: Anurag Kumar Vulisha <anuragku@xilinx.com>
> ---
> drivers/dma/Kconfig | 2 +-
> drivers/dma/xilinx/xilinx_vdma.c | 36 ++++++++++++++++++++++++++++------
> 2 files changed, 31 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
> index bda2cb0..a7cd0a8 100644
> --- a/drivers/dma/Kconfig
> +++ b/drivers/dma/Kconfig
> @@ -398,7 +398,7 @@ config FSL_EDMA
>
> config XILINX_VDMA
> tristate "Xilinx AXI VDMA Engine"
> - depends on (ARCH_ZYNQ || MICROBLAZE)
> + depends on (ARCH_ZYNQ || MICROBLAZE || ARM64)
> select DMA_ENGINE
> help
> Enable support for Xilinx AXI VDMA Soft IP.
> diff --git a/drivers/dma/xilinx/xilinx_vdma.c
> b/drivers/dma/xilinx/xilinx_vdma.c index d8434d4..3dcbd29 100644
> --- a/drivers/dma/xilinx/xilinx_vdma.c
> +++ b/drivers/dma/xilinx/xilinx_vdma.c
> @@ -98,7 +98,11 @@
> #define XILINX_VDMA_FRMDLY_STRIDE_FRMDLY_SHIFT 24
> #define XILINX_VDMA_FRMDLY_STRIDE_STRIDE_SHIFT 0
>
> +#if defined(CONFIG_PHYS_ADDR_T_64BIT)

Strictly speaking that should be CONFIG_ARCH_DMA_ADDR_T_64BIT.

> +#define XILINX_VDMA_REG_START_ADDRESS(n) (0x000c + 8 * (n))
> +#else
> #define XILINX_VDMA_REG_START_ADDRESS(n) (0x000c + 4 * (n))
> +#endif
>
> /* HW specific definitions */
> #define XILINX_VDMA_MAX_CHANS_PER_DEVICE 0x2
> @@ -143,16 +147,16 @@
> * @next_desc: Next Descriptor Pointer @0x00
> * @pad1: Reserved @0x04
> * @buf_addr: Buffer address @0x08
> - * @pad2: Reserved @0x0C
> - * @vsize: Vertical Size @0x10
> - * @hsize: Horizontal Size @0x14
> + * @pad2: Reserved @0x10
> + * @vsize: Vertical Size @0x14
> + * @hsize: Horizontal Size @0x18
> * @stride: Number of bytes between the first
> - * pixels of each horizontal line @0x18
> + * pixels of each horizontal line @0x1C
> */
> struct xilinx_vdma_desc_hw {
> u32 next_desc;
> u32 pad1;
> - u32 buf_addr;
> + u64 buf_addr;

This will change the descriptor layout for 32-bit VDMA, I don't think that's
right.

> u32 pad2;
> u32 vsize;
> u32 hsize;
> @@ -272,6 +276,20 @@ static inline void vdma_desc_write(struct
> xilinx_vdma_chan *chan, u32 reg, vdma_write(chan, chan->desc_offset + reg,
> value);
> }
>
> +#if defined(CONFIG_PHYS_ADDR_T_64BIT)
> +static inline void vdma_desc_write_64(struct xilinx_vdma_chan *chan, u32
> reg,
> + u64 value)
> +{
> + /* Write the lsb 32 bits*/
> + writel(lower_32_bits(value),
> + chan->xdev->regs + chan->desc_offset + reg);
> +
> + /* Write the msb 32 bits */
> + writel(upper_32_bits(value),
> + chan->xdev->regs + chan->desc_offset + reg + 4);

So the CPU can't perform 64-bit register access ?

How is 64 bit DMA addressing implemented ? Can you use a 64-bit VDMA on a 32-
bit platform with LPAE ? Can you use a 32-bit VDMA on a 64-bit platform ?
Given that VDMA is an IP core you can instantiate in the programmable logic I
expect some level of flexibility to be possible, but this patch doesn't seem
to support it. Please provide more context to allow a proper review (and
please include it in the commit message of v2).

> +}
> +#endif
> +
> static inline u32 vdma_ctrl_read(struct xilinx_vdma_chan *chan, u32 reg)
> {
> return vdma_read(chan, chan->ctrl_offset + reg);
> @@ -700,9 +718,15 @@ static void xilinx_vdma_start_transfer(struct
> xilinx_vdma_chan *chan) int i = 0;
>
> list_for_each_entry(segment, &desc->segments, node) {
> - vdma_desc_write(chan,
> +#if defined(CONFIG_PHYS_ADDR_T_64BIT)
> + vdma_desc_write_64(chan,
> XILINX_VDMA_REG_START_ADDRESS(i++),
> segment->hw.buf_addr);
> +#else
> + vdma_desc_write(chan,
> + XILINX_VDMA_REG_START_ADDRESS(i++),
> + (u32)segment->hw.buf_addr);
> +#endif
> last = segment;
> }

--
Regards,

Laurent Pinchart