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SubjectRe: [PATCH v5] dma: Add Xilinx AXI Direct Memory Access Engine driver support
Hello!

I looked through your driver and have some comments.

On Mon, Mar 02, 2015 at 11:25:11PM +0530, Kedareswara rao Appana wrote:
> This is the driver for the AXI Direct Memory Access (AXI DMA)
> core, which is a soft Xilinx IP core that provides high-
> bandwidth direct memory access between memory and AXI4-Stream
> type target peripherals.
>
> Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
> Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
[..]
> +++ b/drivers/dma/Kconfig
> @@ -425,6 +425,19 @@ config IMG_MDC_DMA
> help
> Enable support for the IMG multi-threaded DMA controller (MDC).
>
> +config XILINX_DMA
> + tristate "Xilinx AXI DMA Engine"
> + depends on (ARCH_ZYNQ || MICROBLAZE)

Why do you need this dependency? I'm assuming this IP has usefulness
outside of microblaze and Zynq.

> + select DMA_ENGINE
> + help
> + Enable support for Xilinx AXI DMA Soft IP.
> +
> + This engine provides high-bandwidth direct memory access
> + between memory and AXI4-Stream type target peripherals.
> + It has two stream interfaces/channels, Memory Mapped to
> + Stream (MM2S) and Stream to Memory Mapped (S2MM) for the
> + data transfers.

Odd indention here. At least indent this paragraph like the sentence
above.

[..]
> +++ b/drivers/dma/xilinx/xilinx_dma.c
[..]
> +/**
> + * xilinx_dma_halt - Halt DMA channel
> + * @chan: Driver specific DMA channel
> + */
> +static void xilinx_dma_halt(struct xilinx_dma_chan *chan)
> +{
> + int loop = XILINX_DMA_LOOP_COUNT;
> +
> + dma_ctrl_clr(chan, XILINX_DMA_REG_CONTROL,
> + XILINX_DMA_CR_RUNSTOP_MASK);
> +
> + /* Wait for the hardware to halt */
> + do {
> + if (dma_ctrl_read(chan, XILINX_DMA_REG_STATUS) &
> + XILINX_DMA_SR_HALTED_MASK)
> + break;
> + } while (loop--);
> +
> + if (!loop) {

Looks like a very subtle off-by-one error here. (And elsewhere you use
this pattern).

Josh


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