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SubjectRe: [PATCH v5 4/7] dmaengine: xilinx_dma: program hardware supported buffer length
On Tue, Sep 18, 2018 at 6:25 PM Vinod <vkoul@kernel.org> wrote:
>
> On 07-09-18, 08:24, Andrea Merello wrote:
> > From: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
> >
> > AXI-DMA IP supports configurable (c_sg_length_width) buffer length
> > register width, hence read buffer length (xlnx,sg-length-width) DT
> > property and ensure that driver doesn't program buffer length
> > exceeding the supported limit. For VDMA and CDMA there is no change.
> >
> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: devicetree@vger.kernel.org
> > Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xilinx.com>
> > Signed-off-by: Michal Simek <michal.simek@xilinx.com>
> > Signed-off-by: Andrea Merello <andrea.merello@gmail.com> [rebase, reword]
> > ---
> > Changes in v2:
> > - drop original patch and replace with the one in Xilinx tree
> > Changes in v3:
> > - cc DT maintainers/ML
> > Changes in v4:
> > - upper bound for the property should be 26, not 23
> > - add warn for width > 23 as per xilinx original patch
> > - rework due to changes introduced in 1/6
> > Changes in v5:
> > None
> > ---
> > drivers/dma/xilinx/xilinx_dma.c | 36 +++++++++++++++++++++++++--------
> > 1 file changed, 28 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> > index aaa6de8a70e4..b17f24e4ec35 100644
> > --- a/drivers/dma/xilinx/xilinx_dma.c
> > +++ b/drivers/dma/xilinx/xilinx_dma.c
> > @@ -158,7 +158,9 @@
> > #define XILINX_DMA_REG_BTT 0x28
> >
> > /* AXI DMA Specific Masks/Bit fields */
> > -#define XILINX_DMA_MAX_TRANS_LEN GENMASK(22, 0)
> > +#define XILINX_DMA_MAX_TRANS_LEN_MIN 8
> > +#define XILINX_DMA_MAX_TRANS_LEN_MAX 23
> > +#define XILINX_DMA_V2_MAX_TRANS_LEN_MAX 26
> > #define XILINX_DMA_CR_COALESCE_MAX GENMASK(23, 16)
> > #define XILINX_DMA_CR_CYCLIC_BD_EN_MASK BIT(4)
> > #define XILINX_DMA_CR_COALESCE_SHIFT 16
> > @@ -418,6 +420,7 @@ struct xilinx_dma_config {
> > * @rxs_clk: DMA s2mm stream clock
> > * @nr_channels: Number of channels DMA device supports
> > * @chan_id: DMA channel identifier
> > + * @max_buffer_len: Max buffer length
> > */
> > struct xilinx_dma_device {
> > void __iomem *regs;
> > @@ -437,6 +440,7 @@ struct xilinx_dma_device {
> > struct clk *rxs_clk;
> > u32 nr_channels;
> > u32 chan_id;
> > + u32 max_buffer_len;
> > };
> >
> > /* Macros */
> > @@ -964,7 +968,7 @@ static int xilinx_dma_calc_copysize(struct xilinx_dma_chan *chan,
> > int size, int done)
> > {
> > size_t copy = min_t(size_t, size - done,
> > - XILINX_DMA_MAX_TRANS_LEN);
> > + chan->xdev->max_buffer_len);
>
> hmm why not add max_buffer_len in patch 1 again, and then use default
> len as XILINX_DMA_MAX_TRANS_LEN and add multiple lengths here :)

Sorry, I'm not getting your point. Could you please elaborate the "add
multiple lengths here" thing ?

> -
> ~Vinod

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