Re: [PATCH v3 5/5] dmaengine: xilinx: xdma: Ease dma_pool alignment requirements

[Lizhi Hou]

On 11/27/23 08:43, Lizhi Hou wrote:
> On 11/24/23 11:25, Jan Kuliga wrote:
> > According to the XDMA datasheet (PG195), the address of any descriptor
> > must be 32 byte aligned. The datasheet also states that a contiguous
> > block of descriptors must not cross a 4k address boundary. Therefore,
> > it is possible to ease the pressure put on the dma_pool allocator
> > just by requiring sufficient alignment and boundary values. Add proper
> > macro definition and change the values passed into the
> > dma_pool_create().
> >
> > Signed-off-by: Jan Kuliga <jankul@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/dma/xilinx/xdma-regs.h | 7 ++++---
> >   drivers/dma/xilinx/xdma.c      | 6 +++---
> >   2 files changed, 7 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/dma/xilinx/xdma-regs.h 
> > b/drivers/dma/xilinx/xdma-regs.h
> > index 6bf7ae84e452..d5cb12e6b8d4 100644
> > --- a/drivers/dma/xilinx/xdma-regs.h
> > +++ b/drivers/dma/xilinx/xdma-regs.h
> > @@ -64,9 +64,10 @@ struct xdma_hw_desc {
> >       __le64        next_desc;
> >   };
> >   -#define XDMA_DESC_SIZE        sizeof(struct xdma_hw_desc)
> > -#define XDMA_DESC_BLOCK_SIZE    (XDMA_DESC_SIZE * XDMA_DESC_ADJACENT)
> > -#define XDMA_DESC_BLOCK_ALIGN    4096
> > +#define XDMA_DESC_SIZE            sizeof(struct xdma_hw_desc)
> > +#define XDMA_DESC_BLOCK_SIZE        (XDMA_DESC_SIZE * 
> > XDMA_DESC_ADJACENT)
> > +#define XDMA_DESC_BLOCK_ALIGN        32
> > +#define XDMA_DESC_BLOCK_BOUNDARY    4096
> >     /*
> >    * Channel registers
> > diff --git a/drivers/dma/xilinx/xdma.c b/drivers/dma/xilinx/xdma.c
> > index de4615bd4ee5..d32ae93e18b6 100644
> > --- a/drivers/dma/xilinx/xdma.c
> > +++ b/drivers/dma/xilinx/xdma.c
> > @@ -735,9 +735,9 @@ static int xdma_alloc_chan_resources(struct 
> > dma_chan *chan)
> >           return -EINVAL;
> >       }
> >   -    xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan),
> > -                           dev, XDMA_DESC_BLOCK_SIZE,
> > -                           XDMA_DESC_BLOCK_ALIGN, 0);
> > +    xdma_chan->desc_pool = dma_pool_create(dma_chan_name(chan), dev,
> > +                XDMA_DESC_BLOCK_SIZE, XDMA_DESC_BLOCK_ALIGN,
> > +                        XDMA_DESC_BLOCK_BOUNDARY);
> >       if (!xdma_chan->desc_pool) {
> >           xdma_err(xdev, "unable to allocate descriptor pool");
> >           return -ENOMEM;
>
> This is probably not needed. The 32 adjacent descriptors here is 1024 
> bytes. Defining 4k alignment should be good enough.
Oh, Just noticed the you have changed the alignment to 32. Sorry, I just 
hit send too quick.
> Thanks,
>
> Lizhi