Re: [PATCH 3/3] dmaengine: xilinx_dma: Fix 64-bit simple CDMA transfer

[Vinod]

On 28-08-18, 14:03, Radhey Shyam Pandey wrote:
> > On 27-07-18, 16:20, Radhey Shyam Pandey wrote:
> > > In AXI CDMA simple mode also pass MSB bits of source and destination
> > > address to xilinx_write function. This fixes simple CDMA operation
> > > mode using 64-bit addressing.
> > >
> > > Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@xxxxxxxxxx>
> > > Signed-off-by: Michal Simek <michal.simek@xxxxxxxxxx>
> > > ---
> > >  drivers/dma/xilinx/xilinx_dma.c |    6 ++++--
> > >  1 files changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> > > index a37871e..2e15d86 100644
> > > --- a/drivers/dma/xilinx/xilinx_dma.c
> > > +++ b/drivers/dma/xilinx/xilinx_dma.c
> > > @@ -1245,8 +1245,10 @@ static void xilinx_cdma_start_transfer(struct
> > xilinx_dma_chan *chan)
> > >
> > >  		hw = &segment->hw;
> > >
> > > -		xilinx_write(chan, XILINX_CDMA_REG_SRCADDR, hw-
> > >src_addr);
> > > -		xilinx_write(chan, XILINX_CDMA_REG_DSTADDR, hw-
> > >dest_addr);
> > > +		xilinx_write(chan, XILINX_CDMA_REG_SRCADDR,
> > (dma_addr_t)
> > > +			     ((u64)hw->src_addr_msb << 32 | hw->src_addr));
> > 
> > so this is:
> >         (dma_addr_t)((u64)hw->src_addr_msb << 32 | hw->src_addr)
> > 
> > what is src_addr data type? I think its u32. It would be better to
> > update xilinx_write() to take u64 and not dma_addr_t.
> 
> Yes, src_addr_msb and src_addr BD fields are u32. To explain: There is no
> prob in xilinx_write it takes dma_addr_t as an arg which is 32/64 bit 
> depending on _DMA_ADDR_T_64BIT. In 64bit CDMA transfer, there was a bug
> i.e in the call to xilinx_write src_addr_msb 32 bits were not passed. To fix
> that combine MSB and LSB 32 bits before passing it to xilinx_write.

Yeah that part was clear but the implementation can be better..

-- 
~Vinod