[v1,5/5] dma/xlnx-zdma: Reorg to fix CUR_DSCR

From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>

Reorganize the descriptor handling so that CUR_DSCR always
points to the next descriptor to be processed.

Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
---
 hw/dma/xlnx-zdma.c | 47 ++++++++++++++++++++++------------------------
 1 file changed, 22 insertions(+), 25 deletions(-)

On Thu, Apr 2, 2020 at 6:50 AM Edgar E. Iglesias
<edgar.iglesias@gmail.com> wrote:
>
> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>
> Reorganize the descriptor handling so that CUR_DSCR always
> points to the next descriptor to be processed.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  hw/dma/xlnx-zdma.c | 47 ++++++++++++++++++++++------------------------
>  1 file changed, 22 insertions(+), 25 deletions(-)
>
> diff --git a/hw/dma/xlnx-zdma.c b/hw/dma/xlnx-zdma.c
> index e856d233f2..1c45367f3c 100644
> --- a/hw/dma/xlnx-zdma.c
> +++ b/hw/dma/xlnx-zdma.c
> @@ -333,10 +333,28 @@ static void zdma_load_src_descriptor(XlnxZDMA *s)
>      }
>  }
>
> +static void zdma_update_descr_addr(XlnxZDMA *s, bool type,
> +                                   unsigned int basereg)
> +{
> +    uint64_t addr, next;
> +
> +    if (type == DTYPE_LINEAR) {
> +        addr = zdma_get_regaddr64(s, basereg);
> +        next = addr + sizeof(s->dsc_dst);
> +    } else {
> +        addr = zdma_get_regaddr64(s, basereg);
> +        addr += sizeof(s->dsc_dst);
> +        address_space_read(s->dma_as, addr, s->attr, (void *) &next, 8);
> +    }
> +
> +    zdma_put_regaddr64(s, basereg, next);
> +}
> +
>  static void zdma_load_dst_descriptor(XlnxZDMA *s)
>  {
>      uint64_t dst_addr;
>      unsigned int ptype = ARRAY_FIELD_EX32(s->regs, ZDMA_CH_CTRL0, POINT_TYPE);
> +    bool dst_type;
>
>      if (ptype == PT_REG) {
>          memcpy(&s->dsc_dst, &s->regs[R_ZDMA_CH_DST_DSCR_WORD0],
> @@ -349,24 +367,10 @@ static void zdma_load_dst_descriptor(XlnxZDMA *s)
>      if (!zdma_load_descriptor(s, dst_addr, &s->dsc_dst)) {
>          ARRAY_FIELD_DP32(s->regs, ZDMA_CH_ISR, AXI_RD_DST_DSCR, true);
>      }
> -}
> -
> -static uint64_t zdma_update_descr_addr(XlnxZDMA *s, bool type,
> -                                       unsigned int basereg)
> -{
> -    uint64_t addr, next;
>
> -    if (type == DTYPE_LINEAR) {
> -        next = zdma_get_regaddr64(s, basereg);
> -        next += sizeof(s->dsc_dst);
> -        zdma_put_regaddr64(s, basereg, next);
> -    } else {
> -        addr = zdma_get_regaddr64(s, basereg);
> -        addr += sizeof(s->dsc_dst);
> -        address_space_read(s->dma_as, addr, s->attr, &next, 8);
> -        zdma_put_regaddr64(s, basereg, next);
> -    }
> -    return next;
> +    /* Advance the descriptor pointer.  */
> +    dst_type = FIELD_EX32(s->dsc_dst.words[3], ZDMA_CH_DST_DSCR_WORD3, TYPE);
> +    zdma_update_descr_addr(s, dst_type, R_ZDMA_CH_DST_CUR_DSCR_LSB);
>  }
>
>  static void zdma_write_dst(XlnxZDMA *s, uint8_t *buf, uint32_t len)
> @@ -387,14 +391,7 @@ static void zdma_write_dst(XlnxZDMA *s, uint8_t *buf, uint32_t len)
>          dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
>                                SIZE);
>          if (dst_size == 0 && ptype == PT_MEM) {
> -            uint64_t next;
> -            bool dst_type = FIELD_EX32(s->dsc_dst.words[3],
> -                                       ZDMA_CH_DST_DSCR_WORD3,
> -                                       TYPE);
> -
> -            next = zdma_update_descr_addr(s, dst_type,
> -                                          R_ZDMA_CH_DST_CUR_DSCR_LSB);
> -            zdma_load_descriptor(s, next, &s->dsc_dst);
> +            zdma_load_dst_descriptor(s);
>              dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
>                                    SIZE);
>          }
> --
> 2.20.1
>
>

On [2020 Apr 02] Thu 15:47:21, Edgar E. Iglesias wrote:
> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
> 
> Reorganize the descriptor handling so that CUR_DSCR always
> points to the next descriptor to be processed.
> 
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

Reviewed-by: Francisco Iglesias <frasse.iglesias@gmail.com>

> ---
>  hw/dma/xlnx-zdma.c | 47 ++++++++++++++++++++++------------------------
>  1 file changed, 22 insertions(+), 25 deletions(-)
> 
> diff --git a/hw/dma/xlnx-zdma.c b/hw/dma/xlnx-zdma.c
> index e856d233f2..1c45367f3c 100644
> --- a/hw/dma/xlnx-zdma.c
> +++ b/hw/dma/xlnx-zdma.c
> @@ -333,10 +333,28 @@ static void zdma_load_src_descriptor(XlnxZDMA *s)
>      }
>  }
>  
> +static void zdma_update_descr_addr(XlnxZDMA *s, bool type,
> +                                   unsigned int basereg)
> +{
> +    uint64_t addr, next;
> +
> +    if (type == DTYPE_LINEAR) {
> +        addr = zdma_get_regaddr64(s, basereg);
> +        next = addr + sizeof(s->dsc_dst);
> +    } else {
> +        addr = zdma_get_regaddr64(s, basereg);
> +        addr += sizeof(s->dsc_dst);
> +        address_space_read(s->dma_as, addr, s->attr, (void *) &next, 8);
> +    }
> +
> +    zdma_put_regaddr64(s, basereg, next);
> +}
> +
>  static void zdma_load_dst_descriptor(XlnxZDMA *s)
>  {
>      uint64_t dst_addr;
>      unsigned int ptype = ARRAY_FIELD_EX32(s->regs, ZDMA_CH_CTRL0, POINT_TYPE);
> +    bool dst_type;
>  
>      if (ptype == PT_REG) {
>          memcpy(&s->dsc_dst, &s->regs[R_ZDMA_CH_DST_DSCR_WORD0],
> @@ -349,24 +367,10 @@ static void zdma_load_dst_descriptor(XlnxZDMA *s)
>      if (!zdma_load_descriptor(s, dst_addr, &s->dsc_dst)) {
>          ARRAY_FIELD_DP32(s->regs, ZDMA_CH_ISR, AXI_RD_DST_DSCR, true);
>      }
> -}
> -
> -static uint64_t zdma_update_descr_addr(XlnxZDMA *s, bool type,
> -                                       unsigned int basereg)
> -{
> -    uint64_t addr, next;
>  
> -    if (type == DTYPE_LINEAR) {
> -        next = zdma_get_regaddr64(s, basereg);
> -        next += sizeof(s->dsc_dst);
> -        zdma_put_regaddr64(s, basereg, next);
> -    } else {
> -        addr = zdma_get_regaddr64(s, basereg);
> -        addr += sizeof(s->dsc_dst);
> -        address_space_read(s->dma_as, addr, s->attr, &next, 8);
> -        zdma_put_regaddr64(s, basereg, next);
> -    }
> -    return next;
> +    /* Advance the descriptor pointer.  */
> +    dst_type = FIELD_EX32(s->dsc_dst.words[3], ZDMA_CH_DST_DSCR_WORD3, TYPE);
> +    zdma_update_descr_addr(s, dst_type, R_ZDMA_CH_DST_CUR_DSCR_LSB);
>  }
>  
>  static void zdma_write_dst(XlnxZDMA *s, uint8_t *buf, uint32_t len)
> @@ -387,14 +391,7 @@ static void zdma_write_dst(XlnxZDMA *s, uint8_t *buf, uint32_t len)
>          dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
>                                SIZE);
>          if (dst_size == 0 && ptype == PT_MEM) {
> -            uint64_t next;
> -            bool dst_type = FIELD_EX32(s->dsc_dst.words[3],
> -                                       ZDMA_CH_DST_DSCR_WORD3,
> -                                       TYPE);
> -
> -            next = zdma_update_descr_addr(s, dst_type,
> -                                          R_ZDMA_CH_DST_CUR_DSCR_LSB);
> -            zdma_load_descriptor(s, next, &s->dsc_dst);
> +            zdma_load_dst_descriptor(s);
>              dst_size = FIELD_EX32(s->dsc_dst.words[2], ZDMA_CH_DST_DSCR_WORD2,
>                                    SIZE);
>          }
> -- 
> 2.20.1
>

On Thu, 2 Apr 2020 at 14:46, Edgar E. Iglesias <edgar.iglesias@gmail.com> wrote:
>
> From: "Edgar E. Iglesias" <edgar.iglesias@xilinx.com>
>
> Reorganize the descriptor handling so that CUR_DSCR always
> points to the next descriptor to be processed.
>
> Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
> ---

This is just moved-code in this patch so I think it's
a separate issue, but it looks like you have an endianness
bug here:

> +static void zdma_update_descr_addr(XlnxZDMA *s, bool type,
> +                                   unsigned int basereg)
> +{
> +    uint64_t addr, next;
> +
> +    if (type == DTYPE_LINEAR) {
> +        addr = zdma_get_regaddr64(s, basereg);
> +        next = addr + sizeof(s->dsc_dst);
> +    } else {
> +        addr = zdma_get_regaddr64(s, basereg);
> +        addr += sizeof(s->dsc_dst);
> +        address_space_read(s->dma_as, addr, s->attr, (void *) &next, 8);

This reads 8 bytes into the uint64_t 'next', which means
that the value from C's point of view will be different
for big-endian and little-endian hosts. You probably wanted
address_space_ldq_le(), assuming the h/w always does
little-endian reads and that these get_regaddr64 and
put_regaddr64 functions work with host-endian integers.

There's a similar problem elsewhere in the device where
it does this:
    address_space_read(s->dma_as, addr, s->attr, buf, sizeof(XlnxZDMADescr));
and assumes the guest structure is the same layout and
endianness as the host struct XlnxDMADescr.

I'm not a huge fan of defining host C structs to match
guest data structures, but if you want to go that way
you ought to (a) be byteswapping the contents appropriately
and (b) have a compile-time assert that the size of the
struct is what you think it is and the compiler hasn't
inserted any helpful extra padding.

thanks
-- PMM