Re: [Qemu-devel] [PATCH v2] xilinx_spips: Make dma transactions as per dma_burst_size

["Edgar E. Iglesias" <edgar.iglesias@xilinx.com>]

On Wed, Jun 20, 2018 at 02:00:00AM +0530, Sai Pavan Boddu wrote:
> Qspi dma has a burst length of 64 bytes, So limit transaction length to
> 64 max.
> 
> Signed-off-by: Sai Pavan Boddu <saipava@xilinx.com>
> ---
>  hw/ssi/xilinx_spips.c         | 20 +++++++++++++++++---
>  include/hw/ssi/xilinx_spips.h |  5 ++++-
>  2 files changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
> index 03f5fae..0ea57d1 100644
> --- a/hw/ssi/xilinx_spips.c
> +++ b/hw/ssi/xilinx_spips.c
> @@ -851,12 +851,17 @@ static void xlnx_zynqmp_qspips_notify(void *opaque)
>      {
>          size_t ret;
>          uint32_t num;
> -        const void *rxd = pop_buf(recv_fifo, 4, &num);
> +        const void *rxd;
> +        int len;
> +
> +        len = recv_fifo->num >= rq->dma_burst_size ? rq->dma_burst_size :
> +                                                   recv_fifo->num;
> +        rxd = pop_buf(recv_fifo, len, &num);
>  
>          memcpy(rq->dma_buf, rxd, num);
>  
> -        ret = stream_push(rq->dma, rq->dma_buf, 4);
> -        assert(ret == 4);
> +        ret = stream_push(rq->dma, rq->dma_buf, num);
> +        assert(ret == num);
>          xlnx_zynqmp_qspips_check_flush(rq);
>      }
>  }
> @@ -1337,6 +1342,9 @@ static void xlnx_zynqmp_qspips_realize(DeviceState *dev, Error **errp)
>      fifo8_create(&s->rx_fifo_g, xsc->rx_fifo_size);
>      fifo8_create(&s->tx_fifo_g, xsc->tx_fifo_size);
>      fifo32_create(&s->fifo_g, 32);
> +    if (s->dma_burst_size > QSPI_DMA_MAX_BURST_SIZE) {
> +        s->dma_burst_size = QSPI_DMA_MAX_BURST_SIZE;
> +    }


I think it's better to let the user know that the chosen value was out of
range, look at how num-busses is handled at the begining of this function.




>  }
>  
>  static void xlnx_zynqmp_qspips_init(Object *obj)
> @@ -1411,6 +1419,11 @@ static const VMStateDescription vmstate_xlnx_zynqmp_qspips = {
>      }
>  };
>  
> +static Property xilinx_zynqmp_qspips_properties[] = {
> +    DEFINE_PROP_UINT32("dma-burst-size", XlnxZynqMPQSPIPS, dma_burst_size, 64),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
>  static Property xilinx_qspips_properties[] = {
>      /* We had to turn this off for 2.10 as it is not compatible with migration.
>       * It can be enabled but will prevent the device to be migrated.
> @@ -1463,6 +1476,7 @@ static void xlnx_zynqmp_qspips_class_init(ObjectClass *klass, void * data)
>      dc->realize = xlnx_zynqmp_qspips_realize;
>      dc->reset = xlnx_zynqmp_qspips_reset;
>      dc->vmsd = &vmstate_xlnx_zynqmp_qspips;
> +    dc->props = xilinx_zynqmp_qspips_properties;
>      xsc->reg_ops = &xlnx_zynqmp_qspips_ops;
>      xsc->rx_fifo_size = RXFF_A_Q;
>      xsc->tx_fifo_size = TXFF_A_Q;
> diff --git a/include/hw/ssi/xilinx_spips.h b/include/hw/ssi/xilinx_spips.h
> index d398a4e..bc5596a 100644
> --- a/include/hw/ssi/xilinx_spips.h
> +++ b/include/hw/ssi/xilinx_spips.h
> @@ -37,6 +37,8 @@ typedef struct XilinxSPIPS XilinxSPIPS;
>  /* Bite off 4k chunks at a time */
>  #define LQSPI_CACHE_SIZE 1024
>  
> +#define QSPI_DMA_MAX_BURST_SIZE 2048
> +
>  typedef enum {
>      READ = 0x3,         READ_4 = 0x13,
>      FAST_READ = 0xb,    FAST_READ_4 = 0x0c,
> @@ -95,7 +97,8 @@ typedef struct {
>      XilinxQSPIPS parent_obj;
>  
>      StreamSlave *dma;
> -    uint8_t dma_buf[4];
> +    uint8_t dma_buf[QSPI_DMA_MAX_BURST_SIZE];
> +    uint32_t dma_burst_size;
>      int gqspi_irqline;
>  
>      uint32_t regs[XLNX_ZYNQMP_SPIPS_R_MAX];
> -- 
> 2.7.4
>