Re: [QEMU][PATCH v4] ssi: xilinx_spips: Skip spi bus update for a few register writes

[Francisco Iglesias]

On [2019 Oct 21] Mon 20:11:51, Sai Pavan Boddu wrote:
Hi Sai,

> A few of the register writes need not update the spi bus state, so just

s/of the/configuration/

> return after reg write. Added few more dummy register offsets which need

s/reg/register/

> the same behaviour.

I apologize but I forgot to mention that below are not dummy registers
(they are configuration registers). Would it be ok for you to remove the
last (second) sentence above? 

The patch looks ok to me after that! (Also tested it!)

Best regards,
Francisco Iglesias

> 
> Signed-off-by: Sai Pavan Boddu <address@hidden>
> ---
> Changes for V2:
>       Just skip update of spips cs and fifos
>       Update commit message accordingly
> Changes for V3:
>       Avoid checking for zynqmp qspi
>       Skip spi bus update for few of the registers
> Changes for V4:
>       Move the register list to existing switch case above.
> 
>  hw/ssi/xilinx_spips.c | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ssi/xilinx_spips.c b/hw/ssi/xilinx_spips.c
> index a309c71..0d6c2e1 100644
> --- a/hw/ssi/xilinx_spips.c
> +++ b/hw/ssi/xilinx_spips.c
> @@ -109,6 +109,7 @@
>  #define R_GPIO              (0x30 / 4)
>  #define R_LPBK_DLY_ADJ      (0x38 / 4)
>  #define R_LPBK_DLY_ADJ_RESET (0x33)
> +#define R_IOU_TAPDLY_BYPASS (0x3C / 4)
>  #define R_TXD1              (0x80 / 4)
>  #define R_TXD2              (0x84 / 4)
>  #define R_TXD3              (0x88 / 4)
> @@ -139,6 +140,8 @@
>  #define R_LQSPI_STS         (0xA4 / 4)
>  #define LQSPI_STS_WR_RECVD      (1 << 1)
>  
> +#define R_DUMMY_CYCLE_EN    (0xC8 / 4)
> +#define R_ECO               (0xF8 / 4)
>  #define R_MOD_ID            (0xFC / 4)
>  
>  #define R_GQSPI_SELECT          (0x144 / 4)
> @@ -970,6 +973,7 @@ static void xilinx_spips_write(void *opaque, hwaddr addr,
>  {
>      int mask = ~0;
>      XilinxSPIPS *s = opaque;
> +    bool try_flush = true;
>  
>      DB_PRINT_L(0, "addr=" TARGET_FMT_plx " = %x\n", addr, (unsigned)value);
>      addr >>= 2;
> @@ -1019,13 +1023,23 @@ static void xilinx_spips_write(void *opaque, hwaddr 
> addr,
>          tx_data_bytes(&s->tx_fifo, (uint32_t)value, 3,
>                        s->regs[R_CONFIG] & R_CONFIG_ENDIAN);
>          goto no_reg_update;
> +    /* Skip SPI bus update for below registers writes */
> +    case R_GPIO:
> +    case R_LPBK_DLY_ADJ:
> +    case R_IOU_TAPDLY_BYPASS:
> +    case R_DUMMY_CYCLE_EN:
> +    case R_ECO:
> +        try_flush = false;
> +        break;
>      }
>      s->regs[addr] = (s->regs[addr] & ~mask) | (value & mask);
>  no_reg_update:
> -    xilinx_spips_update_cs_lines(s);
> -    xilinx_spips_check_flush(s);
> -    xilinx_spips_update_cs_lines(s);
> -    xilinx_spips_update_ixr(s);
> +    if (try_flush) {
> +        xilinx_spips_update_cs_lines(s);
> +        xilinx_spips_check_flush(s);
> +        xilinx_spips_update_cs_lines(s);
> +        xilinx_spips_update_ixr(s);
> +    }
>  }
>  
>  static const MemoryRegionOps spips_ops = {
> -- 
> 2.7.4
>