Re: [PATCH v2 18/42] esp: accumulate SCSI commands for PDMA transfers in cmdbuf instead of pdma_buf

[Laurent Vivier]

Le 09/02/2021 à 20:29, Mark Cave-Ayland a écrit :
> ESP SCSI commands are already accumulated in cmdbuf and so there is no need to
> keep a separate pdma_buf buffer. Accumulate SCSI commands for PDMA transfers 
> in
> cmdbuf instead of pdma_buf so update cmdlen accordingly and change pdma_origin
> for PDMA transfers to CMD which allows the PDMA origin to be removed.
> 
> This commit also removes a stray memcpy() from get_cmd() which is a no-op 
> because
> cmdlen is always zero at the start of a command.
> 
> Notionally the removal of pdma_buf from vmstate_esp_pdma also breaks migration
> compatibility for the PDMA subsection until its complete removal by the end of
> the series.
> 
> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>  hw/scsi/esp.c         | 56 +++++++++++++++++++------------------------
>  include/hw/scsi/esp.h |  2 --
>  2 files changed, 25 insertions(+), 33 deletions(-)
> 
> diff --git a/hw/scsi/esp.c b/hw/scsi/esp.c
> index 7134c0aff4..b846f022fb 100644
> --- a/hw/scsi/esp.c
> +++ b/hw/scsi/esp.c
> @@ -139,8 +139,6 @@ static void set_pdma(ESPState *s, enum pdma_origin_id 
> origin,
>  static uint8_t *get_pdma_buf(ESPState *s)
>  {
>      switch (s->pdma_origin) {
> -    case PDMA:
> -        return s->pdma_buf;
>      case TI:
>          return s->ti_buf;
>      case CMD:
> @@ -161,14 +159,12 @@ static uint8_t esp_pdma_read(ESPState *s)
>      }
>  
>      switch (s->pdma_origin) {
> -    case PDMA:
> -        val = s->pdma_buf[s->pdma_cur++];
> -        break;
>      case TI:
>          val = s->ti_buf[s->pdma_cur++];
>          break;
>      case CMD:
> -        val = s->cmdbuf[s->pdma_cur++];
> +        val = s->cmdbuf[s->cmdlen++];
> +        s->pdma_cur++;
>          break;
>      case ASYNC:
>          val = s->async_buf[s->pdma_cur++];
> @@ -193,14 +189,12 @@ static void esp_pdma_write(ESPState *s, uint8_t val)
>      }
>  
>      switch (s->pdma_origin) {
> -    case PDMA:
> -        s->pdma_buf[s->pdma_cur++] = val;
> -        break;
>      case TI:
>          s->ti_buf[s->pdma_cur++] = val;
>          break;
>      case CMD:
> -        s->cmdbuf[s->pdma_cur++] = val;
> +        s->cmdbuf[s->cmdlen++] = val;
> +        s->pdma_cur++;
>          break;
>      case ASYNC:
>          s->async_buf[s->pdma_cur++] = val;
> @@ -256,8 +250,7 @@ static uint32_t get_cmd(ESPState *s, uint8_t *buf, 
> uint8_t buflen)
>          if (s->dma_memory_read) {
>              s->dma_memory_read(s->dma_opaque, buf, dmalen);
>          } else {
> -            memcpy(s->pdma_buf, buf, dmalen);
> -            set_pdma(s, PDMA, 0, dmalen);
> +            set_pdma(s, CMD, 0, dmalen);
>              esp_raise_drq(s);
>              return 0;
>          }
> @@ -316,24 +309,24 @@ static void satn_pdma_cb(ESPState *s)
>      if (get_cmd_cb(s) < 0) {
>          return;
>      }
> -    if (s->pdma_cur != s->pdma_start) {
> -        do_cmd(s, get_pdma_buf(s) + s->pdma_start);
> +    s->do_cmd = 0;
> +    if (s->cmdlen) {
> +        do_cmd(s, s->cmdbuf);

I don't understant how you can remove the pdma_start: normally it is here to 
keep track of the
position in the pDMA if the migration is occuraing while a pDMA transfer.

Thanks,
Laurent