Re: [PATCH] hw/block: m25p80: Implement AAI-WP command support for SST flashes

[Francisco Iglesias]

Hello Bin,

On [2020 Dec 02] Wed 22:30:37, Bin Meng wrote:
> From: Xuzhou Cheng <xuzhou.cheng@windriver.com>
> 
> Auto Address Increment (AAI) Word-Program is a special command of
> SST flashes. AAI-WP allows multiple bytes of data to be programmed
> without re-issuing the next sequential address location.
> 
> Signed-off-by: Xuzhou Cheng <xuzhou.cheng@windriver.com>
> Signed-off-by: Bin Meng <bin.meng@windriver.com>
> ---
> 
>  hw/block/m25p80.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/hw/block/m25p80.c b/hw/block/m25p80.c
> index 9b36762df9..f225d9c96d 100644
> --- a/hw/block/m25p80.c
> +++ b/hw/block/m25p80.c
> @@ -359,6 +359,7 @@ typedef enum {
>      QPP_4 = 0x34,
>      RDID_90 = 0x90,
>      RDID_AB = 0xab,
> +    AAI_WP = 0xad,
>  
>      ERASE_4K = 0x20,
>      ERASE4_4K = 0x21,
> @@ -449,6 +450,7 @@ struct Flash {
>      bool four_bytes_address_mode;
>      bool reset_enable;
>      bool quad_enable;
> +    bool aai_enable;

We need to add above addition also into the vmstate.

>      uint8_t ear;
>  
>      int64_t dirty_page;
> @@ -661,6 +663,7 @@ static void complete_collecting_data(Flash *s)
>      case PP:
>      case PP4:
>      case PP4_4:
> +    case AAI_WP:
>          s->state = STATE_PAGE_PROGRAM;
>          break;
>      case READ:
> @@ -1010,6 +1013,9 @@ static void decode_new_cmd(Flash *s, uint32_t value)

Since only 3 cmds are allowed while within AAI programming sequence [1] I think
a warning migt be good have before the command switch case, similar to:

if (get_man(s) == MAN_SST && s->aai_enable && !is_valid_aai_cmd(value)) {
    qemu_log_mask(LOG_GUEST_ERROR,
                  "M25P80: Invalid cmd within AAI programming sequence");
}

>  
>      case WRDI:
>          s->write_enable = false;
> +        if (get_man(s) == MAN_SST) {
> +            s->aai_enable = false;
> +        }
>          break;
>      case WREN:
>          s->write_enable = true;
> @@ -1162,6 +1168,17 @@ static void decode_new_cmd(Flash *s, uint32_t value)
>      case RSTQIO:
>          s->quad_enable = false;
>          break;
> +    case AAI_WP:
> +        if (get_man(s) == MAN_SST && s->write_enable) {
> +            if (s->aai_enable) {
> +                s->state = STATE_PAGE_PROGRAM;
> +            } else {
> +                s->aai_enable = true;
> +                s->needed_bytes = get_addr_length(s);
> +                s->state = STATE_COLLECTING_DATA;
> +            }

Perhaps a qemu_log_mask in an 'else' could be useful here also:

} else {
    qemu_log_mask(LOG_GUEST_ERROR, "M25P80: %s"
                  (get_man(s) == MAN_SST) ? "AAI_WP with write protect" :
                                            "Unknown CMD: 0xAD\n");

Lastly, [1] also says that the address shouldn't wrapp around when in AAI mode,
so we need a check before doing that also I think. 

Best regards,
Francisco Iglesias

[1] http://ww1.microchip.com/downloads/en/devicedoc/s71271_04.pdf

> +        }
> +        break;
>      default:
>          s->pos = 0;
>          s->len = 1;
> -- 
> 2.25.1
> 
>