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

[Bin Meng]

Hi Francisco,

On Thu, Dec 3, 2020 at 8:54 PM Francisco Iglesias
<frasse.iglesias@gmail.com> wrote:
>
> 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

Thanks for the review. All of your comments will be addressed in v2.

Regards,
Bin