Re: [PATCH] hw/nvram: Add at24c-eeprom support for small eeproms

[Patrick Venture <venture@google.com>]

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On Mon, Mar 14, 2022 at 2:12 PM Patrick Venture <venture@google.com> wrote:

> Tested: Verified at24c02 driver happy and contents matched
> expectations.
>
> Signed-off-by: Patrick Venture <venture@google.com>
> Reviewed-by: Hao Wu <wuhaotsh@google.com>
> ---
>  hw/nvram/eeprom_at24c.c | 52 +++++++++++++++++++++++++++--------------
>  1 file changed, 35 insertions(+), 17 deletions(-)
>
> diff --git a/hw/nvram/eeprom_at24c.c b/hw/nvram/eeprom_at24c.c
> index 01a3093600..abf9898f94 100644
> --- a/hw/nvram/eeprom_at24c.c
> +++ b/hw/nvram/eeprom_at24c.c
> @@ -45,6 +45,8 @@ struct EEPROMState {
>      bool changed;
>      /* during WRITE, # of address bytes transfered */
>      uint8_t haveaddr;
> +    /* whether it's 8-bit addressed or 16-bit */
> +    bool eightbit;
>
>      uint8_t *mem;
>
> @@ -85,7 +87,7 @@ uint8_t at24c_eeprom_recv(I2CSlave *s)
>      EEPROMState *ee = AT24C_EE(s);
>      uint8_t ret;
>
> -    if (ee->haveaddr == 1) {
> +    if (ee->haveaddr == 1 && !ee->eightbit) {
>          return 0xff;
>      }
>
> @@ -102,26 +104,35 @@ int at24c_eeprom_send(I2CSlave *s, uint8_t data)
>  {
>      EEPROMState *ee = AT24C_EE(s);
>
> -    if (ee->haveaddr < 2) {
> -        ee->cur <<= 8;
> -        ee->cur |= data;
> +    if (ee->haveaddr < 1) {
> +        ee->cur = data;
>          ee->haveaddr++;
> -        if (ee->haveaddr == 2) {
> -            ee->cur %= ee->rsize;
> +        if (ee->eightbit) {
>              DPRINTK("Set pointer %04x\n", ee->cur);
>          }
> +        return 0;
> +    } else if (ee->haveaddr < 2) {
> +        if (!ee->eightbit) {
> +            ee->cur <<= 8;
> +            ee->cur |= data;
> +            ee->haveaddr++;
> +            if (ee->haveaddr == 2) {
> +                ee->cur %= ee->rsize;
> +                DPRINTK("Set pointer %04x\n", ee->cur);
> +            }
>
> -    } else {
> -        if (ee->writable) {
> -            DPRINTK("Send %02x\n", data);
> -            ee->mem[ee->cur] = data;
> -            ee->changed = true;
> -        } else {
> -            DPRINTK("Send error %02x read-only\n", data);
> +            return 0;
>          }
> -        ee->cur = (ee->cur + 1u) % ee->rsize;
> +    }
>
> +    if (ee->writable) {
> +        DPRINTK("Send %02x\n", data);
> +        ee->mem[ee->cur] = data;
> +        ee->changed = true;
> +    } else {
> +        DPRINTK("Send error %02x read-only\n", data);
>      }
> +    ee->cur = (ee->cur + 1u) % ee->rsize;
>
>      return 0;
>  }
> @@ -131,12 +142,16 @@ static void at24c_eeprom_realize(DeviceState *dev,
> Error **errp)
>      EEPROMState *ee = AT24C_EE(dev);
>
>      if (ee->blk) {
> +        /* blk length is a minimum of 1 sector. */
>          int64_t len = blk_getlength(ee->blk);
>
>          if (len != ee->rsize) {
> -            error_setg(errp, "%s: Backing file size %" PRId64 " != %u",
> -                       TYPE_AT24C_EE, len, ee->rsize);
> -            return;
> +            /* for the at24c01 and at24c02, they are smaller than a
> sector. */
> +            if (ee->rsize >= BDRV_SECTOR_SIZE) {
> +                error_setg(errp, "%s: Backing file size %" PRId64 " !=
> %u",
> +                           TYPE_AT24C_EE, len, ee->rsize);
> +                return;
> +            }
>          }
>
>          if (blk_set_perm(ee->blk, BLK_PERM_CONSISTENT_READ |
> BLK_PERM_WRITE,
> @@ -148,6 +163,9 @@ static void at24c_eeprom_realize(DeviceState *dev,
> Error **errp)
>          }
>      }
>
> +    if (ee->rsize < 512) {
> +        ee->eightbit = true;
> +    }
>

Why 512?  The eeprom sizes for the parts seem to grow exponentially, so c01
is 128, then c02 is 256, then 512.  So I check for the two smaller
effectively.  Might warrant a comment.


>      ee->mem = g_malloc0(ee->rsize);
>  }
>
> --
> 2.35.1.723.g4982287a31-goog
>
>

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