Re: [PATCH] hw/net/imx_fec: return 0xffff when accessing non-existing PHY

[Bin Meng]

On Mon, May 3, 2021 at 12:03 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> If a PHY does not exist, attempts to read from it should return 0xffff.
> Otherwise the Linux kernel will believe that a PHY is there and select
> the non-existing PHY. This in turn will result in network errors later
> on since the real PHY is not selected or configured.
>
> Since reading from or writing to a non-existing PHY is not an emulation
> error, replace guest error messages with traces.
>
> Fixes: 461c51ad4275 ("Add a phy-num property to the i.MX FEC emulator")
> Cc: Jean-Christophe Dubois <jcd@tribudubois.net>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  hw/net/imx_fec.c    | 8 +++-----
>  hw/net/trace-events | 2 ++
>  2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/hw/net/imx_fec.c b/hw/net/imx_fec.c
> index f03450c028..9c7035bc94 100644
> --- a/hw/net/imx_fec.c
> +++ b/hw/net/imx_fec.c
> @@ -283,9 +283,8 @@ static uint32_t imx_phy_read(IMXFECState *s, int reg)
>      uint32_t phy = reg / 32;
>
>      if (phy != s->phy_num) {
> -        qemu_log_mask(LOG_GUEST_ERROR, "[%s.phy]%s: Bad phy num %u\n",
> -                      TYPE_IMX_FEC, __func__, phy);
> -        return 0;
> +        trace_imx_phy_read_num(phy, s->phy_num);
> +        return 0xffff;
>      }
>
>      reg %= 32;
> @@ -345,8 +344,7 @@ static void imx_phy_write(IMXFECState *s, int reg, 
> uint32_t val)
>      uint32_t phy = reg / 32;
>
>      if (phy != s->phy_num) {
> -        qemu_log_mask(LOG_GUEST_ERROR, "[%s.phy]%s: Bad phy num %u\n",
> -                      TYPE_IMX_FEC, __func__, phy);
> +        trace_imx_phy_write_num(phy, s->phy_num);
>          return;
>      }
>
> diff --git a/hw/net/trace-events b/hw/net/trace-events
> index baf25ffa7e..ee77238d9e 100644
> --- a/hw/net/trace-events
> +++ b/hw/net/trace-events
> @@ -413,8 +413,10 @@ i82596_set_multicast(uint16_t count) "Added %d multicast 
> entries"
>  i82596_channel_attention(void *s) "%p: Received CHANNEL ATTENTION"
>
>  # imx_fec.c
> +imx_phy_read_num(int phy, int configured) "read request from unconfigured 
> phy %d (configured %d)"

nits: could we put this below imx_phy_read(), like you put
imx_phy_write_num after imx_phy_write?

>  imx_phy_read(uint32_t val, int phy, int reg) "0x%04"PRIx32" <= 
> phy[%d].reg[%d]"
>  imx_phy_write(uint32_t val, int phy, int reg) "0x%04"PRIx32" => 
> phy[%d].reg[%d]"
> +imx_phy_write_num(int phy, int configured) "write request to unconfigured 
> phy %d (configured %d)"
>  imx_phy_update_link(const char *s) "%s"
>  imx_phy_reset(void) ""
>  imx_fec_read_bd(uint64_t addr, int flags, int len, int data) "tx_bd 
> 0x%"PRIx64" flags 0x%04x len %d data 0x%08x"
> --

Otherwise,
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>