Re: [net-next 3/3] net: mdio: aspeed: Add dummy read for fire control

[Andrew Jeffery <andrew@codeconstruct.com.au>]

Hi Jacky,

On Mon, 2024-11-18 at 18:47 +0800, Jacky Chou wrote:
> Add a dummy read to ensure triggering mdio controller before starting
> polling the status of mdio controller.
> 
> Signed-off-by: Jacky Chou <jacky_chou@aspeedtech.com>
> ---
>  drivers/net/mdio/mdio-aspeed.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/mdio/mdio-aspeed.c b/drivers/net/mdio/mdio-
> aspeed.c
> index 4d5a115baf85..feae30bc3e78 100644
> --- a/drivers/net/mdio/mdio-aspeed.c
> +++ b/drivers/net/mdio/mdio-aspeed.c
> @@ -62,6 +62,8 @@ static int aspeed_mdio_op(struct mii_bus *bus, u8
> st, u8 op, u8 phyad, u8 regad,
>                 | FIELD_PREP(ASPEED_MDIO_DATA_MIIRDATA, data);
>  
>         iowrite32(ctrl, ctx->base + ASPEED_MDIO_CTRL);
> +       /* Add dummy read to ensure triggering mdio controller */
> +       (void)ioread32(ctx->base + ASPEED_MDIO_CTRL);

Why do this when the same register is immediately read by
readl_poll_timeout() below?

If there is a reason, I'd like some more explanation in the comment
you've added, discussing the details of the problem it's solving when
taking into account the readl_poll_timeout() call.

>  
>         return readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl,
>                                 !(ctrl & ASPEED_MDIO_CTRL_FIRE),

Cheers,

Andrew