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);
 
 	return readl_poll_timeout(ctx->base + ASPEED_MDIO_CTRL, ctrl,
 				!(ctrl & ASPEED_MDIO_CTRL_FIRE),
-- 
2.25.1

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

On Tue, Nov 19, 2024 at 09:35:39AM +1030, Andrew Jeffery wrote:
> 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.

Also, is this a fix? Should it have a Fixes: tag? If so, it should not
be part of this series, assuming the older devices have the same
issue.

	Andrew