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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0d53f5fbb6b3f1eb01e601255f7e5ee3d1c45f93.camel@codeconstruct.com.au>
Date: Tue, 19 Nov 2024 09:35:39 +1030
From: Andrew Jeffery <andrew@...econstruct.com.au>
To: Jacky Chou <jacky_chou@...eedtech.com>, andrew+netdev@...n.ch, 
 davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com,  robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, joel@....id.au,  hkallweit1@...il.com,
 linux@...linux.org.uk, netdev@...r.kernel.org,  devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org,  linux-aspeed@...ts.ozlabs.org,
 linux-kernel@...r.kernel.org
Subject: Re: [net-next 3/3] net: mdio: aspeed: Add dummy read for fire
 control

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@...eedtech.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