netdev - Re: [PATCH] net: stmmac: Fix unset max_speed difference between DT and non-DT platforms

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Date:   Thu, 31 Mar 2022 11:34:54 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Chen-Yu Tsai <wens@...nel.org>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>, Chen-Yu Tsai <wens@...e.org>,
        Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] net: stmmac: Fix unset max_speed difference between DT
 and non-DT platforms

On Fri,  1 Apr 2022 01:18:27 +0800 Chen-Yu Tsai wrote:
> From: Chen-Yu Tsai <wens@...e.org>
> 
> In commit 9cbadf094d9d ("net: stmmac: support max-speed device tree
> property"), when DT platforms don't set "max-speed", max_speed is set to
> -1; for non-DT platforms, it stays the default 0.
> 
> Prior to commit eeef2f6b9f6e ("net: stmmac: Start adding phylink support"),
> the check for a valid max_speed setting was to check if it was greater
> than zero. This commit got it right, but subsequent patches just checked
> for non-zero, which is incorrect for DT platforms.
> 
> In commit 92c3807b9ac3 ("net: stmmac: convert to phylink_get_linkmodes()")
> the conversion switched completely to checking for non-zero value as a
> valid value, which caused 1000base-T to stop getting advertised by
> default.
> 
> Instead of trying to fix all the checks, simply leave max_speed alone if
> DT property parsing fails.
> 
> Fixes: 9cbadf094d9d ("net: stmmac: support max-speed device tree property")
> Fixes: 92c3807b9ac3 ("net: stmmac: convert to phylink_get_linkmodes()")
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>
> ---

You should always CC authors of patches you put on CC as they have 
the most context to review, usually. Please use get_maintainers.pl
and repost.

> This was first noticed on ROC-RK3399-PC, and also observed on ROC-RK3328-CC.
> The fix was tested on ROC-RK3328-CC and Libre Computer ALL-H5-ALL-CC.
> 
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> index 5d29f336315b..11e1055e8260 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
> @@ -431,8 +431,7 @@ stmmac_probe_config_dt(struct platform_device *pdev, u8 *mac)
>  	plat->phylink_node = np;
>  
>  	/* Get max speed of operation from device tree */
> -	if (of_property_read_u32(np, "max-speed", &plat->max_speed))
> -		plat->max_speed = -1;
> +	of_property_read_u32(np, "max-speed", &plat->max_speed);
>  
>  	plat->bus_id = of_alias_get_id(np, "ethernet");
>  	if (plat->bus_id < 0)