Re: [PATCH net] net: dsa: lantiq_gswip: Let GSWIP automatically set the xMII clock

[Florian Fainelli <f.fainelli@gmail.com>]

On 3/24/2021 12:36 PM, Martin Blumenstingl wrote:
> The xMII interface clock depends on the PHY interface (MII, RMII, RGMII)
> as well as the current link speed. Explicitly configure the GSWIP to
> automatically select the appropriate xMII interface clock.
> 
> This fixes an issue seen by some users where ports using an external
> RMII or RGMII PHY were deaf (no RX or TX traffic could be seen). Most
> likely this is due to an "invalid" xMII clock being selected either by
> the bootloader or hardware-defaults.
> 
> Fixes: 14fceff4771e51 ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>

> ---
> It would be great to have this fix backported to Linux 5.4 and 5.10 to
> get rid of one more blocker which prevents OpenWrt from switching to
> this new in-tree driver.

Given there is a Fixes: tag this should land at some point in the stable
tree auto-selection. Stable fixes for networking patches follows a
slightly different path:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/networking/netdev-FAQ.rst#n145

> 
> 
>  drivers/net/dsa/lantiq_gswip.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/lantiq_gswip.c b/drivers/net/dsa/lantiq_gswip.c
> index 52e865a3912c..809dfa3be6bb 100644
> --- a/drivers/net/dsa/lantiq_gswip.c
> +++ b/drivers/net/dsa/lantiq_gswip.c
> @@ -799,10 +799,15 @@ static int gswip_setup(struct dsa_switch *ds)
>  	/* Configure the MDIO Clock 2.5 MHz */
>  	gswip_mdio_mask(priv, 0xff, 0x09, GSWIP_MDIO_MDC_CFG1);
>  
> -	/* Disable the xMII link */
> -	for (i = 0; i < priv->hw_info->max_ports; i++)
> +	for (i = 0; i < priv->hw_info->max_ports; i++) {
> +		/* Disable the xMII link */
>  		gswip_mii_mask_cfg(priv, GSWIP_MII_CFG_EN, 0, i);
>  
> +		/* Automatically select the xMII interface clock */
> +		gswip_mii_mask_cfg(priv, GSWIP_MII_CFG_RATE_MASK,
> +				   GSWIP_MII_CFG_RATE_AUTO, i);
> +	}
> +
>  	/* enable special tag insertion on cpu port */
>  	gswip_switch_mask(priv, 0, GSWIP_FDMA_PCTRL_STEN,
>  			  GSWIP_FDMA_PCTRLp(cpu_port));
> 

-- 
Florian