Re: [PATCH 3/4] net: mediatek: sgmii: mtk_pcs_setup_mode_an: don't rely on register defaults

[Alexander 'lynxis' Couzens <lynxis@fe80.eu>]

On Tue, 23 Aug 2022 16:28:47 +0100
"Russell King (Oracle)" <linux@armlinux.org.uk> wrote:

> On Sun, Aug 21, 2022 at 12:45:37AM +0200, Alexander Couzens wrote:
> > Ensure autonegotiation is enabled.
> > 
> > Signed-off-by: Alexander Couzens <lynxis@fe80.eu>
> > ---
> >  drivers/net/ethernet/mediatek/mtk_sgmii.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/mediatek/mtk_sgmii.c
> > b/drivers/net/ethernet/mediatek/mtk_sgmii.c index
> > 782812434367..aa69baf1a42f 100644 ---
> > a/drivers/net/ethernet/mediatek/mtk_sgmii.c +++
> > b/drivers/net/ethernet/mediatek/mtk_sgmii.c @@ -32,12 +32,13 @@
> > static int mtk_pcs_setup_mode_an(struct mtk_pcs *mpcs)
> > regmap_write(mpcs->regmap, SGMSYS_PCS_LINK_TIMER,
> > SGMII_LINK_TIMER_DEFAULT); 
> > +	/* disable remote fault & enable auto neg */
> >  	regmap_read(mpcs->regmap, SGMSYS_SGMII_MODE, &val);
> > -	val |= SGMII_REMOTE_FAULT_DIS;
> > +	val |= SGMII_REMOTE_FAULT_DIS | SGMII_SPEED_DUPLEX_AN;  
> 
> Does SGMII_SPEED_DUPLEX_AN need to be cleared in
> mtk_pcs_setup_mode_force(), so mtk_pcs_link_up() can force the
> duplex setting for base-X protocols?
> 

Yes SGMII_SPEED_DUPLEX_AN needs to be cleared to have FORCE_DUPLEX
working. But mtk_pcs_setup_mode_force() is clearing it implicit by

val &= SGMII_DUPLEX_FULL & ~SGMII_IF_MODE_MASK

because it's included in the SGMII_IF_MODE_MASK.
I also don't understand why it's forcing it in the
mtk_pcs_link_up().