linux-kernel - Re: [PATCH RFC net-next v2 17/17] net: stmmac: pcs: Drop the

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Date: Fri, 28 Jun 2024 15:42:41 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Serge Semin <fancer.lancer@...il.com>
Cc: Andrew Halaney <ahalaney@...hat.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	linux-arm-kernel@...ts.infradead.org,
	linux-stm32@...md-mailman.stormreply.com, bpf@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC net-next v2 17/17] net: stmmac: pcs: Drop the _SHIFT
 macros

On Mon, Jun 24, 2024 at 04:26:34PM +0300, Serge Semin wrote:
> The PCS_ANE_PSE_SHIFT and PCS_ANE_RFE_SHIFT are unused anyway. Moreover
> PCS_ANE_PSE and PCS_ANE_RFE are the respective field masks. So the
> FIELD_GET()/FIELD_SET() macro-functions can be used to get/set the fields
> content. Drop the _SHIFT macros for good then.
> 
> Signed-off-by: Serge Semin <fancer.lancer@...il.com>
> ---
>  drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
> index a17e5b37c411..0f15c9898788 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_pcs.h
> @@ -43,9 +43,7 @@
>  #define PCS_ANE_FD		BIT(5)		/* AN Full-duplex flag */
>  #define PCS_ANE_HD		BIT(6)		/* AN Half-duplex flag */
>  #define PCS_ANE_PSE		GENMASK(8, 7)	/* AN Pause Encoding */
> -#define PCS_ANE_PSE_SHIFT	7
>  #define PCS_ANE_RFE		GENMASK(13, 12)	/* AN Remote Fault Encoding */
> -#define PCS_ANE_RFE_SHIFT	12
>  #define PCS_ANE_ACK		BIT(14)		/* AN Base-page acknowledge */

I would actually like to see all these go away.

PCS_ANE_FD == LPA_1000XFULL
PCS_ANE_HD == LPA_1000XHALF
PCS_ANE_PSE == LPA_1000XPAUSE and LPA_1000XPAUSE_ASYM
PCS_ANE_RFE == LPA_RESV and LPA_RFAULT
PCS_ANE_ACK == LPA_LPACK

Isn't it rather weird that the field layout matches 802.3z aka
1000base-X and not SGMII? This layout would not make sense for Cisco
SGMII as it loses the speed information conveyed by the Cisco SGMII
control word.

This isn't a case of the manufacturer using "SGMII" to mean a serial
gigabit media independent interface that supports 1000base-X
(PHY_INTERFACE_MODE_1000BASEX) rather than Cisco SGMII
(PHY_INTERFACE_MODE_SGMII) ?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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