linux-kernel - Re: [PATCH net-next v3 1/4] net: mdio: Introduce a regmap-based mdio driver

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Date:   Fri, 26 May 2023 13:21:39 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc:     Mark Brown <broonie@...nel.org>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        alexis.lothore@...tlin.com, thomas.petazzoni@...tlin.com,
        Andrew Lunn <andrew@...n.ch>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Ioana Ciornei <ioana.ciornei@....com>,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Jose Abreu <joabreu@...opsys.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Simon Horman <simon.horman@...igine.com>
Subject: Re: [PATCH net-next v3 1/4] net: mdio: Introduce a regmap-based mdio
 driver

On Fri, May 26, 2023 at 09:42:49AM +0200, Maxime Chevallier wrote:
> There exists several examples today of devices that embed an ethernet
> PHY or PCS directly inside an SoC. In this situation, either the device
> is controlled through a vendor-specific register set, or sometimes
> exposes the standard 802.3 registers that are typically accessed over
> MDIO.
> 
> As phylib and phylink are designed to use mdiodevices, this driver
> allows creating a virtual MDIO bus, that translates mdiodev register
> accesses to regmap accesses.
> 
> The reason we use regmap is because there are at least 3 such devices
> known today, 2 of them are Altera TSE PCS's, memory-mapped, exposed
> with a 4-byte stride in stmmac's dwmac-socfpga variant, and a 2-byte
> stride in altera-tse. The other one (nxp,sja1110-base-tx-mdio) is
> exposed over SPI.
> 
> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
> ---
> V2->V3 :
>  - Introduce struct miod_regmap_priv for priv elements instead of plain
>    reuse of the config struct
>  - Use ~O instead of ~0UL
> V1->V2 :
>  - Use phy_mask to avoid unnecessary scanning, suggested by Andrew
>  - Allow entirely disabling scanning, suggested by Vlad
> 
>  MAINTAINERS                         |  7 +++
>  drivers/net/ethernet/altera/Kconfig |  2 +
>  drivers/net/mdio/Kconfig            | 10 ++++
>  drivers/net/mdio/Makefile           |  1 +
>  drivers/net/mdio/mdio-regmap.c      | 93 +++++++++++++++++++++++++++++
>  include/linux/mdio/mdio-regmap.h    | 24 ++++++++
>  6 files changed, 137 insertions(+)
>  create mode 100644 drivers/net/mdio/mdio-regmap.c
>  create mode 100644 include/linux/mdio/mdio-regmap.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index c904dba1733b..f68269b39e09 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -12835,6 +12835,13 @@ F:	Documentation/devicetree/bindings/net/ieee802154/mcr20a.txt
>  F:	drivers/net/ieee802154/mcr20a.c
>  F:	drivers/net/ieee802154/mcr20a.h
>  
> +MDIO REGMAP DRIVER
> +M:	Maxime Chevallier <maxime.chevallier@...tlin.com>
> +L:	netdev@...r.kernel.org
> +S:	Maintained
> +F:	drivers/net/mdio/mdio-regmap.c
> +F:	include/linux/mdio/mdio-regmap.h
> +
>  MEASUREMENT COMPUTING CIO-DAC IIO DRIVER
>  M:	William Breathitt Gray <william.gray@...aro.org>
>  L:	linux-iio@...r.kernel.org
> diff --git a/drivers/net/ethernet/altera/Kconfig b/drivers/net/ethernet/altera/Kconfig
> index dd7fd41ccde5..0a7c0a217536 100644
> --- a/drivers/net/ethernet/altera/Kconfig
> +++ b/drivers/net/ethernet/altera/Kconfig
> @@ -5,6 +5,8 @@ config ALTERA_TSE
>  	select PHYLIB
>  	select PHYLINK
>  	select PCS_ALTERA_TSE
> +	select MDIO_REGMAP
> +	depends on REGMAP

I don't think this bit belongs in this patch.
Also: depends on REGMAP or select REGMAP?

>  	help
>  	  This driver supports the Altera Triple-Speed (TSE) Ethernet MAC.
>  
> diff --git a/drivers/net/mdio/Kconfig b/drivers/net/mdio/Kconfig
> index 9ff2e6f22f3f..aef39c89cf44 100644
> --- a/drivers/net/mdio/Kconfig
> +++ b/drivers/net/mdio/Kconfig
> @@ -185,6 +185,16 @@ config MDIO_IPQ8064
>  	  This driver supports the MDIO interface found in the network
>  	  interface units of the IPQ8064 SoC
>  
> +config MDIO_REGMAP
> +	tristate
> +	help
> +	  This driver allows using MDIO devices that are not sitting on a
> +	  regular MDIO bus, but still exposes the standard 802.3 register
> +	  layout. It's regmap-based so that it can be used on integrated,
> +	  memory-mapped PHYs, SPI PHYs and so on. A new virtual MDIO bus is
> +	  created, and its read/write operations are mapped to the underlying
> +	  regmap.

It would probably be helpful to state that those who select this option
should also explicitly select REGMAP.

> +
>  config MDIO_THUNDER
>  	tristate "ThunderX SOCs MDIO buses"
>  	depends on 64BIT
> diff --git a/drivers/net/mdio/Makefile b/drivers/net/mdio/Makefile
> index 7d4cb4c11e4e..1015f0db4531 100644
> --- a/drivers/net/mdio/Makefile
> +++ b/drivers/net/mdio/Makefile
> @@ -19,6 +19,7 @@ obj-$(CONFIG_MDIO_MOXART)		+= mdio-moxart.o
>  obj-$(CONFIG_MDIO_MSCC_MIIM)		+= mdio-mscc-miim.o
>  obj-$(CONFIG_MDIO_MVUSB)		+= mdio-mvusb.o
>  obj-$(CONFIG_MDIO_OCTEON)		+= mdio-octeon.o
> +obj-$(CONFIG_MDIO_REGMAP)		+= mdio-regmap.o
>  obj-$(CONFIG_MDIO_SUN4I)		+= mdio-sun4i.o
>  obj-$(CONFIG_MDIO_THUNDER)		+= mdio-thunder.o
>  obj-$(CONFIG_MDIO_XGENE)		+= mdio-xgene.o
> diff --git a/include/linux/mdio/mdio-regmap.h b/include/linux/mdio/mdio-regmap.h
> new file mode 100644
> index 000000000000..b8508f152552
> --- /dev/null
> +++ b/include/linux/mdio/mdio-regmap.h
> @@ -0,0 +1,24 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/* Driver for MMIO-Mapped MDIO devices. Some IPs expose internal PHYs or PCS
> + * within the MMIO-mapped area
> + *
> + * Copyright (C) 2023 Maxime Chevallier <maxime.chevallier@...tlin.com>
> + */
> +#ifndef MDIO_REGMAP_H
> +#define MDIO_REGMAP_H
> +
> +struct device;
> +struct regmap;
> +
> +struct mdio_regmap_config {
> +	struct device *parent;
> +	struct regmap *regmap;
> +	char name[MII_BUS_ID_SIZE];

don't we need a header included for the MII_BUS_ID_SIZE macro?
An empty C file which includes just <linux/mdio/mdio-regmap.h> must
build without errors.

> +	u8 valid_addr;
> +	bool autoscan;
> +};
> +
> +struct mii_bus *devm_mdio_regmap_register(struct device *dev,
> +					  const struct mdio_regmap_config *config);
> +
> +#endif
> -- 
> 2.40.1
>