Date:   Fri, 5 Oct 2018 04:31:17 +0000
From:   Pankaj Bansal <pankaj.bansal@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexandru Marginean <alexandru.marginean@....com>
Subject: RE: [PATCH 2/2] netdev/phy: add MDIO bus multiplexer driven by a
 regmap

Hi Andrew

> -----Original Message-----
> From: Andrew Lunn [mailto:andrew@...n.ch]
> Sent: Friday, October 5, 2018 9:22 AM
> To: Pankaj Bansal <pankaj.bansal@....com>
> Cc: Florian Fainelli <f.fainelli@...il.com>; netdev@...r.kernel.org;
> Alexandru Marginean <alexandru.marginean@....com>
> Subject: Re: [PATCH 2/2] netdev/phy: add MDIO bus multiplexer driven by a
> regmap
> 
> On Fri, Oct 05, 2018 at 01:59:26PM +0530, Pankaj Bansal wrote:
> > Add support for an MDIO bus multiplexer controlled by a regmap device,
> > like an FPGA.
> >
> > Tested on a NXP LX2160AQDS board which uses the "QIXIS" FPGA
> attached
> > to the i2c bus.
> >
> > Signed-off-by: Pankaj Bansal <pankaj.bansal@....com>
> > ---
> >  drivers/net/phy/Kconfig           |  13 ++
> >  drivers/net/phy/Makefile          |   1 +
> >  drivers/net/phy/mdio-mux-regmap.c | 177
> ++++++++++++++++++++++++++++
> >  3 files changed, 191 insertions(+)
> >
> > diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig index
> > 82070792edbb..bb894ede7464 100644
> > --- a/drivers/net/phy/Kconfig
> > +++ b/drivers/net/phy/Kconfig
> > @@ -87,6 +87,19 @@ config MDIO_BUS_MUX_MMIOREG
> >
> >  	  Currently, only 8/16/32 bits registers are supported.
> >
> > +config MDIO_BUS_MUX_REGMAP
> > +	tristate "REGMAP controlled MDIO bus multiplexers"
> > +	depends on OF_MDIO && HAS_IOMEM
> 
> Hi Pankaj
> 
> Doesn't it also depend on REGMAP?


I will add

> 
> > +	select MDIO_BUS_MUX
> > +	help
> > +	  This module provides a driver for MDIO bus multiplexers that
> > +	  are controlled via a regmap, like an FPGA.
> > +	  The multiplexer connects one of several child MDIO busses to a
> > +	  parent bus.  Child bus selection is under the control of one of
> > +	  the FPGA's registers.
> > +
> > +	  Currently, only upto 32 bits registers are supported.
> > +
> >  config MDIO_CAVIUM
> >  	tristate
> >
> > diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile index
> > 5805c0b7d60e..33053f9f320d 100644
> > --- a/drivers/net/phy/Makefile
> > +++ b/drivers/net/phy/Makefile
> > @@ -29,6 +29,7 @@ obj-$(CONFIG_MDIO_BUS_MUX)	+= mdio-
> mux.o
> >  obj-$(CONFIG_MDIO_BUS_MUX_BCM_IPROC)	+= mdio-mux-bcm-
> iproc.o
> >  obj-$(CONFIG_MDIO_BUS_MUX_GPIO)	+= mdio-mux-gpio.o
> >  obj-$(CONFIG_MDIO_BUS_MUX_MMIOREG) += mdio-mux-mmioreg.o
> > +obj-$(CONFIG_MDIO_BUS_MUX_REGMAP) += mdio-mux-regmap.o
> >  obj-$(CONFIG_MDIO_CAVIUM)	+= mdio-cavium.o
> >  obj-$(CONFIG_MDIO_GPIO)		+= mdio-gpio.o
> >  obj-$(CONFIG_MDIO_HISI_FEMAC)	+= mdio-hisi-femac.o
> > diff --git a/drivers/net/phy/mdio-mux-regmap.c
> > b/drivers/net/phy/mdio-mux-regmap.c
> > new file mode 100644
> > index 000000000000..b0882273fd47
> > --- /dev/null
> > +++ b/drivers/net/phy/mdio-mux-regmap.c
> > @@ -0,0 +1,177 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +
> > +/* Simple regmap based MDIO MUX driver
> > + *
> > + * Copyright 2018 NXP
> > + *
> > + * Based on mdio-mux-mmioreg.c by Timur Tabi
> > + *
> > + * Author:
> > + *     Pankaj Bansal <pankaj.bansal@....com>
> > + */
> > +
> > +#include <linux/platform_device.h>
> > +#include <linux/device.h>
> > +#include <linux/of_mdio.h>
> > +#include <linux/module.h>
> > +#include <linux/phy.h>
> > +#include <linux/mdio-mux.h>
> > +#include <linux/regmap.h>
> > +
> > +struct mdio_mux_regmap_state {
> > +	void		*mux_handle;
> > +	struct regmap	*regmap;
> > +	u32		mux_reg;
> > +	u32		mask;
> > +};
> > +
> > +/* MDIO multiplexing switch function
> > + *
> > + * This function is called by the mdio-mux layer when it thinks the
> > +mdio bus
> > + * multiplexer needs to switch.
> > + *
> > + * 'current_child' is the current value of the mux register (masked
> > +via
> > + * s->mask).
> > + *
> > + * 'desired_child' is the value of the 'reg' property of the target
> > +child MDIO
> > + * node.
> > + *
> > + * The first time this function is called, current_child == -1.
> > + *
> > + * If current_child == desired_child, then the mux is already set to
> > +the
> > + * correct bus.
> > + */
> > +static int mdio_mux_regmap_switch_fn(int current_child, int
> desired_child,
> > +				     void *data)
> > +{
> > +	struct mdio_mux_regmap_state *s = data;
> > +	bool change;
> > +	int ret = 0;
> > +
> 
> No need to initialise ret.

Ok

> 
> > +	ret = regmap_update_bits_check(s->regmap,
> > +				       s->mux_reg,
> > +				       s->mask,
> > +				       desired_child,
> > +				       &change);
> 
> When getting the mask from DT, you use be32_to_cpup().
> When testing the reg value against the mask, you use be32_to_cpup().
> Here you do not use be32_to_cpup()?

Can you please tell me for which variable you mean I should use be32_to_cpup?
I use be32_to_cpup when reading device tree entries.
After being read, their values are stored in structure. After that no need to do be32_to_cpup

> 
> > +
> > +	if (ret)
> > +		goto out;
> 
> Just do the return here.

Ok

> 
> > +	if (change)
> > +		pr_debug("%s %d -> %d\n", __func__, current_child,
> > +			 desired_child);
> > +
> > +out:
> > +	return ret;
> > +}
> > +
> > +static int mdio_mux_regmap_probe(struct platform_device *pdev) {
> > +	struct device_node *np2, *np = pdev->dev.of_node;
> > +	struct mdio_mux_regmap_state *s;
> > +	const __be32 *iprop;
> > +	int len, ret;
> > +	u32 val;
> > +
> > +	dev_dbg(&pdev->dev, "probing node %pOF\n", np);
> > +
> > +	s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
> > +	if (!s)
> > +		return -ENOMEM;
> > +
> > +	s->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> > +	if (IS_ERR(s->regmap)) {
> > +		dev_err(&pdev->dev, "Failed to get parent regmap\n");
> > +		ret = PTR_ERR(s->regmap);
> > +		return ret;
> 
> return PTR_ERR(s->regmap);

Ok

> 
> > +	}
> > +
> > +	iprop = of_get_property(np, "reg", &len);
> > +	if (!iprop || len != sizeof(u32)) {
> > +		dev_err(&pdev->dev, "missing or invalid reg property\n");
> > +		return -ENODEV;
> > +	}
> > +	s->mux_reg = (u32)be32_to_cpup(iprop);
> > +
> > +	/* Test Register read write */
> > +	ret = regmap_read(s->regmap, s->mux_reg, &val);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "error while reading reg\n");
> > +		return ret;
> > +	}
> > +
> > +	ret = regmap_write(s->regmap, s->mux_reg, val);
> > +	if (ret) {
> > +		dev_err(&pdev->dev, "error while writing reg\n");
> > +		return ret;
> > +	}
> > +
> > +	iprop = of_get_property(np, "mux-mask", &len);
> > +	if (!iprop || len != sizeof(u32)) {
> > +		dev_err(&pdev->dev, "missing or invalid mux-mask
> property\n");
> > +		return -ENODEV;
> > +	}
> > +	s->mask = (uint32_t)be32_to_cpup(iprop);
> 
> Is this cast needed?

I will remove the typecasts.

> 
> > +
> > +	/* Verify that the 'reg' property of each child MDIO bus does not
> > +	 * set any bits outside of the 'mask'.
> > +	 */
> > +	for_each_available_child_of_node(np, np2) {
> > +		iprop = of_get_property(np2, "reg", &len);
> > +		if (!iprop || len != sizeof(u32)) {
> > +			dev_err(&pdev->dev, "mdio-mux child node %pOF is
> missing a 'reg' property\n", np2);
> > +			of_node_put(np2);
> > +			return -ENODEV;
> > +		}
> > +		if (be32_to_cpup(iprop) & ~s->mask) {
> > +			dev_err(&pdev->dev, "mdio-mux child node %pOF
> has a 'reg' value with unmasked bits\n", np2);
> > +			of_node_put(np2);
> > +			return -ENODEV;
> > +		}
> > +	}
> > +
> > +	ret = mdio_mux_init(&pdev->dev, pdev->dev.of_node,
> > +			    mdio_mux_regmap_switch_fn,
> > +			    &s->mux_handle, s, NULL);
> > +	if (ret) {
> > +		if (ret != -EPROBE_DEFER)
> > +			dev_err(&pdev->dev,
> > +				"failed to register mdio-mux bus %pOF\n",
> np);
> > +		return ret;
> > +	}
> > +
> > +	pdev->dev.platform_data = s;
> > +	return 0;
> > +}
> > +
> > +static int mdio_mux_regmap_remove(struct platform_device *pdev) {
> > +	struct mdio_mux_regmap_state *s = dev_get_platdata(&pdev-
> >dev);
> > +
> > +	mdio_mux_uninit(s->mux_handle);
> > +
> > +	return 0;
> > +}
> > +
> > +static const struct of_device_id mdio_mux_regmap_match[] = {
> > +	{
> > +		.compatible = "mdio-mux-regmap",
> > +	},
> > +	{},
> > +};
> > +MODULE_DEVICE_TABLE(of, mdio_mux_regmap_match);
> > +
> > +static struct platform_driver mdio_mux_regmap_driver = {
> > +	.driver = {
> > +		.name		= "mdio-mux-regmap",
> > +		.of_match_table = mdio_mux_regmap_match,
> > +	},
> > +	.probe		= mdio_mux_regmap_probe,
> > +	.remove		= mdio_mux_regmap_remove,
> > +};
> > +
> > +module_platform_driver(mdio_mux_regmap_driver);
> > +
> > +MODULE_AUTHOR("Pankaj Bansal <pankaj.bansal@....com>");
> > +MODULE_DESCRIPTION("I2c device MDIO MUX driver");
> 
> I2C should be replaced by regmap.

Nice catch. I will replace it.

> 
>     Andrew

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