Re: [net-next,v3 2/2] net: phy: sfp: enable i2c-bus detection on ACPI based systems

[Russell King - ARM Linux admin]

On Mon, May 27, 2019 at 08:22:13PM -0700, Ruslan Babayev wrote:
> Lookup I2C adapter using the "i2c-bus" device property on ACPI based
> systems similar to how it's done with DT.
> 
> An example DSD describing an SFP on an ACPI based system:
> 
> Device (SFP0)
> {
>     Name (_HID, "PRP0001")
>     Name (_CRS, ResourceTemplate()
>     {
>         GpioIo(Exclusive, PullDefault, 0, 0, IoRestrictionNone,
>                "\\_SB.PCI0.RP01.GPIO", 0, ResourceConsumer)
>             { 0, 1, 2, 3, 4 }
>     })
>     Name (_DSD, Package ()
>     {
>         ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>         Package () {
>             Package () { "compatible", "sff,sfp" },
>             Package () { "i2c-bus", \_SB.PCI0.RP01.I2C.MUX.CH0 },
>             Package () { "maximum-power-milliwatt", 1000 },
>             Package () { "tx-disable-gpios", Package () { ^SFP0, 0, 0, 1} },
>             Package () { "reset-gpio",       Package () { ^SFP0, 0, 1, 1} },
>             Package () { "mod-def0-gpios",   Package () { ^SFP0, 0, 2, 1} },
>             Package () { "tx-fault-gpios",   Package () { ^SFP0, 0, 3, 0} },
>             Package () { "los-gpios",        Package () { ^SFP0, 0, 4, 1} },
>         },
>     })
> }
> 
> Device (PHY0)
> {
>     Name (_HID, "PRP0001")
>     Name (_DSD, Package ()
>     {
>         ToUUID ("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
>         Package () {
>             Package () { "compatible", "ethernet-phy-ieee802.3-c45" },
>             Package () { "sfp", \_SB.PCI0.RP01.SFP0 },
>             Package () { "managed", "in-band-status" },
>             Package () { "phy-mode", "sgmii" },
>         },
>     })
> }
> 
> Signed-off-by: Ruslan Babayev <ruslan@xxxxxxxxxxx>
> Cc: xe-linux-external@xxxxxxxxx

Looks mostly fine to me, thanks.  A few comments below, mostly minor.
The way we handle the non-DT and non-ACPI case needs addressing though.

> ---
>  drivers/net/phy/sfp.c | 33 +++++++++++++++++++++++++--------
>  1 file changed, 25 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
> index d4635c2178d1..7a6c8df8899b 100644
> --- a/drivers/net/phy/sfp.c
> +++ b/drivers/net/phy/sfp.c
> @@ -9,6 +9,7 @@
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/of.h>
> +#include <linux/acpi.h>
>  #include <linux/phy.h>
>  #include <linux/platform_device.h>
>  #include <linux/rtnetlink.h>

These includes are arranged in alphabetical order, is there a reason
why we need acpi.h out of order here?

> @@ -1783,6 +1784,7 @@ static int sfp_probe(struct platform_device *pdev)
>  {
>  	const struct sff_data *sff;
>  	struct sfp *sfp;
> +	struct i2c_adapter *i2c = NULL;

Please move this one line above, I think that will be neater.

I'm also debating whether we should have it initialised to null - see
below.

>  	bool poll = false;
>  	int irq, err, i;
>  
> @@ -1801,7 +1803,6 @@ static int sfp_probe(struct platform_device *pdev)
>  	if (pdev->dev.of_node) {
>  		struct device_node *node = pdev->dev.of_node;
>  		const struct of_device_id *id;
> -		struct i2c_adapter *i2c;
>  		struct device_node *np;
>  
>  		id = of_match_node(sfp_of_match, node);
> @@ -1818,14 +1819,30 @@ static int sfp_probe(struct platform_device *pdev)
>  
>  		i2c = of_find_i2c_adapter_by_node(np);
>  		of_node_put(np);
> -		if (!i2c)
> -			return -EPROBE_DEFER;
> -
> -		err = sfp_i2c_configure(sfp, i2c);
> -		if (err < 0) {
> -			i2c_put_adapter(i2c);
> -			return err;
> +	} else if (ACPI_COMPANION(&pdev->dev)) {
> +		struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
> +		struct fwnode_handle *fw = acpi_fwnode_handle(adev);
> +		struct fwnode_reference_args args;
> +		struct acpi_handle *acpi_handle;
> +		int ret;
> +
> +		ret = acpi_node_get_property_reference(fw, "i2c-bus", 0, &args);
> +		if (ACPI_FAILURE(ret) || !is_acpi_device_node(args.fwnode)) {
> +			dev_err(&pdev->dev, "missing 'i2c-bus' property\n");
> +			return -ENODEV;
>  		}
> +
> +		acpi_handle = ACPI_HANDLE_FWNODE(args.fwnode);
> +		i2c = i2c_acpi_find_adapter_by_handle(acpi_handle);
> +	}

If we don't have DT, and we don't have ACPI, there isn't a way that
we can find the I2C adapter, so I think we probably ought to fail the
probe here, rather than...

> +
> +	if (!i2c)
> +		return -EPROBE_DEFER;

deferring in that case.  So, basically:

	struct i2c_adapter *i2c;

	if (pdev->dev.of_node) {
		...
	} else if (ACPI_COMPANION(&pdev->dev)) {
		...
	} else {
		return -EINVAL;
	}

	if (!i2c)
		return -EPROBE_DEFER;

> +
> +	err = sfp_i2c_configure(sfp, i2c);
> +	if (err < 0) {
> +		i2c_put_adapter(i2c);
> +		return err;
>  	}
>  
>  	for (i = 0; i < GPIO_MAX; i++)
> -- 
> 2.19.2
> 
> 

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