netdev - Re: [Uclinux-dist-devel] [PATCH 2/2] net: dsa: introduce MICREL KSZ8893MQL/BL ethernet switch chip support

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Date:	Wed, 21 Jul 2010 22:31:37 +0200
From:	Karl Beldan <karl.beldan@...il.com>
To:	Mike Frysinger <vapier.adi@...il.com>
Cc:	Lennert Buytenhek <buytenh@...tstofly.org>, netdev@...r.kernel.org,
	uclinux-dist-devel@...ckfin.uclinux.org,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [Uclinux-dist-devel] [PATCH 2/2] net: dsa: introduce MICREL 
	KSZ8893MQL/BL ethernet switch chip support

On Wed, Jul 21, 2010 at 6:05 PM, Mike Frysinger <vapier.adi@...il.com> wrote:
> On Wed, Jul 21, 2010 at 11:16, Lennert Buytenhek wrote:
>> On Wed, Jul 21, 2010 at 09:37:22AM -0400, Mike Frysinger wrote:
>>> +static int ksz8893m_setup(struct dsa_switch *ds)
>>> +{
>>> +     int i;
>>> +     int ret;
>>> +
>>> +     ret = ksz8893m_switch_reset(ds);
>>> +     if (ret < 0)
>>> +             return ret;
>>
>> It's pretty ugly that the mdiobus is passed in via the normal means,
>> but a reference to the SPI bus to use is just stuffed into some global
>> variable.
>>
>> Can you not access all registers via MII?
>
> it depends on the host mdio bus.  if it supports the semi-standard
> behavior of toggling the OP field of MDIO frames, then yes, you can do
> it via MII.  but i dont think the current mdio framework in the kernel
> keeps track of that functionality, so there isnt a way in the driver
> to say "is this possible, else fall back to SPI".
>
Are you referring to SMI ?

> certainly the part that was used to develop this driver does not
> support this behavior thus SPI is the only way of accessing the
> extended registers.  i guess the driver could be extended so that
> people could pick which mode they want to program the registers via
> platform resources, but we have no way of testing that, so i say let
> the person who actually can use & wants that functionality implement
> it.
>
>> (If not, struct dsa_chip_data will need go be extended with another
>> struct device pointer that we can use to find the spi bus with.)
>
> if the framework supports, i can convert the driver to it, but i'm not
> sure we have the time atm to tackle reworking common frameworks.
>
If someone tackles this, it would be nice that they bear in mind that
phylib's drivers also need spi/smi/i2c register access.

>>> +static int ksz8893m_port_to_phy_addr(int port)
>>> +{
>>> +     if (port >= 1 && port <= KSZ8893M_PORT_NUM)
>>> +             return port;
>>> +
>>> +     pr_warning("use default phy addr 3\n");
>>> +     return 3;
>>
>> Does this ever happen?  You should just be able to return -1 here, IMHO.
>
> i dont recall seeing a warning, but presumably if it it did occur,
> something else needs fixing.  so -1 is OK.
>
I would remove this.

-- 
Karl
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