netdev - RE: [PATCH v3 net-next 3/5] dsa: add DSA switch driver for Microchip KSZ9477

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Date:   Mon, 22 May 2017 21:21:28 +0000
From:   <Woojung.Huh@...rochip.com>
To:     <andrew@...n.ch>
CC:     <f.fainelli@...il.com>, <vivien.didelot@...oirfairelinux.com>,
        <sergei.shtylyov@...entembedded.com>, <netdev@...r.kernel.org>,
        <davem@...emloft.net>, <UNGLinuxDriver@...rochip.com>
Subject: RE: [PATCH v3 net-next 3/5] dsa: add DSA switch driver for
 Microchip KSZ9477

Hi Andres,

> > +static struct {
> > +	int index;
> > +	char string[ETH_GSTRING_LEN];
> 
> Hi Woojung
> 
> Since you need to respin for the skb_put_padto(), please make this
> const.
OK.

> > +static int get_vlan_table(struct dsa_switch *ds, u16 vid, u32 *vlan_table)
> > +{
> > +	struct ksz_device *dev = ds->priv;
> > +	u8 data;
> > +	int timeout = 1000;
> > +
> > +	ksz_write16(dev, REG_SW_VLAN_ENTRY_INDEX__2, vid &
> VLAN_INDEX_M);
> > +	ksz_write8(dev, REG_SW_VLAN_CTRL, VLAN_READ | VLAN_START);
> > +
> > +	/* wait to be cleared */
> > +	data = 0;
> > +	do {
> > +		ksz_read8(dev, REG_SW_VLAN_CTRL, &data);
> > +		if (!(data & VLAN_START))
> > +			break;
> > +		usleep_range(1, 10);
> > +	} while (timeout-- > 0);
> > +
> > +	if (!timeout)
> > +		return -ETIMEDOUT;
> > +
> > +	ksz_read32(dev, REG_SW_VLAN_ENTRY__4, &vlan_table[0]);
> > +	ksz_read32(dev, REG_SW_VLAN_ENTRY_UNTAG__4,
> &vlan_table[1]);
> > +	ksz_read32(dev, REG_SW_VLAN_ENTRY_PORTS__4, &vlan_table[2]);
> > +
> > +	ksz_write8(dev, REG_SW_VLAN_CTRL, 0);
> > +
> > +	return 0;
> > +}
> > +
> > +static int set_vlan_table(struct dsa_switch *ds, u16 vid, u32 *vlan_table)
> > +{
> > +	struct ksz_device *dev = ds->priv;
> > +	u8 data;
> > +	int timeout = 1000;
> > +
> > +	ksz_write32(dev, REG_SW_VLAN_ENTRY__4, vlan_table[0]);
> > +	ksz_write32(dev, REG_SW_VLAN_ENTRY_UNTAG__4, vlan_table[1]);
> > +	ksz_write32(dev, REG_SW_VLAN_ENTRY_PORTS__4, vlan_table[2]);
> > +
> > +	ksz_write16(dev, REG_SW_VLAN_ENTRY_INDEX__2, vid &
> VLAN_INDEX_M);
> > +	ksz_write8(dev, REG_SW_VLAN_CTRL, VLAN_START | VLAN_WRITE);
> > +
> > +	do {
> > +		ksz_read8(dev, REG_SW_VLAN_CTRL, &data);
> > +		if (!(data & VLAN_START))
> > +			break;
> > +		usleep_range(1, 10);
> > +	} while (timeout-- > 0);
> > +
> > +	if (!timeout)
> > +		return -ETIMEDOUT;
> > +
> > +	ksz_write8(dev, REG_SW_VLAN_CTRL, 0);
> > +
> > +	mutex_lock(&dev->vlancache_mutex);
> 
> Humm. I think this is wrong. Shouldn't you hold the mutex while you
> change the hardware as well as the cache. Otherwise there is a risk
> your cache could be different to the hardware when you get a race
> between two threads?
Thanks for pointing this out.
Rather than two separate mutex (H/W and vlancache), will put one HW access mutex
around get_vlan_table and set_vlan_table to cover vlancache access too. Even though
little bit overhead. How do you think?

- Woojung