Re: [PATCH 5.15 291/917] net: dsa: lantiq_gswip: serialize access to the PCE table

Vladimir Oltean
2021-11-16T00:14:06Z

On Mon, Nov 15, 2021 at 05:56:26PM +0100, Greg Kroah-Hartman wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
>
> [ Upstream commit 49753a75b9a32de4c0393bb8d1e51ea223fda8e4 ]
>
> Looking at the code, the GSWIP switch appears to hold bridging service
> structures (VLANs, FDBs, forwarding rules) in PCE table entries.
> Hardware access to the PCE table is non-atomic, and is comprised of
> several register reads and writes.
>
> These accesses are currently serialized by the rtnl_lock, but DSA is
> changing its driver API and that lock will no longer be held when
> calling ->port_fdb_add() and ->port_fdb_del().
>
> So this driver needs to serialize the access to the PCE table using its
> own locking scheme. This patch adds that.
>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
> Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> drivers/net/dsa/lantiq_gswip.c | 28 +++++++++++++++++++++++-----
> 1 file changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/dsa/lantiq_gswip.c b/drivers/net/dsa/lantiq_gswip.c
> index dbd4486a173ff..1a96df70d1e85 100644
> --- a/drivers/net/dsa/lantiq_gswip.c
> +++ b/drivers/net/dsa/lantiq_gswip.c
> @@ -276,6 +276,7 @@ struct gswip_priv {
> int num_gphy_fw;
> struct gswip_gphy_fw *gphy_fw;
> u32 port_vlan_filter;
> + struct mutex pce_table_lock;
> };
>
> struct gswip_pce_table_entry {
> @@ -523,10 +524,14 @@ static int gswip_pce_table_entry_read(struct gswip_priv *priv,
> u16 addr_mode = tbl->key_mode ? GSWIP_PCE_TBL_CTRL_OPMOD_KSRD :
> GSWIP_PCE_TBL_CTRL_OPMOD_ADRD;
>
> + mutex_lock(&priv->pce_table_lock);
> +
> err = gswip_switch_r_timeout(priv, GSWIP_PCE_TBL_CTRL,
> GSWIP_PCE_TBL_CTRL_BAS);
> - if (err)
> + if (err) {
> + mutex_unlock(&priv->pce_table_lock);
> return err;
> + }
>
> gswip_switch_w(priv, tbl->index, GSWIP_PCE_TBL_ADDR);
> gswip_switch_mask(priv, GSWIP_PCE_TBL_CTRL_ADDR_MASK |
> @@ -536,8 +541,10 @@ static int gswip_pce_table_entry_read(struct gswip_priv *priv,
>
> err = gswip_switch_r_timeout(priv, GSWIP_PCE_TBL_CTRL,
> GSWIP_PCE_TBL_CTRL_BAS);
> - if (err)
> + if (err) {
> + mutex_unlock(&priv->pce_table_lock);
> return err;
> + }
>
> for (i = 0; i < ARRAY_SIZE(tbl->key); i++)
> tbl->key[i] = gswip_switch_r(priv, GSWIP_PCE_TBL_KEY(i));
> @@ -553,6 +560,8 @@ static int gswip_pce_table_entry_read(struct gswip_priv *priv,
> tbl->valid = !!(crtl & GSWIP_PCE_TBL_CTRL_VLD);
> tbl->gmap = (crtl & GSWIP_PCE_TBL_CTRL_GMAP_MASK) >> 7;
>
> + mutex_unlock(&priv->pce_table_lock);
> +
> return 0;
> }
>
> @@ -565,10 +574,14 @@ static int gswip_pce_table_entry_write(struct gswip_priv *priv,
> u16 addr_mode = tbl->key_mode ? GSWIP_PCE_TBL_CTRL_OPMOD_KSWR :
> GSWIP_PCE_TBL_CTRL_OPMOD_ADWR;
>
> + mutex_lock(&priv->pce_table_lock);
> +
> err = gswip_switch_r_timeout(priv, GSWIP_PCE_TBL_CTRL,
> GSWIP_PCE_TBL_CTRL_BAS);
> - if (err)
> + if (err) {
> + mutex_unlock(&priv->pce_table_lock);
> return err;
> + }
>
> gswip_switch_w(priv, tbl->index, GSWIP_PCE_TBL_ADDR);
> gswip_switch_mask(priv, GSWIP_PCE_TBL_CTRL_ADDR_MASK |
> @@ -600,8 +613,12 @@ static int gswip_pce_table_entry_write(struct gswip_priv *priv,
> crtl |= GSWIP_PCE_TBL_CTRL_BAS;
> gswip_switch_w(priv, crtl, GSWIP_PCE_TBL_CTRL);
>
> - return gswip_switch_r_timeout(priv, GSWIP_PCE_TBL_CTRL,
> - GSWIP_PCE_TBL_CTRL_BAS);
> + err = gswip_switch_r_timeout(priv, GSWIP_PCE_TBL_CTRL,
> + GSWIP_PCE_TBL_CTRL_BAS);
> +
> + mutex_unlock(&priv->pce_table_lock);
> +
> + return err;
> }
>
> /* Add the LAN port into a bridge with the CPU port by
> @@ -2106,6 +2123,7 @@ static int gswip_probe(struct platform_device *pdev)
> priv->ds->priv = priv;
> priv->ds->ops = priv->hw_info->ops;
> priv->dev = dev;
> + mutex_init(&priv->pce_table_lock);
> version = gswip_switch_r(priv, GSWIP_VERSION);
>
> np = dev->of_node;
> --
> 2.33.0
>
>
>

As discussed on the v5.14 backport, this patch can be dropped.