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    SubjectRe: [PATCH 5.15 291/917] net: dsa: lantiq_gswip: serialize access to the PCE table
    On Mon, Nov 15, 2021 at 11:35:47PM +0000, Vladimir Oltean wrote:
    >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.

    Dropped, thanks!

    --
    Thanks,
    Sasha

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