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[2003:ea:8bf1:e200:7597:929b:df9d:5281]) by smtp.googlemail.com with ESMTPSA id a184sm4140791wmh.37.2019.02.27.15.48.53 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Feb 2019 15:48:54 -0800 (PST) Subject: Re: [PATCH net] net: dsa: mv88e6xxx: prevent interrupt storm caused by mv88e6390x_port_set_cmode To: Vivien Didelot Cc: Andrew Lunn , Florian Fainelli , David Miller , "netdev@vger.kernel.org" References: <864ac062-51cb-ec9e-388b-b74a62eb6e6a@gmail.com> <20190227184040.GB23759@t480s.localdomain> From: Heiner Kallweit Message-ID: <63f9bc69-ae1d-bb24-1517-8f5de661dc54@gmail.com> Date: Thu, 28 Feb 2019 00:48:47 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.1 MIME-Version: 1.0 In-Reply-To: <20190227184040.GB23759@t480s.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 28.02.2019 00:40, Vivien Didelot wrote: > Hi Heiner, > > On Wed, 27 Feb 2019 20:55:22 +0100, Heiner Kallweit wrote: >> When debugging another issue I faced an interrupt storm in this >> driver (88E6390, port 9 in SGMII mode), consisting of alternating >> link-up / link-down interrupts. Analysis showed that the driver >> wanted to set a cmode that was set already. But so far >> mv88e6390x_port_set_cmode() doesn't check this and powers down >> SERDES, what causes the link to break, and eventually results in >> the described interrupt storm. >> >> Fix this by checking whether the cmode actually changes. We want >> that the very first call to mv88e6390x_port_set_cmode() always >> configures the registers, therefore initialize port.cmode with >> a value that is different from any supported cmode value. >> >> Fixes: 364e9d7776a3 ("net: dsa: mv88e6xxx: Power on/off SERDES on cmode change") >> Signed-off-by: Heiner Kallweit >> --- >> drivers/net/dsa/mv88e6xxx/chip.c | 4 ++++ >> drivers/net/dsa/mv88e6xxx/port.c | 4 ++++ >> drivers/net/dsa/mv88e6xxx/port.h | 1 + >> 3 files changed, 9 insertions(+) >> >> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c >> index 32e7af5ca..d4edb61e8 100644 >> --- a/drivers/net/dsa/mv88e6xxx/chip.c >> +++ b/drivers/net/dsa/mv88e6xxx/chip.c >> @@ -4568,6 +4568,7 @@ static int mv88e6xxx_detect(struct mv88e6xxx_chip *chip) >> static struct mv88e6xxx_chip *mv88e6xxx_alloc_chip(struct device *dev) >> { >> struct mv88e6xxx_chip *chip; >> + int i; >> >> chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL); >> if (!chip) >> @@ -4578,6 +4579,9 @@ static struct mv88e6xxx_chip *mv88e6xxx_alloc_chip(struct device *dev) >> mutex_init(&chip->reg_lock); >> INIT_LIST_HEAD(&chip->mdios); >> >> + for (i = 0; i < ARRAY_SIZE(chip->ports); i++) > > mv88e6xxx_num_ports(chip) > OK >> + chip->ports[i].cmode = MV88E6XXX_PORT_STS_CMODE_INVALID; >> + >> return chip; >> } >> >> diff --git a/drivers/net/dsa/mv88e6xxx/port.c b/drivers/net/dsa/mv88e6xxx/port.c >> index ebd26b6a9..70b7a1463 100644 >> --- a/drivers/net/dsa/mv88e6xxx/port.c >> +++ b/drivers/net/dsa/mv88e6xxx/port.c >> @@ -398,6 +398,10 @@ int mv88e6390x_port_set_cmode(struct mv88e6xxx_chip *chip, int port, >> cmode = 0; >> } >> >> + /* cmode doesn't change, nothing to do for us */ >> + if (cmode == chip->ports[port].cmode) >> + return 0; >> + >> lane = mv88e6390x_serdes_get_lane(chip, port); >> if (lane < 0) >> return lane; >> diff --git a/drivers/net/dsa/mv88e6xxx/port.h b/drivers/net/dsa/mv88e6xxx/port.h >> index e583641de..4aadf321e 100644 >> --- a/drivers/net/dsa/mv88e6xxx/port.h >> +++ b/drivers/net/dsa/mv88e6xxx/port.h >> @@ -52,6 +52,7 @@ >> #define MV88E6185_PORT_STS_CMODE_1000BASE_X 0x0005 >> #define MV88E6185_PORT_STS_CMODE_PHY 0x0006 >> #define MV88E6185_PORT_STS_CMODE_DISABLED 0x0007 >> +#define MV88E6XXX_PORT_STS_CMODE_INVALID 0xff > > Is this 0xff a mask value from the Port Status register? If so please > the 0x1234 format like above, to make this mask value obvious. > No, it's not a mask. I couldn't use 0 for "invalid" because 0 is used otherwise, so I went with 0xff. All these STS_CMODE values are also stored in mv88e6xxx_port.cmode that has type u8. Therefore I decided to write it as an 8 bit value. >> >> /* Offset 0x01: MAC (or PCS or Physical) Control Register */ >> #define MV88E6XXX_PORT_MAC_CTL 0x01 > > > Thanks, > > Vivien > Heiner