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Message-ID: <20250225112043.419189-2-maxime.chevallier@bootlin.com>
Date: Tue, 25 Feb 2025 12:20:39 +0100
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: davem@...emloft.net,
Andrew Lunn <andrew@...n.ch>,
Jakub Kicinski <kuba@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Paolo Abeni <pabeni@...hat.com>,
Russell King <linux@...linux.org.uk>,
Heiner Kallweit <hkallweit1@...il.com>
Cc: Maxime Chevallier <maxime.chevallier@...tlin.com>,
netdev@...r.kernel.org,
linux-kernel@...r.kernel.org,
thomas.petazzoni@...tlin.com,
Florian Fainelli <f.fainelli@...il.com>,
Köry Maincent <kory.maincent@...tlin.com>,
Simon Horman <horms@...nel.org>,
Romain Gantois <romain.gantois@...tlin.com>,
Antoine Tenart <atenart@...nel.org>,
Marek Behún <kabel@...nel.org>,
Sean Anderson <sean.anderson@...ux.dev>,
Bjørn Mork <bjorn@...k.no>
Subject: [PATCH net-next v2 1/2] net: phy: sfp: Add support for SMBus module access
The SFP module's eeprom and internals are accessible through an i2c bus.
However, all the i2c transfers that are performed are SMBus-style
transfers for read and write operations.
It is possible that the SFP might be connected to an SMBus-only
controller, such as the one found in some PHY devices in the VSC85xx
family.
Introduce a set of sfp read/write ops that are going to be used if the
i2c bus is only capable of doing smbus byte accesses.
As Single-byte SMBus transaction go against SFF-8472 and breaks the
atomicity for diagnostics data access, hwmon is disabled in the case
of SMBus access.
Moreover, as this may cause other instabilities, print a warning at
probe time to indicate that the setup may be unreliable because of the
hardware design.
Tested-by: Sean Anderson <sean.anderson@...ux.dev>
Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.com>
---
V2: - Added Sean's tested-by
- Added a warning indicating that operations won't be reliable, from
Russell and Andrew's reviews
- Also added a flag saying we're under a single-byte-access bus, to
both print the warning and disable hwmon.
drivers/net/phy/sfp.c | 79 +++++++++++++++++++++++++++++++++++++++----
1 file changed, 73 insertions(+), 6 deletions(-)
diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 9369f5297769..6e9d3d95eb95 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -282,6 +282,7 @@ struct sfp {
unsigned int rs_state_mask;
bool have_a2;
+ bool single_byte_access;
const struct sfp_quirk *quirk;
@@ -690,14 +691,70 @@ static int sfp_i2c_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
return ret == ARRAY_SIZE(msgs) ? len : 0;
}
-static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
+static int sfp_smbus_read(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+ size_t len)
{
- if (!i2c_check_functionality(i2c, I2C_FUNC_I2C))
- return -EINVAL;
+ u8 bus_addr = a2 ? 0x51 : 0x50;
+ union i2c_smbus_data smbus_data;
+ u8 *data = buf;
+ int ret;
+
+ while (len) {
+ ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+ I2C_SMBUS_READ, dev_addr,
+ I2C_SMBUS_BYTE_DATA, &smbus_data);
+ if (ret < 0)
+ return ret;
+
+ *data = smbus_data.byte;
+
+ len--;
+ data++;
+ dev_addr++;
+ }
+
+ return data - (u8 *)buf;
+}
+
+static int sfp_smbus_write(struct sfp *sfp, bool a2, u8 dev_addr, void *buf,
+ size_t len)
+{
+ u8 bus_addr = a2 ? 0x51 : 0x50;
+ union i2c_smbus_data smbus_data;
+ u8 *data = buf;
+ int ret;
+ while (len) {
+ smbus_data.byte = *data;
+ ret = i2c_smbus_xfer(sfp->i2c, bus_addr, 0,
+ I2C_SMBUS_WRITE, dev_addr,
+ I2C_SMBUS_BYTE_DATA, &smbus_data);
+ if (ret)
+ return ret;
+
+ len--;
+ data++;
+ dev_addr++;
+ }
+
+ return 0;
+}
+
+static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
+{
sfp->i2c = i2c;
- sfp->read = sfp_i2c_read;
- sfp->write = sfp_i2c_write;
+
+ if (i2c_check_functionality(i2c, I2C_FUNC_I2C)) {
+ sfp->read = sfp_i2c_read;
+ sfp->write = sfp_i2c_write;
+ } else if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA)) {
+ sfp->read = sfp_smbus_read;
+ sfp->write = sfp_smbus_write;
+ sfp->single_byte_access = true;
+ } else {
+ sfp->i2c = NULL;
+ return -EINVAL;
+ }
return 0;
}
@@ -1628,7 +1685,8 @@ static void sfp_hwmon_probe(struct work_struct *work)
static int sfp_hwmon_insert(struct sfp *sfp)
{
- if (sfp->have_a2 && sfp->id.ext.diagmon & SFP_DIAGMON_DDM) {
+ if (sfp->have_a2 && sfp->id.ext.diagmon & SFP_DIAGMON_DDM &&
+ !sfp->single_byte_access) {
mod_delayed_work(system_wq, &sfp->hwmon_probe, 1);
sfp->hwmon_tries = R_PROBE_RETRY_SLOW;
}
@@ -3114,6 +3172,15 @@ static int sfp_probe(struct platform_device *pdev)
if (!sfp->sfp_bus)
return -ENOMEM;
+ if (sfp->single_byte_access)
+ dev_warn(sfp->dev,
+ "Please note:\n"
+ "This SFP cage is accessed via an SMBus only capable of single byte\n"
+ "transactions. Some features are disabled, other may be unreliable or\n"
+ "sporadically fail. Use with caution. There is nothing that the kernel\n"
+ "or community can do to fix it, the kernel will try best efforts. Please\n"
+ "verify any problems on hardware that supports multi-byte I2C transactions.\n");
+
sfp_debugfs_init(sfp);
return 0;
--
2.48.1
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