From: Greg Patrick Date: Thu, 11 Jun 2026 17:53:41 +0000 (+0000) Subject: net: phy: sfp: detect presence via I2C when no MOD_DEF0 GPIO X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=8ac44d24c3a148c4177bd3ad790c377279f4674f;p=thirdparty%2Fkernel%2Flinux.git net: phy: sfp: detect presence via I2C when no MOD_DEF0 GPIO An SFP cage (compatible "sff,sfp") whose MOD_DEF0 signal is not wired to a GPIO currently falls back to sff_gpio_get_state(), which unconditionally reports the module as present. An empty cage therefore fails its probe and is parked in SFP_MOD_ERROR forever; because SFP_F_PRESENT never deasserts there is no REMOVE event to recover the state machine, so a module inserted after boot is never detected, and empty cages spam -EIO at boot. This affects boards that route none of the cage presence signal to a software-readable input. On the NicGiga S100-0800S-M (RTL9303, 8x SFP+) the cage I2C bus is the switch's SMBus master; TX_DISABLE is driven via a PCA9534 I/O expander, but no MOD_ABS/MOD_DEF0 line reaches a readable GPIO (the RTL9303 gpio0 lines read stuck-low, the single PCA9534 is fully consumed by TX_DISABLE, and there is no RTL8231). The Horaco ZX-SW82TS-L2P (RTL9302D, 2x SFP+) is independently affected in the same way. For such an SFP cage, derive presence from a throttled single-byte I2C read of the module EEPROM instead: a successful read asserts SFP_F_PRESENT, R_PROBE_ABSENT consecutive failures clear it (to ride out a transient error on a live module). The existing poll then emits SFP_E_INSERT / SFP_E_REMOVE normally, giving working hot-plug and silencing the boot-time -EIO spam on empty cages. Presence is re-probed every T_PROBE_PRESENT, so insertion is detected within that interval and removal within T_PROBE_PRESENT * R_PROBE_ABSENT. A soldered-down module (compatible "sff,sff") has no presence signal and is genuinely always present, so it continues to use sff_gpio_get_state(); the new path is gated on the cage type advertising SFP_F_PRESENT. Signed-off-by: Greg Patrick Tested-by: Manuel Stocker Reviewed-by: Maxime Chevallier Tested-by: Maxime Chevallier Link: https://patch.msgid.link/20260611175341.2223184-1-gregspatrick@hotmail.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c index 18f2584dbe7bd..caeda3291b301 100644 --- a/drivers/net/phy/sfp.c +++ b/drivers/net/phy/sfp.c @@ -206,6 +206,16 @@ static const enum gpiod_flags gpio_flags[] = { #define T_PROBE_RETRY_SLOW msecs_to_jiffies(5000) #define R_PROBE_RETRY_SLOW 12 +/* Polling interval and consecutive-failure threshold for the I2C presence + * probe used on boards without a MOD_DEF0 GPIO (see sfp_i2c_get_state()). + * A single successful read asserts presence immediately; R_PROBE_ABSENT + * consecutive failures are required to declare a live module removed, to ride + * out a transient I2C error. Insertion is thus detected within + * T_PROBE_PRESENT and removal within T_PROBE_PRESENT * R_PROBE_ABSENT. + */ +#define T_PROBE_PRESENT msecs_to_jiffies(500) +#define R_PROBE_ABSENT 3 + /* SFP modules appear to always have their PHY configured for bus address * 0x56 (which with mdio-i2c, translates to a PHY address of 22). * RollBall SFPs access phy via SFP Enhanced Digital Diagnostic Interface @@ -249,6 +259,13 @@ struct sfp { bool need_poll; + /* I2C-probed presence, for boards without a MOD_DEF0 GPIO. + * Access rules: st_mutex held (updated from the poll/state machine). + */ + bool i2c_present; + u8 i2c_present_nak; + unsigned long i2c_present_next; + /* Access rules: * state_hw_drive: st_mutex held * state_hw_mask: st_mutex held @@ -864,6 +881,45 @@ static int sfp_read(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len) return sfp->read(sfp, a2, addr, buf, len); } +/* Probe whether a module is physically present by attempting a single-byte + * I2C read of the EEPROM identifier (an empty cage NAKs). Used as the presence + * source on boards that do not wire MOD_DEF0 to a GPIO. + */ +static bool sfp_module_present_i2c(struct sfp *sfp) +{ + u8 id; + + return sfp_read(sfp, false, SFP_PHYS_ID, &id, sizeof(id)) == sizeof(id); +} + +/* get_state variant for boards without a MOD_DEF0 GPIO. Instead of assuming + * the module is always present, derive SFP_F_PRESENT from a throttled I2C + * probe so that hot-insertion and removal are detected. A single ACK asserts + * presence; R_PROBE_ABSENT consecutive failures clear it, to ride out a + * transient I2C error on a live module. + */ +static unsigned int sfp_i2c_get_state(struct sfp *sfp) +{ + unsigned int state = sfp_gpio_get_state(sfp); + + if (time_after_eq(jiffies, sfp->i2c_present_next)) { + if (sfp_module_present_i2c(sfp)) { + sfp->i2c_present = true; + sfp->i2c_present_nak = 0; + } else if (sfp->i2c_present && + ++sfp->i2c_present_nak >= R_PROBE_ABSENT) { + sfp->i2c_present = false; + sfp->i2c_present_nak = 0; + } + sfp->i2c_present_next = jiffies + T_PROBE_PRESENT; + } + + if (sfp->i2c_present) + state |= SFP_F_PRESENT; + + return state; +} + static int sfp_write(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len) { return sfp->write(sfp, a2, addr, buf, len); @@ -3169,9 +3225,30 @@ static int sfp_probe(struct platform_device *pdev) sfp->get_state = sfp_gpio_get_state; sfp->set_state = sfp_gpio_set_state; - /* Modules that have no detect signal are always present */ - if (!(sfp->gpio[GPIO_MODDEF0])) - sfp->get_state = sff_gpio_get_state; + /* An SFP cage with no MOD_DEF0 GPIO has no hardware presence signal. + * Assuming the module is always present traps an empty cage in + * MOD_ERROR and never detects hot-insertion, so derive presence from a + * throttled I2C probe and poll for changes instead. sfp_i2c_configure() + * has already set i2c_max_block_size; seed i2c_block_size so the + * presence read does not issue a zero-length transfer before the first + * EEPROM read. Seed i2c_present_next to jiffies so the first probe + * happens immediately (a zero value would be in the past relative to + * the negative INITIAL_JIFFIES at boot and delay detection). + * + * A soldered-down module (sff,sff) has no presence signal and is + * genuinely always present, so it keeps the always-present behaviour; + * the I2C probe is gated on the cage type advertising SFP_F_PRESENT. + */ + if (!sfp->gpio[GPIO_MODDEF0]) { + if (sff->gpios & SFP_F_PRESENT) { + sfp->get_state = sfp_i2c_get_state; + sfp->i2c_block_size = sfp->i2c_max_block_size; + sfp->i2c_present_next = jiffies; + sfp->need_poll = true; + } else { + sfp->get_state = sff_gpio_get_state; + } + } device_property_read_u32(&pdev->dev, "maximum-power-milliwatt", &sfp->max_power_mW);