netdev - [PATCH net-next 2/7] net: sfp: check firmware provided max power

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Date:   Fri, 21 Oct 2022 16:09:43 +0100
From:   "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>
To:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Andrew Lunn <andrew@...n.ch>, devicetree@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: [PATCH net-next 2/7] net: sfp: check firmware provided max power

Check that the firmware provided maximum power is at least 1W, which
iis the minimum power level for any SFP module.

Now that we enforce the minimum of 1W, we can exit early from
sfp_module_parse_power() if the module power is 1W or less.

Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
---
 drivers/net/phy/sfp.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index 40c9a64c5e30..f7ad4d5d9041 100644
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -1766,6 +1766,12 @@ static int sfp_module_parse_power(struct sfp *sfp)
 	if (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_HIGH_POWER_LEVEL))
 		power_mW = 2000;
 
+	/* Power level 1 modules (max. 1W) are always supported. */
+	if (power_mW <= 1000) {
+		sfp->module_power_mW = power_mW;
+		return 0;
+	}
+
 	supports_a2 = sfp->id.ext.sff8472_compliance !=
 				SFP_SFF8472_COMPLIANCE_NONE ||
 		      sfp->id.ext.diagmon & SFP_DIAGMON_DDM;
@@ -1789,12 +1795,6 @@ static int sfp_module_parse_power(struct sfp *sfp)
 		}
 	}
 
-	if (power_mW <= 1000) {
-		/* Modules below 1W do not require a power change sequence */
-		sfp->module_power_mW = power_mW;
-		return 0;
-	}
-
 	if (!supports_a2) {
 		/* The module power level is below the host maximum and the
 		 * module appears not to implement bus address 0xa2, so assume
@@ -2729,8 +2729,12 @@ static int sfp_probe(struct platform_device *pdev)
 
 	device_property_read_u32(&pdev->dev, "maximum-power-milliwatt",
 				 &sfp->max_power_mW);
-	if (!sfp->max_power_mW)
+	if (sfp->max_power_mW < 1000) {
+		if (sfp->max_power_mW)
+			dev_warn(sfp->dev,
+				 "Firmware bug: host maximum power should be at least 1W\n");
 		sfp->max_power_mW = 1000;
+	}
 
 	dev_info(sfp->dev, "Host maximum power %u.%uW\n",
 		 sfp->max_power_mW / 1000, (sfp->max_power_mW / 100) % 10);
-- 
2.30.2