linux-kernel - [PATCH v2 7/8] PCI: brcmstb: Make two changes in MDIO register fields

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Message-ID: <20250214173944.47506-8-james.quinlan@broadcom.com>
Date: Fri, 14 Feb 2025 12:39:35 -0500
From: Jim Quinlan <james.quinlan@...adcom.com>
To: linux-pci@...r.kernel.org,
	Nicolas Saenz Julienne <nsaenz@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Cyril Brulebois <kibi@...ian.org>,
	Stanimir Varbanov <svarbanov@...e.de>,
	bcm-kernel-feedback-list@...adcom.com,
	jim2101024@...il.com,
	james.quinlan@...adcom.com
Cc: Florian Fainelli <florian.fainelli@...adcom.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Rob Herring <robh@...nel.org>,
	linux-rpi-kernel@...ts.infradead.org (moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE),
	linux-arm-kernel@...ts.infradead.org (moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE),
	linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v2 7/8] PCI: brcmstb: Make two changes in MDIO register fields

The HW team has decided to "tighten" some field definitions in the MDIO
packet format.  Fortunately these two changes may be made in a backwards
compatible manner.

The CMD field used to be 12 bits and now is one.  This change is backwards
compatible because the field's starting bit position is unchanged and the
only commands we've used have values 0 and 1.

The PORT field's width has been changed from four to five bits.  When
written, the new bit is not contiguous with the other four.  Fortunately,
this change is backwards compatible because we have never used anything
other than 0 for the port field's value.

Signed-off-by: Jim Quinlan <james.quinlan@...adcom.com>
---
 drivers/pci/controller/pcie-brcmstb.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/pcie-brcmstb.c b/drivers/pci/controller/pcie-brcmstb.c
index 923ac1a03f85..cb897d4b2579 100644
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -175,8 +175,9 @@
 #define MDIO_PORT0			0x0
 #define MDIO_DATA_MASK			0x7fffffff
 #define MDIO_PORT_MASK			0xf0000
+#define MDIO_PORT_EXT_MASK		0x200000
 #define MDIO_REGAD_MASK			0xffff
-#define MDIO_CMD_MASK			0xfff00000
+#define MDIO_CMD_MASK			0x00100000
 #define MDIO_CMD_READ			0x1
 #define MDIO_CMD_WRITE			0x0
 #define MDIO_DATA_DONE_MASK		0x80000000
@@ -327,6 +328,7 @@ static u32 brcm_pcie_mdio_form_pkt(int port, int regad, int cmd)
 {
 	u32 pkt = 0;
 
+	pkt |= FIELD_PREP(MDIO_PORT_EXT_MASK, port >> 4);
 	pkt |= FIELD_PREP(MDIO_PORT_MASK, port);
 	pkt |= FIELD_PREP(MDIO_REGAD_MASK, regad);
 	pkt |= FIELD_PREP(MDIO_CMD_MASK, cmd);
-- 
2.43.0