linux-kernel - [PATCH v3 net] net: dsa: microchip: fix wrong register write when masking interrupt

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Date: Fri, 21 Jun 2024 15:34:22 -0700
From: <Tristram.Ha@...rochip.com>
To: Arun Ramadoss <arun.ramadoss@...rochip.com>, Woojung Huh
	<woojung.huh@...rochip.com>, Andrew Lunn <andrew@...n.ch>, Vivien Didelot
	<vivien.didelot@...il.com>, Florian Fainelli <f.fainelli@...il.com>,
	"Vladimir Oltean" <olteanv@...il.com>
CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, <UNGLinuxDriver@...rochip.com>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Tristram Ha
	<tristram.ha@...rochip.com>
Subject: [PATCH v3 net] net: dsa: microchip: fix wrong register write when masking interrupt

From: Tristram Ha <tristram.ha@...rochip.com>

The switch global port interrupt mask, REG_SW_PORT_INT_MASK__4, is
defined as 0x001C in ksz9477_reg.h.  The designers used 32-bit value in
anticipation for increase of port count in future product but currently
the maximum port count is 7 and the effective value is 0x7F in register
0x001F.  Each port has its own interrupt mask and is defined as 0x#01F.
It uses only 4 bits for different interrupts.

The developer who implemented the current interrupt mechanism in the
switch driver noticed there are similarities between the mechanism to
mask port interrupts in global interrupt and individual interrupts in
each port and so used the same code to handle these interrupts.  He
updated the code to use the new macro REG_SW_PORT_INT_MASK__1 which is
defined as 0x1F in ksz_common.h but he forgot to update the 32-bit write
to 8-bit as now the mask registers are 0x1F and 0x#01F.

In addition all KSZ switches other than the KSZ9897/KSZ9893 and LAN937X
families use only 8-bit access and so this common code will eventually
be changed to accommodate them.

Fixes: e1add7dd6183 ("net: dsa: microchip: use common irq routines for girq and pirq")
Signed-off-by: Tristram Ha <tristram.ha@...rochip.com>
---
v3
 - bump the number for third submission
 - provide the full explanation of modifying the code

v1
 - clarify the reason to change the code

 drivers/net/dsa/microchip/ksz_common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index 1e0085cd9a9a..3ad0879b00cd 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -2185,7 +2185,7 @@ static void ksz_irq_bus_sync_unlock(struct irq_data *d)
 	struct ksz_device *dev = kirq->dev;
 	int ret;

-	ret = ksz_write32(dev, kirq->reg_mask, kirq->masked);
+	ret = ksz_write8(dev, kirq->reg_mask, kirq->masked);
 	if (ret)
 		dev_err(dev->dev, "failed to change IRQ mask\n");

-- 
2.34.1