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net: dsa: microchip: Set SPI as bus interface during reset for KSZ8463

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At reset, the KSZ8463 uses a strap-based configuration to set SPI as
bus interface. SPI is the only bus supported by the driver. If the
required pull-ups/pull-downs are missing (by mistake or by design to
save power) the pins may float and the configuration can go wrong
preventing any communication with the switch.

Introduce a ksz8463_configure_straps_spi() function called during the
device reset. It relies on the 'straps-rxd-gpios' OF property and the
'reset' pinmux configuration to enforce SPI as bus interface.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Bastien Curutchet (Schneider Electric) <bastien.curutchet@bootlin.com>
Link: https://patch.msgid.link/20250918-ksz-strap-pins-v3-3-16662e881728@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Bastien Curutchet
2025-09-18 10:33:52 +02:00
committed by Jakub Kicinski
parent e469b87e0f
commit a0b977a3d1
1 changed files with 45 additions and 0 deletions
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45
drivers/net/dsa/microchip/ksz_common.c
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@@ -23,6 +23,7 @@
#include <linux/of_mdio.h>
#include <linux/of_net.h>
#include <linux/micrel_phy.h>
#include <linux/pinctrl/consumer.h>
#include <net/dsa.h>
#include <net/ieee8021q.h>
#include <net/pkt_cls.h>
@@ -5345,6 +5346,38 @@ static int ksz_parse_drive_strength(struct ksz_device *dev)
return 0;
}
static int ksz8463_configure_straps_spi(struct ksz_device *dev)
{
struct pinctrl *pinctrl;
struct gpio_desc *rxd0;
struct gpio_desc *rxd1;
rxd0 = devm_gpiod_get_index_optional(dev->dev, "straps-rxd", 0, GPIOD_OUT_LOW);
if (IS_ERR(rxd0))
return PTR_ERR(rxd0);
rxd1 = devm_gpiod_get_index_optional(dev->dev, "straps-rxd", 1, GPIOD_OUT_HIGH);
if (IS_ERR(rxd1))
return PTR_ERR(rxd1);
if (!rxd0 && !rxd1)
return 0;
if ((rxd0 && !rxd1) || (rxd1 && !rxd0))
return -EINVAL;
pinctrl = devm_pinctrl_get_select(dev->dev, "reset");
if (IS_ERR(pinctrl))
return PTR_ERR(pinctrl);
return 0;
}
static int ksz8463_release_straps_spi(struct ksz_device *dev)
{
return pinctrl_select_default_state(dev->dev);
}
int ksz_switch_register(struct ksz_device *dev)
{
const struct ksz_chip_data *info;
@@ -5360,10 +5393,22 @@ int ksz_switch_register(struct ksz_device *dev)
return PTR_ERR(dev->reset_gpio);
if (dev->reset_gpio) {
if (of_device_is_compatible(dev->dev->of_node, "microchip,ksz8463")) {
ret = ksz8463_configure_straps_spi(dev);
if (ret)
return ret;
}
gpiod_set_value_cansleep(dev->reset_gpio, 1);
usleep_range(10000, 12000);
gpiod_set_value_cansleep(dev->reset_gpio, 0);
msleep(100);
if (of_device_is_compatible(dev->dev->of_node, "microchip,ksz8463")) {
ret = ksz8463_release_straps_spi(dev);
if (ret)
return ret;
}
}
mutex_init(&dev->dev_mutex);