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linux/drivers/net/dsa/b53/b53_spi.c
Vladimir Oltean 0650bf52b3 net: dsa: be compatible with masters which unregister on shutdown 
Lino reports that on his system with bcmgenet as DSA master and KSZ9897
as a switch, rebooting or shutting down never works properly.

What does the bcmgenet driver have special to trigger this, that other
DSA masters do not? It has an implementation of ->shutdown which simply
calls its ->remove implementation. Otherwise said, it unregisters its
network interface on shutdown.

This message can be seen in a loop, and it hangs the reboot process there:

unregister_netdevice: waiting for eth0 to become free. Usage count = 3

So why 3?

A usage count of 1 is normal for a registered network interface, and any
virtual interface which links itself as an upper of that will increment
it via dev_hold. In the case of DSA, this is the call path:

dsa_slave_create
-> netdev_upper_dev_link
   -> __netdev_upper_dev_link
      -> __netdev_adjacent_dev_insert
         -> dev_hold

So a DSA switch with 3 interfaces will result in a usage count elevated
by two, and netdev_wait_allrefs will wait until they have gone away.

Other stacked interfaces, like VLAN, watch NETDEV_UNREGISTER events and
delete themselves, but DSA cannot just vanish and go poof, at most it
can unbind itself from the switch devices, but that must happen strictly
earlier compared to when the DSA master unregisters its net_device, so
reacting on the NETDEV_UNREGISTER event is way too late.

It seems that it is a pretty established pattern to have a driver's
->shutdown hook redirect to its ->remove hook, so the same code is
executed regardless of whether the driver is unbound from the device, or
the system is just shutting down. As Florian puts it, it is quite a big
hammer for bcmgenet to unregister its net_device during shutdown, but
having a common code path with the driver unbind helps ensure it is well
tested.

So DSA, for better or for worse, has to live with that and engage in an
arms race of implementing the ->shutdown hook too, from all individual
drivers, and do something sane when paired with masters that unregister
their net_device there. The only sane thing to do, of course, is to
unlink from the master.

However, complications arise really quickly.

The pattern of redirecting ->shutdown to ->remove is not unique to
bcmgenet or even to net_device drivers. In fact, SPI controllers do it
too (see dspi_shutdown -> dspi_remove), and presumably, I2C controllers
and MDIO controllers do it too (this is something I have not researched
too deeply, but even if this is not the case today, it is certainly
plausible to happen in the future, and must be taken into consideration).

Since DSA switches might be SPI devices, I2C devices, MDIO devices, the
insane implication is that for the exact same DSA switch device, we
might have both ->shutdown and ->remove getting called.

So we need to do something with that insane environment. The pattern
I've come up with is "if this, then not that", so if either ->shutdown
or ->remove gets called, we set the device's drvdata to NULL, and in the
other hook, we check whether the drvdata is NULL and just do nothing.
This is probably not necessary for platform devices, just for devices on
buses, but I would really insist for consistency among drivers, because
when code is copy-pasted, it is not always copy-pasted from the best
sources.

So depending on whether the DSA switch's ->remove or ->shutdown will get
called first, we cannot really guarantee even for the same driver if
rebooting will result in the same code path on all platforms. But
nonetheless, we need to do something minimally reasonable on ->shutdown
too to fix the bug. Of course, the ->remove will do more (a full
teardown of the tree, with all data structures freed, and this is why
the bug was not caught for so long). The new ->shutdown method is kept
separate from dsa_unregister_switch not because we couldn't have
unregistered the switch, but simply in the interest of doing something
quick and to the point.

The big question is: does the DSA switch's ->shutdown get called earlier
than the DSA master's ->shutdown? If not, there is still a risk that we
might still trigger the WARN_ON in unregister_netdevice that says we are
attempting to unregister a net_device which has uppers. That's no good.
Although the reference to the master net_device won't physically go away
even if DSA's ->shutdown comes afterwards, remember we have a dev_hold
on it.

The answer to that question lies in this comment above device_link_add:

 * A side effect of the link creation is re-ordering of dpm_list and the
 * devices_kset list by moving the consumer device and all devices depending
 * on it to the ends of these lists (that does not happen to devices that have
 * not been registered when this function is called).

so the fact that DSA uses device_link_add towards its master is not
exactly for nothing. device_shutdown() walks devices_kset from the back,
so this is our guarantee that DSA's shutdown happens before the master's
shutdown.

Fixes: 2f1e8ea726 ("net: dsa: link interfaces with the DSA master to get rid of lockdep warnings")
Link: https://lore.kernel.org/netdev/20210909095324.12978-1-LinoSanfilippo@gmx.de/
Reported-by: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-09-19 12:08:37 +01:00

367 lines
7.5 KiB
C
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/*
* B53 register access through SPI
*
* Copyright (C) 2011-2013 Jonas Gorski <jogo@openwrt.org>
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <asm/unaligned.h>
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spi/spi.h>
#include <linux/platform_data/b53.h>
#include "b53_priv.h"
#define B53_SPI_DATA 0xf0
#define B53_SPI_STATUS 0xfe
#define B53_SPI_CMD_SPIF BIT(7)
#define B53_SPI_CMD_RACK BIT(5)
#define B53_SPI_CMD_READ 0x00
#define B53_SPI_CMD_WRITE 0x01
#define B53_SPI_CMD_NORMAL 0x60
#define B53_SPI_CMD_FAST 0x10
#define B53_SPI_PAGE_SELECT 0xff
static inline int b53_spi_read_reg(struct spi_device *spi, u8 reg, u8 *val,
unsigned int len)
{
u8 txbuf[2];
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_READ;
txbuf[1] = reg;
return spi_write_then_read(spi, txbuf, 2, val, len);
}
static inline int b53_spi_clear_status(struct spi_device *spi)
{
unsigned int i;
u8 rxbuf;
int ret;
for (i = 0; i < 10; i++) {
ret = b53_spi_read_reg(spi, B53_SPI_STATUS, &rxbuf, 1);
if (ret)
return ret;
if (!(rxbuf & B53_SPI_CMD_SPIF))
break;
mdelay(1);
}
if (i == 10)
return -EIO;
return 0;
}
static inline int b53_spi_set_page(struct spi_device *spi, u8 page)
{
u8 txbuf[3];
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_WRITE;
txbuf[1] = B53_SPI_PAGE_SELECT;
txbuf[2] = page;
return spi_write(spi, txbuf, sizeof(txbuf));
}
static inline int b53_prepare_reg_access(struct spi_device *spi, u8 page)
{
int ret = b53_spi_clear_status(spi);
if (ret)
return ret;
return b53_spi_set_page(spi, page);
}
static int b53_spi_prepare_reg_read(struct spi_device *spi, u8 reg)
{
u8 rxbuf;
int retry_count;
int ret;
ret = b53_spi_read_reg(spi, reg, &rxbuf, 1);
if (ret)
return ret;
for (retry_count = 0; retry_count < 10; retry_count++) {
ret = b53_spi_read_reg(spi, B53_SPI_STATUS, &rxbuf, 1);
if (ret)
return ret;
if (rxbuf & B53_SPI_CMD_RACK)
break;
mdelay(1);
}
if (retry_count == 10)
return -EIO;
return 0;
}
static int b53_spi_read(struct b53_device *dev, u8 page, u8 reg, u8 *data,
unsigned int len)
{
struct spi_device *spi = dev->priv;
int ret;
ret = b53_prepare_reg_access(spi, page);
if (ret)
return ret;
ret = b53_spi_prepare_reg_read(spi, reg);
if (ret)
return ret;
return b53_spi_read_reg(spi, B53_SPI_DATA, data, len);
}
static int b53_spi_read8(struct b53_device *dev, u8 page, u8 reg, u8 *val)
{
return b53_spi_read(dev, page, reg, val, 1);
}
static int b53_spi_read16(struct b53_device *dev, u8 page, u8 reg, u16 *val)
{
__le16 value;
int ret;
ret = b53_spi_read(dev, page, reg, (u8 *)&value, 2);
if (!ret)
*val = le16_to_cpu(value);
return ret;
}
static int b53_spi_read32(struct b53_device *dev, u8 page, u8 reg, u32 *val)
{
__le32 value;
int ret;
ret = b53_spi_read(dev, page, reg, (u8 *)&value, 4);
if (!ret)
*val = le32_to_cpu(value);
return ret;
}
static int b53_spi_read48(struct b53_device *dev, u8 page, u8 reg, u64 *val)
{
__le64 value;
int ret;
*val = 0;
ret = b53_spi_read(dev, page, reg, (u8 *)&value, 6);
if (!ret)
*val = le64_to_cpu(value);
return ret;
}
static int b53_spi_read64(struct b53_device *dev, u8 page, u8 reg, u64 *val)
{
__le64 value;
int ret;
ret = b53_spi_read(dev, page, reg, (u8 *)&value, 8);
if (!ret)
*val = le64_to_cpu(value);
return ret;
}
static int b53_spi_write8(struct b53_device *dev, u8 page, u8 reg, u8 value)
{
struct spi_device *spi = dev->priv;
int ret;
u8 txbuf[3];
ret = b53_prepare_reg_access(spi, page);
if (ret)
return ret;
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_WRITE;
txbuf[1] = reg;
txbuf[2] = value;
return spi_write(spi, txbuf, sizeof(txbuf));
}
static int b53_spi_write16(struct b53_device *dev, u8 page, u8 reg, u16 value)
{
struct spi_device *spi = dev->priv;
int ret;
u8 txbuf[4];
ret = b53_prepare_reg_access(spi, page);
if (ret)
return ret;
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_WRITE;
txbuf[1] = reg;
put_unaligned_le16(value, &txbuf[2]);
return spi_write(spi, txbuf, sizeof(txbuf));
}
static int b53_spi_write32(struct b53_device *dev, u8 page, u8 reg, u32 value)
{
struct spi_device *spi = dev->priv;
int ret;
u8 txbuf[6];
ret = b53_prepare_reg_access(spi, page);
if (ret)
return ret;
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_WRITE;
txbuf[1] = reg;
put_unaligned_le32(value, &txbuf[2]);
return spi_write(spi, txbuf, sizeof(txbuf));
}
static int b53_spi_write48(struct b53_device *dev, u8 page, u8 reg, u64 value)
{
struct spi_device *spi = dev->priv;
int ret;
u8 txbuf[10];
ret = b53_prepare_reg_access(spi, page);
if (ret)
return ret;
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_WRITE;
txbuf[1] = reg;
put_unaligned_le64(value, &txbuf[2]);
return spi_write(spi, txbuf, sizeof(txbuf) - 2);
}
static int b53_spi_write64(struct b53_device *dev, u8 page, u8 reg, u64 value)
{
struct spi_device *spi = dev->priv;
int ret;
u8 txbuf[10];
ret = b53_prepare_reg_access(spi, page);
if (ret)
return ret;
txbuf[0] = B53_SPI_CMD_NORMAL | B53_SPI_CMD_WRITE;
txbuf[1] = reg;
put_unaligned_le64(value, &txbuf[2]);
return spi_write(spi, txbuf, sizeof(txbuf));
}
static const struct b53_io_ops b53_spi_ops = {
.read8 = b53_spi_read8,
.read16 = b53_spi_read16,
.read32 = b53_spi_read32,
.read48 = b53_spi_read48,
.read64 = b53_spi_read64,
.write8 = b53_spi_write8,
.write16 = b53_spi_write16,
.write32 = b53_spi_write32,
.write48 = b53_spi_write48,
.write64 = b53_spi_write64,
};
static int b53_spi_probe(struct spi_device *spi)
{
struct b53_device *dev;
int ret;
dev = b53_switch_alloc(&spi->dev, &b53_spi_ops, spi);
if (!dev)
return -ENOMEM;
if (spi->dev.platform_data)
dev->pdata = spi->dev.platform_data;
ret = b53_switch_register(dev);
if (ret)
return ret;
spi_set_drvdata(spi, dev);
return 0;
}
static int b53_spi_remove(struct spi_device *spi)
{
struct b53_device *dev = spi_get_drvdata(spi);
if (dev)
b53_switch_remove(dev);
spi_set_drvdata(spi, NULL);
return 0;
}
static void b53_spi_shutdown(struct spi_device *spi)
{
struct b53_device *dev = spi_get_drvdata(spi);
if (dev)
b53_switch_shutdown(dev);
spi_set_drvdata(spi, NULL);
}
static const struct of_device_id b53_spi_of_match[] = {
{ .compatible = "brcm,bcm5325" },
{ .compatible = "brcm,bcm5365" },
{ .compatible = "brcm,bcm5395" },
{ .compatible = "brcm,bcm5397" },
{ .compatible = "brcm,bcm5398" },
{ .compatible = "brcm,bcm53115" },
{ .compatible = "brcm,bcm53125" },
{ .compatible = "brcm,bcm53128" },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, b53_spi_of_match);
static struct spi_driver b53_spi_driver = {
.driver = {
.name = "b53-switch",
.of_match_table = b53_spi_of_match,
},
.probe = b53_spi_probe,
.remove = b53_spi_remove,
.shutdown = b53_spi_shutdown,
};
module_spi_driver(b53_spi_driver);
MODULE_AUTHOR("Jonas Gorski <jogo@openwrt.org>");
MODULE_DESCRIPTION("B53 SPI access driver");
MODULE_LICENSE("Dual BSD/GPL");
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