[PATCH stable 5.16+ 0/3] backported Realtek DSA driver fixes for 5.16 and 5.17

[PATCH stable 5.16+ 0/3] backported Realtek DSA driver fixes for 5.16 and 5.17

[Alvin Šipraga]

From: Alvin Šipraga <alsi@bang-olufsen.dk>

These fixes can be applied to both 5.16 and 5.17 - the subtree of
drivers/net/dsa/realtek is identical save for a few unrelated places.

The main backporting effort was to remove some parts of the patches
which touched the newly introduced MDIO interface, which was introduced
in the 5.18 development cycle, and to work around a mass-rename of a
single variable (smi -> priv). Regrettably this rename will make future
stable backports equally tedious and hard to automate.

Please let me know if you would like me to send the series again for
5.17.

Thanks!


Alvin Šipraga (3):
  net: dsa: realtek: allow subdrivers to externally lock regmap
  net: dsa: realtek: rtl8365mb: serialize indirect PHY register access
  net: dsa: realtek: make interface drivers depend on OF

 drivers/net/dsa/realtek/Kconfig            |  1 +
 drivers/net/dsa/realtek/realtek-smi-core.c | 48 +++++++++++++++++--
 drivers/net/dsa/realtek/realtek-smi-core.h |  2 +
 drivers/net/dsa/realtek/rtl8365mb.c        | 54 +++++++++++++---------
 4 files changed, 81 insertions(+), 24 deletions(-)

-- 
2.35.1

[PATCH stable 5.16+ 1/3] net: dsa: realtek: allow subdrivers to externally lock regmap

[Alvin Šipraga]

From: Alvin Šipraga <alsi@bang-olufsen.dk>

[ Upstream commit 907e772f6f6debb610ea28298ab57b31019a4edb ]

Currently there is no way for Realtek DSA subdrivers to serialize
consecutive regmap accesses. In preparation for a bugfix relating to
indirect PHY register access - which involves a series of regmap
reads and writes - add a facility for subdrivers to serialize their
regmap access.

Specifically, a mutex is added to the driver private data structure and
the standard regmap is initialized with custom lock/unlock ops which use
this mutex. Then, a "nolock" variant of the regmap is added, which is
functionally equivalent to the existing regmap except that regmap
locking is disabled. Functions that wish to serialize a sequence of
regmap accesses may then lock the newly introduced driver-owned mutex
before using the nolock regmap.

Doing things this way means that subdriver code that doesn't care about
serialized register access - i.e. the vast majority of code - needn't
worry about synchronizing register access with an external lock: it can
just continue to use the original regmap.

Another advantage of this design is that, while regmaps with locking
disabled do not expose a debugfs interface for obvious reasons, there
still exists the original regmap which does expose this interface. This
interface remains safe to use even combined with driver codepaths that
use the nolock regmap, because said codepaths will use the same mutex
to synchronize access.

With respect to disadvantages, it can be argued that having
near-duplicate regmaps is confusing. However, the naming is rather
explicit, and examples will abound.

Finally, while we are at it, rename realtek_smi_mdio_regmap_config to
realtek_smi_regmap_config. This makes it consistent with the naming
realtek_mdio_regmap_config in realtek-mdio.c.

Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[alsi: backport to 5.16: s/priv/smi/g and remove realtek-mdio changes]
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
---
 drivers/net/dsa/realtek/realtek-smi-core.c | 48 ++++++++++++++++++++--
 drivers/net/dsa/realtek/realtek-smi-core.h |  2 +
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/drivers/net/dsa/realtek/realtek-smi-core.c b/drivers/net/dsa/realtek/realtek-smi-core.c
index c66ebd0ee217..129ddee41928 100644
--- a/drivers/net/dsa/realtek/realtek-smi-core.c
+++ b/drivers/net/dsa/realtek/realtek-smi-core.c
@@ -315,7 +315,21 @@ static int realtek_smi_read(void *ctx, u32 reg, u32 *val)
 	return realtek_smi_read_reg(smi, reg, val);
 }
 
-static const struct regmap_config realtek_smi_mdio_regmap_config = {
+static void realtek_smi_lock(void *ctx)
+{
+	struct realtek_smi *smi = ctx;
+
+	mutex_lock(&smi->map_lock);
+}
+
+static void realtek_smi_unlock(void *ctx)
+{
+	struct realtek_smi *smi = ctx;
+
+	mutex_unlock(&smi->map_lock);
+}
+
+static const struct regmap_config realtek_smi_regmap_config = {
 	.reg_bits = 10, /* A4..A0 R4..R0 */
 	.val_bits = 16,
 	.reg_stride = 1,
@@ -325,6 +339,21 @@ static const struct regmap_config realtek_smi_mdio_regmap_config = {
 	.reg_read = realtek_smi_read,
 	.reg_write = realtek_smi_write,
 	.cache_type = REGCACHE_NONE,
+	.lock = realtek_smi_lock,
+	.unlock = realtek_smi_unlock,
+};
+
+static const struct regmap_config realtek_smi_nolock_regmap_config = {
+	.reg_bits = 10, /* A4..A0 R4..R0 */
+	.val_bits = 16,
+	.reg_stride = 1,
+	/* PHY regs are at 0x8000 */
+	.max_register = 0xffff,
+	.reg_format_endian = REGMAP_ENDIAN_BIG,
+	.reg_read = realtek_smi_read,
+	.reg_write = realtek_smi_write,
+	.cache_type = REGCACHE_NONE,
+	.disable_locking = true,
 };
 
 static int realtek_smi_mdio_read(struct mii_bus *bus, int addr, int regnum)
@@ -388,6 +417,7 @@ static int realtek_smi_probe(struct platform_device *pdev)
 	const struct realtek_smi_variant *var;
 	struct device *dev = &pdev->dev;
 	struct realtek_smi *smi;
+	struct regmap_config rc;
 	struct device_node *np;
 	int ret;
 
@@ -398,14 +428,26 @@ static int realtek_smi_probe(struct platform_device *pdev)
 	if (!smi)
 		return -ENOMEM;
 	smi->chip_data = (void *)smi + sizeof(*smi);
-	smi->map = devm_regmap_init(dev, NULL, smi,
-				    &realtek_smi_mdio_regmap_config);
+
+	mutex_init(&smi->map_lock);
+
+	rc = realtek_smi_regmap_config;
+	rc.lock_arg = smi;
+	smi->map = devm_regmap_init(dev, NULL, smi, &rc);
 	if (IS_ERR(smi->map)) {
 		ret = PTR_ERR(smi->map);
 		dev_err(dev, "regmap init failed: %d\n", ret);
 		return ret;
 	}
 
+	rc = realtek_smi_nolock_regmap_config;
+	smi->map_nolock = devm_regmap_init(dev, NULL, smi, &rc);
+	if (IS_ERR(smi->map_nolock)) {
+		ret = PTR_ERR(smi->map_nolock);
+		dev_err(dev, "regmap init failed: %d\n", ret);
+		return ret;
+	}
+
 	/* Link forward and backward */
 	smi->dev = dev;
 	smi->clk_delay = var->clk_delay;
diff --git a/drivers/net/dsa/realtek/realtek-smi-core.h b/drivers/net/dsa/realtek/realtek-smi-core.h
index faed387d8db3..5fcad51e1984 100644
--- a/drivers/net/dsa/realtek/realtek-smi-core.h
+++ b/drivers/net/dsa/realtek/realtek-smi-core.h
@@ -49,6 +49,8 @@ struct realtek_smi {
 	struct gpio_desc	*mdc;
 	struct gpio_desc	*mdio;
 	struct regmap		*map;
+	struct regmap		*map_nolock;
+	struct mutex		map_lock;
 	struct mii_bus		*slave_mii_bus;
 
 	unsigned int		clk_delay;
-- 
2.35.1

[PATCH stable 5.16+ 2/3] net: dsa: realtek: rtl8365mb: serialize indirect PHY register access

[Alvin Šipraga]

From: Alvin Šipraga <alsi@bang-olufsen.dk>

[ Upstream commit 2796728460b822d549841e0341752b263dc265c4 ]

Realtek switches in the rtl8365mb family can access the PHY registers of
the internal PHYs via the switch registers. This method is called
indirect access. At a high level, the indirect PHY register access
method involves reading and writing some special switch registers in a
particular sequence. This works for both SMI and MDIO connected
switches.

Currently the rtl8365mb driver does not take any care to serialize the
aforementioned access to the switch registers. In particular, it is
permitted for other driver code to access other switch registers while
the indirect PHY register access is ongoing. Locking is only done at the
regmap level. This, however, is a bug: concurrent register access, even
to unrelated switch registers, risks corrupting the PHY register value
read back via the indirect access method described above.

Arınç reported that the switch sometimes returns nonsense data when
reading the PHY registers. In particular, a value of 0 causes the
kernel's PHY subsystem to think that the link is down, but since most
reads return correct data, the link then flip-flops between up and down
over a period of time.

The aforementioned bug can be readily observed by:

 1. Enabling ftrace events for regmap and mdio
 2. Polling BSMR PHY register for a connected port;
    it should always read the same (e.g. 0x79ed)
 3. Wait for step 2 to give a different value

Example command for step 2:

    while true; do phytool read swp2/2/0x01; done

On my i.MX8MM, the above steps will yield a bogus value for the BSMR PHY
register within a matter of seconds. The interleaved register access it
then evident in the trace log:

 kworker/3:4-70      [003] .......  1927.139849: regmap_reg_write: ethernet-switch reg=1004 val=bd
     phytool-16816   [002] .......  1927.139979: regmap_reg_read: ethernet-switch reg=1f01 val=0
 kworker/3:4-70      [003] .......  1927.140381: regmap_reg_read: ethernet-switch reg=1005 val=0
     phytool-16816   [002] .......  1927.140468: regmap_reg_read: ethernet-switch reg=1d15 val=a69
 kworker/3:4-70      [003] .......  1927.140864: regmap_reg_read: ethernet-switch reg=1003 val=0
     phytool-16816   [002] .......  1927.140955: regmap_reg_write: ethernet-switch reg=1f02 val=2041
 kworker/3:4-70      [003] .......  1927.141390: regmap_reg_read: ethernet-switch reg=1002 val=0
     phytool-16816   [002] .......  1927.141479: regmap_reg_write: ethernet-switch reg=1f00 val=1
 kworker/3:4-70      [003] .......  1927.142311: regmap_reg_write: ethernet-switch reg=1004 val=be
     phytool-16816   [002] .......  1927.142410: regmap_reg_read: ethernet-switch reg=1f01 val=0
 kworker/3:4-70      [003] .......  1927.142534: regmap_reg_read: ethernet-switch reg=1005 val=0
     phytool-16816   [002] .......  1927.142618: regmap_reg_read: ethernet-switch reg=1f04 val=0
     phytool-16816   [002] .......  1927.142641: mdio_access: SMI-0 read  phy:0x02 reg:0x01 val:0x0000 <- ?!
 kworker/3:4-70      [003] .......  1927.143037: regmap_reg_read: ethernet-switch reg=1001 val=0
 kworker/3:4-70      [003] .......  1927.143133: regmap_reg_read: ethernet-switch reg=1000 val=2d89
 kworker/3:4-70      [003] .......  1927.143213: regmap_reg_write: ethernet-switch reg=1004 val=be
 kworker/3:4-70      [003] .......  1927.143291: regmap_reg_read: ethernet-switch reg=1005 val=0
 kworker/3:4-70      [003] .......  1927.143368: regmap_reg_read: ethernet-switch reg=1003 val=0
 kworker/3:4-70      [003] .......  1927.143443: regmap_reg_read: ethernet-switch reg=1002 val=6

The kworker here is polling MIB counters for stats, as evidenced by the
register 0x1004 that we are writing to (RTL8365MB_MIB_ADDRESS_REG). This
polling is performed every 3 seconds, but is just one example of such
unsynchronized access. In Arınç's case, the driver was not using the
switch IRQ, so the PHY subsystem was itself doing polling analogous to
phytool in the above example.

A test module was created [see second Link] to simulate such spurious
switch register accesses while performing indirect PHY register reads
and writes. Realtek was also consulted to confirm whether this is a
known issue or not. The conclusion of these lines of inquiry is as
follows:

1. Reading of PHY registers via indirect access will be aborted if,
   after executing the read operation (via a write to the
   INDIRECT_ACCESS_CTRL_REG), any register is accessed, other than
   INDIRECT_ACCESS_STATUS_REG.

2. The PHY register indirect read is only complete when
   INDIRECT_ACCESS_STATUS_REG reads zero.

3. The INDIRECT_ACCESS_DATA_REG, which is read to get the result of the
   PHY read, will contain the result of the last successful read
   operation. If there was spurious register access and the indirect
   read was aborted, then this register is not guaranteed to hold
   anything meaningful and the PHY read will silently fail.

4. PHY writes do not appear to be affected by this mechanism.

5. Other similar access routines, such as for MIB counters, although
   similar to the PHY indirect access method, are actually table access.
   Table access is not affected by spurious reads or writes of other
   registers. However, concurrent table access is not allowed. Currently
   this is protected via mib_lock, so there is nothing to fix.

The above statements are corroborated both via the test module and
through consultation with Realtek. In particular, Realtek states that
this is simply a property of the hardware design and is not a hardware
bug.

To fix this problem, one must guard against regmap access while the
PHY indirect register read is executing. Fix this by using the newly
introduced "nolock" regmap in all PHY-related functions, and by aquiring
the regmap mutex at the top level of the PHY register access callbacks.
Although no issue has been observed with PHY register _writes_, this
change also serializes the indirect access method there. This is done
purely as a matter of convenience and for reasons of symmetry.

Fixes: 4af2950c50c8 ("net: dsa: realtek-smi: add rtl8365mb subdriver for RTL8365MB-VC")
Link: https://lore.kernel.org/netdev/CAJq09z5FCgG-+jVT7uxh1a-0CiiFsoKoHYsAWJtiKwv7LXKofQ@mail.gmail.com/
Link: https://lore.kernel.org/netdev/871qzwjmtv.fsf@bang-olufsen.dk/
Reported-by: Arınç ÜNAL <arinc.unal@arinc9.com>
Reported-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[alsi: backport to 5.16: s/priv/smi/g]
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
---
 drivers/net/dsa/realtek/rtl8365mb.c | 54 ++++++++++++++++++-----------
 1 file changed, 33 insertions(+), 21 deletions(-)

diff --git a/drivers/net/dsa/realtek/rtl8365mb.c b/drivers/net/dsa/realtek/rtl8365mb.c
index 48c0e3e46600..3b2d5058b434 100644
--- a/drivers/net/dsa/realtek/rtl8365mb.c
+++ b/drivers/net/dsa/realtek/rtl8365mb.c
@@ -565,7 +565,7 @@ static int rtl8365mb_phy_poll_busy(struct realtek_smi *smi)
 {
 	u32 val;
 
-	return regmap_read_poll_timeout(smi->map,
+	return regmap_read_poll_timeout(smi->map_nolock,
 					RTL8365MB_INDIRECT_ACCESS_STATUS_REG,
 					val, !val, 10, 100);
 }
@@ -579,7 +579,7 @@ static int rtl8365mb_phy_ocp_prepare(struct realtek_smi *smi, int phy,
 	/* Set OCP prefix */
 	val = FIELD_GET(RTL8365MB_PHY_OCP_ADDR_PREFIX_MASK, ocp_addr);
 	ret = regmap_update_bits(
-		smi->map, RTL8365MB_GPHY_OCP_MSB_0_REG,
+		smi->map_nolock, RTL8365MB_GPHY_OCP_MSB_0_REG,
 		RTL8365MB_GPHY_OCP_MSB_0_CFG_CPU_OCPADR_MASK,
 		FIELD_PREP(RTL8365MB_GPHY_OCP_MSB_0_CFG_CPU_OCPADR_MASK, val));
 	if (ret)
@@ -592,8 +592,8 @@ static int rtl8365mb_phy_ocp_prepare(struct realtek_smi *smi, int phy,
 			  ocp_addr >> 1);
 	val |= FIELD_PREP(RTL8365MB_INDIRECT_ACCESS_ADDRESS_OCPADR_9_6_MASK,
 			  ocp_addr >> 6);
-	ret = regmap_write(smi->map, RTL8365MB_INDIRECT_ACCESS_ADDRESS_REG,
-			   val);
+	ret = regmap_write(smi->map_nolock,
+			   RTL8365MB_INDIRECT_ACCESS_ADDRESS_REG, val);
 	if (ret)
 		return ret;
 
@@ -606,36 +606,42 @@ static int rtl8365mb_phy_ocp_read(struct realtek_smi *smi, int phy,
 	u32 val;
 	int ret;
 
+	mutex_lock(&smi->map_lock);
+
 	ret = rtl8365mb_phy_poll_busy(smi);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = rtl8365mb_phy_ocp_prepare(smi, phy, ocp_addr);
 	if (ret)
-		return ret;
+		goto out;
 
 	/* Execute read operation */
 	val = FIELD_PREP(RTL8365MB_INDIRECT_ACCESS_CTRL_CMD_MASK,
 			 RTL8365MB_INDIRECT_ACCESS_CTRL_CMD_VALUE) |
 	      FIELD_PREP(RTL8365MB_INDIRECT_ACCESS_CTRL_RW_MASK,
 			 RTL8365MB_INDIRECT_ACCESS_CTRL_RW_READ);
-	ret = regmap_write(smi->map, RTL8365MB_INDIRECT_ACCESS_CTRL_REG, val);
+	ret = regmap_write(smi->map_nolock, RTL8365MB_INDIRECT_ACCESS_CTRL_REG,
+			   val);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = rtl8365mb_phy_poll_busy(smi);
 	if (ret)
-		return ret;
+		goto out;
 
 	/* Get PHY register data */
-	ret = regmap_read(smi->map, RTL8365MB_INDIRECT_ACCESS_READ_DATA_REG,
-			  &val);
+	ret = regmap_read(smi->map_nolock,
+			  RTL8365MB_INDIRECT_ACCESS_READ_DATA_REG, &val);
 	if (ret)
-		return ret;
+		goto out;
 
 	*data = val & 0xFFFF;
 
-	return 0;
+out:
+	mutex_unlock(&smi->map_lock);
+
+	return ret;
 }
 
 static int rtl8365mb_phy_ocp_write(struct realtek_smi *smi, int phy,
@@ -644,32 +650,38 @@ static int rtl8365mb_phy_ocp_write(struct realtek_smi *smi, int phy,
 	u32 val;
 	int ret;
 
+	mutex_lock(&smi->map_lock);
+
 	ret = rtl8365mb_phy_poll_busy(smi);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = rtl8365mb_phy_ocp_prepare(smi, phy, ocp_addr);
 	if (ret)
-		return ret;
+		goto out;
 
 	/* Set PHY register data */
-	ret = regmap_write(smi->map, RTL8365MB_INDIRECT_ACCESS_WRITE_DATA_REG,
-			   data);
+	ret = regmap_write(smi->map_nolock,
+			   RTL8365MB_INDIRECT_ACCESS_WRITE_DATA_REG, data);
 	if (ret)
-		return ret;
+		goto out;
 
 	/* Execute write operation */
 	val = FIELD_PREP(RTL8365MB_INDIRECT_ACCESS_CTRL_CMD_MASK,
 			 RTL8365MB_INDIRECT_ACCESS_CTRL_CMD_VALUE) |
 	      FIELD_PREP(RTL8365MB_INDIRECT_ACCESS_CTRL_RW_MASK,
 			 RTL8365MB_INDIRECT_ACCESS_CTRL_RW_WRITE);
-	ret = regmap_write(smi->map, RTL8365MB_INDIRECT_ACCESS_CTRL_REG, val);
+	ret = regmap_write(smi->map_nolock, RTL8365MB_INDIRECT_ACCESS_CTRL_REG,
+			   val);
 	if (ret)
-		return ret;
+		goto out;
 
 	ret = rtl8365mb_phy_poll_busy(smi);
 	if (ret)
-		return ret;
+		goto out;
+
+out:
+	mutex_unlock(&smi->map_lock);
 
 	return 0;
 }
-- 
2.35.1

[PATCH stable 5.16+ 3/3] net: dsa: realtek: make interface drivers depend on OF

[Alvin Šipraga]

From: Alvin Šipraga <alsi@bang-olufsen.dk>

[ Upstream commit 109d899452ba17996eccec7ae8249fb1f8900a16 ]

The kernel test robot reported build warnings with a randconfig that
built realtek-{smi,mdio} without CONFIG_OF set. Since both interface
drivers are using OF and will not probe without, add the corresponding
dependency to Kconfig.

Link: https://lore.kernel.org/all/202203231233.Xx73Y40o-lkp@intel.com/
Link: https://lore.kernel.org/all/202203231439.ycl0jg50-lkp@intel.com/
Fixes: aac94001067d ("net: dsa: realtek: add new mdio interface for drivers")
Fixes: 765c39a4fafe ("net: dsa: realtek: convert subdrivers into modules")
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Link: https://lore.kernel.org/r/20220323124225.91763-1-alvin@pqrs.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[alsi: backport to 5.16: remove mdio part]
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
---
 drivers/net/dsa/realtek/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/dsa/realtek/Kconfig b/drivers/net/dsa/realtek/Kconfig
index 1c62212fb0ec..1315896ed6e2 100644
--- a/drivers/net/dsa/realtek/Kconfig
+++ b/drivers/net/dsa/realtek/Kconfig
@@ -14,6 +14,7 @@ menuconfig NET_DSA_REALTEK
 config NET_DSA_REALTEK_SMI
 	tristate "Realtek SMI connected switch driver"
 	depends on NET_DSA_REALTEK
+	depends on OF
 	default y
 	help
 	  Select to enable support for registering switches connected
-- 
2.35.1

Re: [PATCH stable 5.16+ 0/3] backported Realtek DSA driver fixes for 5.16 and 5.17

[Greg Kroah-Hartman]

On Tue, Apr 12, 2022 at 07:32:49PM +0200, Alvin Šipraga wrote:
> From: Alvin Šipraga <alsi@bang-olufsen.dk>
> 
> These fixes can be applied to both 5.16 and 5.17 - the subtree of
> drivers/net/dsa/realtek is identical save for a few unrelated places.
> 
> The main backporting effort was to remove some parts of the patches
> which touched the newly introduced MDIO interface, which was introduced
> in the 5.18 development cycle, and to work around a mass-rename of a
> single variable (smi -> priv). Regrettably this rename will make future
> stable backports equally tedious and hard to automate.
> 
> Please let me know if you would like me to send the series again for
> 5.17.

5.16 is now end-of-life, but I've queued these up for 5.17 now, thanks!

greg k-h