[PATCH net-next v2 0/3] Rework GENET MDIO controller clocking

[PATCH net-next v2 0/3] Rework GENET MDIO controller clocking

[Florian Fainelli]

This patch series reworks the way that we manage the GENET MDIO
controller clocks around I/O accesses. During testing with a fully
modular build where bcmgenet, mdio-bcm-unimac, and the Broadcom PHY
driver (broadcom) are all loaded as modules, with no particular care
being taken to order them to mimize deferred probing the following bus
error was obtained:

[    4.344831] printk: console [ttyS0] enabled
[    4.351102] 840d000.serial: ttyS1 at MMIO 0x840d000 (irq = 29, base_baud = 5062500) is a Broadcom BCM7271 UART
[    4.363110] 840e000.serial: ttyS2 at MMIO 0x840e000 (irq = 30, base_baud = 5062500) is a Broadcom BCM7271 UART
[    4.387392] iproc-rng200 8402000.rng: hwrng registered
[    4.398012] Consider using thermal netlink events interface
[    4.403717] brcmstb_thermal a581500.thermal: registered AVS TMON of-sensor driver
[    4.440085] bcmgenet 8f00000.ethernet: GENET 5.0 EPHY: 0x0000
[    4.482526] unimac-mdio unimac-mdio.0: Broadcom UniMAC MDIO bus
[    4.514019] bridge: filtering via arp/ip/ip6tables is no longer available by default. Update your scripts to load br_netfilter if you need this.
[    4.551304] SError Interrupt on CPU2, code 0x00000000bf000002 -- SError
[    4.551324] CPU: 2 PID: 8 Comm: kworker/u8:0 Not tainted 6.1.53-0.1pre-g5a26d98e908c #2
[    4.551330] Hardware name: BCM972180HB_V20 (DT)
[    4.551336] Workqueue: events_unbound deferred_probe_work_func
[    4.551363] pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[    4.551368] pc : el1_abort+0x2c/0x58
[    4.551376] lr : el1_abort+0x20/0x58
[    4.551379] sp : ffffffc00a383960
[    4.551380] x29: ffffffc00a383960 x28: ffffff80029fd780 x27: 0000000000000000
[    4.551385] x26: 0000000000000000 x25: ffffff8002839005 x24: ffffffc00a1f9bd0
[    4.551390] x23: 0000000040000005 x22: ffffffc000a48084 x21: ffffffc00a3dde14
[    4.551394] x20: 0000000096000210 x19: ffffffc00a3839a0 x18: 0000000000000579
[    4.551399] x17: 0000000000000000 x16: 0000000100000000 x15: ffffffc00a3838c0
[    4.551403] x14: 000000000000000a x13: 6e69622f7273752f x12: 3a6e6962732f7273
[    4.551408] x11: 752f3a6e69622f3a x10: 6e6962732f3d4854 x9 : ffffffc0086466a8
[    4.551412] x8 : ffffff80049ee100 x7 : ffffff8003231938 x6 : 0000000000000000
[    4.551416] x5 : 0000002200000000 x4 : ffffffc00a3839a0 x3 : 0000002000000000
[    4.551420] x2 : 0000000000000025 x1 : 0000000096000210 x0 : 0000000000000000
[    4.551429] Kernel panic - not syncing: Asynchronous SError Interrupt
[    4.551432] CPU: 2 PID: 8 Comm: kworker/u8:0 Not tainted 6.1.53-0.1pre-g5a26d98e908c #2
[    4.551435] Hardware name: BCM972180HB_V20 (DT)
[    4.551437] Workqueue: events_unbound deferred_probe_work_func
[    4.551443] Call trace:
[    4.551445]  dump_backtrace+0xe4/0x124
[    4.551452]  show_stack+0x1c/0x28
[    4.551455]  dump_stack_lvl+0x60/0x78
[    4.551462]  dump_stack+0x14/0x2c
[    4.551467]  panic+0x134/0x304
[    4.551472]  nmi_panic+0x50/0x70
[    4.551480]  arm64_serror_panic+0x70/0x7c
[    4.551484]  do_serror+0x2c/0x5c
[    4.551487]  el1h_64_error_handler+0x2c/0x40
[    4.551491]  el1h_64_error+0x64/0x68
[    4.551496]  el1_abort+0x2c/0x58
[    4.551499]  el1h_64_sync_handler+0x8c/0xb4
[    4.551502]  el1h_64_sync+0x64/0x68
[    4.551505]  unimac_mdio_readl.isra.0+0x4/0xc [mdio_bcm_unimac]
[    4.551519]  __mdiobus_read+0x2c/0x88
[    4.551526]  mdiobus_read+0x40/0x60
[    4.551530]  phy_read+0x18/0x20
[    4.551534]  bcm_phy_config_intr+0x20/0x84
[    4.551537]  phy_disable_interrupts+0x2c/0x3c
[    4.551543]  phy_probe+0x80/0x1b0
[    4.551545]  really_probe+0x1b8/0x390
[    4.551550]  __driver_probe_device+0x134/0x14c
[    4.551554]  driver_probe_device+0x40/0xf8
[    4.551559]  __device_attach_driver+0x108/0x11c
[    4.551563]  bus_for_each_drv+0xa4/0xcc
[    4.551567]  __device_attach+0xdc/0x190
[    4.551571]  device_initial_probe+0x18/0x20
[    4.551575]  bus_probe_device+0x34/0x94
[    4.551579]  deferred_probe_work_func+0xd4/0xe8
[    4.551583]  process_one_work+0x1ac/0x25c
[    4.551590]  worker_thread+0x1f4/0x260
[    4.551595]  kthread+0xc0/0xd0
[    4.551600]  ret_from_fork+0x10/0x20
[    4.551608] SMP: stopping secondary CPUs
[    4.551617] Kernel Offset: disabled
[    4.551619] CPU features: 0x00000,00c00080,0000420b
[    4.551622] Memory Limit: none
[    4.833838] ---[ end Kernel panic - not syncing: Asynchronous SError Interrupt ]---

The issue here is that we managed to probe the GENET controller, the
mdio-bcm-unimac MDIO controller, but the PHY was still being held in a
probe deferral state because it depended upon a GPIO controller provider
not loaded yet. As soon as that provider is loaded however, the PHY
continues to probe, tries to disable the interrupts, and this causes a
MDIO transaction. That MDIO transaction requires I/O register accesses
within the GENET's larger block, and since its clocks are turned off,
the CPU gets a bus error signaled as a System Error.

The patch series takes the simplest approach of keeping the clocks
enabled just for the duration of the I/O accesses. This is also
beneficial to other drivers like bcmasp2 which make use of the same MDIO
controller driver.

Changes in v2:

- added missing ret assignment in the if (IS_ERR(priv->clk)) branch

- added Jacob's R-by tags

- corrected the commit ID being reverted in patch #3

Florian Fainelli (3):
  net: mdio: mdio-bcm-unimac: Manage clock around I/O accesses
  net: bcmgenet: Pass "main" clock down to the MDIO driver
  Revert "net: bcmgenet: Ensure MDIO unregistration has clocks enabled"

 drivers/net/ethernet/broadcom/genet/bcmmii.c  |  6 +-
 drivers/net/mdio/mdio-bcm-unimac.c            | 93 ++++++++++---------
 include/linux/platform_data/mdio-bcm-unimac.h |  3 +
 3 files changed, 57 insertions(+), 45 deletions(-)

-- 
2.34.1

[PATCH net-next v2 1/3] net: mdio: mdio-bcm-unimac: Manage clock around I/O accesses

[Florian Fainelli]

Up until now we have managed not to have the mdio-bcm-unimac manage its
clock except during probe and suspend/resume. This works most of the
time, except where it does not.

With a fully modular build, we can get into a situation whereby the
GENET driver is fully registered, and so is the mdio-bcm-unimac driver,
however the Ethernet PHY driver is not yet, because it depends on a
resource that is not yet available (e.g.: GPIO provider). In that state,
the network device is not usable yet, and so to conserve power, the
GENET driver will have turned off its "main" clock which feeds its MDIO
controller.

When the PHY driver finally probes however, we make an access to the PHY
registers to e.g.: disable interrupts, and this causes a bus error
within the MDIO controller space because the MDIO controller clock(s)
are turned off.

To remedy that, we manage the clock around all of the I/O accesses to
the hardware which are done exclusively during read, write and clock
divider configuration.

This ensures that the register space is accessible, and this also
ensures that there are not unnecessarily elevated reference counts
keeping the clocks active when the network device is administratively
turned off. It would be the case with the previous way of managing the
clock.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 drivers/net/mdio/mdio-bcm-unimac.c            | 93 ++++++++++---------
 include/linux/platform_data/mdio-bcm-unimac.h |  3 +
 2 files changed, 53 insertions(+), 43 deletions(-)

diff --git a/drivers/net/mdio/mdio-bcm-unimac.c b/drivers/net/mdio/mdio-bcm-unimac.c
index 68f8ee0ec8ba..6fe08427fdd4 100644
--- a/drivers/net/mdio/mdio-bcm-unimac.c
+++ b/drivers/net/mdio/mdio-bcm-unimac.c
@@ -94,6 +94,10 @@ static int unimac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 	int ret;
 	u32 cmd;
 
+	ret = clk_prepare_enable(priv->clk);
+	if (ret)
+		return ret;
+
 	/* Prepare the read operation */
 	cmd = MDIO_RD | (phy_id << MDIO_PMD_SHIFT) | (reg << MDIO_REG_SHIFT);
 	unimac_mdio_writel(priv, cmd, MDIO_CMD);
@@ -103,7 +107,7 @@ static int unimac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 
 	ret = priv->wait_func(priv->wait_func_data);
 	if (ret)
-		return ret;
+		goto out;
 
 	cmd = unimac_mdio_readl(priv, MDIO_CMD);
 
@@ -112,10 +116,15 @@ static int unimac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
 	 * that condition here and ignore the MDIO controller read failure
 	 * indication.
 	 */
-	if (!(bus->phy_ignore_ta_mask & 1 << phy_id) && (cmd & MDIO_READ_FAIL))
-		return -EIO;
+	if (!(bus->phy_ignore_ta_mask & 1 << phy_id) && (cmd & MDIO_READ_FAIL)) {
+		ret = -EIO;
+		goto out;
+	}
 
-	return cmd & 0xffff;
+	ret = cmd & 0xffff;
+out:
+	clk_disable_unprepare(priv->clk);
+	return ret;
 }
 
 static int unimac_mdio_write(struct mii_bus *bus, int phy_id,
@@ -123,6 +132,11 @@ static int unimac_mdio_write(struct mii_bus *bus, int phy_id,
 {
 	struct unimac_mdio_priv *priv = bus->priv;
 	u32 cmd;
+	int ret;
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret)
+		return ret;
 
 	/* Prepare the write operation */
 	cmd = MDIO_WR | (phy_id << MDIO_PMD_SHIFT) |
@@ -131,7 +145,10 @@ static int unimac_mdio_write(struct mii_bus *bus, int phy_id,
 
 	unimac_mdio_start(priv);
 
-	return priv->wait_func(priv->wait_func_data);
+	ret = priv->wait_func(priv->wait_func_data);
+	clk_disable_unprepare(priv->clk);
+
+	return ret;
 }
 
 /* Workaround for integrated BCM7xxx Gigabit PHYs which have a problem with
@@ -178,14 +195,19 @@ static int unimac_mdio_reset(struct mii_bus *bus)
 	return 0;
 }
 
-static void unimac_mdio_clk_set(struct unimac_mdio_priv *priv)
+static int unimac_mdio_clk_set(struct unimac_mdio_priv *priv)
 {
 	unsigned long rate;
 	u32 reg, div;
+	int ret;
 
 	/* Keep the hardware default values */
 	if (!priv->clk_freq)
-		return;
+		return 0;
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret)
+		return ret;
 
 	if (!priv->clk)
 		rate = 250000000;
@@ -195,7 +217,8 @@ static void unimac_mdio_clk_set(struct unimac_mdio_priv *priv)
 	div = (rate / (2 * priv->clk_freq)) - 1;
 	if (div & ~MDIO_CLK_DIV_MASK) {
 		pr_warn("Incorrect MDIO clock frequency, ignoring\n");
-		return;
+		ret = 0;
+		goto out;
 	}
 
 	/* The MDIO clock is the reference clock (typically 250Mhz) divided by
@@ -205,6 +228,9 @@ static void unimac_mdio_clk_set(struct unimac_mdio_priv *priv)
 	reg &= ~(MDIO_CLK_DIV_MASK << MDIO_CLK_DIV_SHIFT);
 	reg |= div << MDIO_CLK_DIV_SHIFT;
 	unimac_mdio_writel(priv, reg, MDIO_CFG);
+out:
+	clk_disable_unprepare(priv->clk);
+	return ret;
 }
 
 static int unimac_mdio_probe(struct platform_device *pdev)
@@ -235,24 +261,12 @@ static int unimac_mdio_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 
-	priv->clk = devm_clk_get_optional(&pdev->dev, NULL);
-	if (IS_ERR(priv->clk))
-		return PTR_ERR(priv->clk);
-
-	ret = clk_prepare_enable(priv->clk);
-	if (ret)
-		return ret;
-
 	if (of_property_read_u32(np, "clock-frequency", &priv->clk_freq))
 		priv->clk_freq = 0;
 
-	unimac_mdio_clk_set(priv);
-
 	priv->mii_bus = mdiobus_alloc();
-	if (!priv->mii_bus) {
-		ret = -ENOMEM;
-		goto out_clk_disable;
-	}
+	if (!priv->mii_bus)
+		return -ENOMEM;
 
 	bus = priv->mii_bus;
 	bus->priv = priv;
@@ -261,17 +275,29 @@ static int unimac_mdio_probe(struct platform_device *pdev)
 		priv->wait_func = pdata->wait_func;
 		priv->wait_func_data = pdata->wait_func_data;
 		bus->phy_mask = ~pdata->phy_mask;
+		priv->clk = pdata->clk;
 	} else {
 		bus->name = "unimac MII bus";
 		priv->wait_func_data = priv;
 		priv->wait_func = unimac_mdio_poll;
+		priv->clk = devm_clk_get_optional(&pdev->dev, NULL);
+	}
+
+	if (IS_ERR(priv->clk)) {
+		ret = PTR_ERR(priv->clk);
+		goto out_mdio_free;
 	}
+
 	bus->parent = &pdev->dev;
 	bus->read = unimac_mdio_read;
 	bus->write = unimac_mdio_write;
 	bus->reset = unimac_mdio_reset;
 	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-%d", pdev->name, pdev->id);
 
+	ret = unimac_mdio_clk_set(priv);
+	if (ret)
+		goto out_mdio_free;
+
 	ret = of_mdiobus_register(bus, np);
 	if (ret) {
 		dev_err(&pdev->dev, "MDIO bus registration failed\n");
@@ -286,8 +312,6 @@ static int unimac_mdio_probe(struct platform_device *pdev)
 
 out_mdio_free:
 	mdiobus_free(bus);
-out_clk_disable:
-	clk_disable_unprepare(priv->clk);
 	return ret;
 }
 
@@ -297,34 +321,17 @@ static void unimac_mdio_remove(struct platform_device *pdev)
 
 	mdiobus_unregister(priv->mii_bus);
 	mdiobus_free(priv->mii_bus);
-	clk_disable_unprepare(priv->clk);
-}
-
-static int __maybe_unused unimac_mdio_suspend(struct device *d)
-{
-	struct unimac_mdio_priv *priv = dev_get_drvdata(d);
-
-	clk_disable_unprepare(priv->clk);
-
-	return 0;
 }
 
 static int __maybe_unused unimac_mdio_resume(struct device *d)
 {
 	struct unimac_mdio_priv *priv = dev_get_drvdata(d);
-	int ret;
 
-	ret = clk_prepare_enable(priv->clk);
-	if (ret)
-		return ret;
-
-	unimac_mdio_clk_set(priv);
-
-	return 0;
+	return unimac_mdio_clk_set(priv);
 }
 
 static SIMPLE_DEV_PM_OPS(unimac_mdio_pm_ops,
-			 unimac_mdio_suspend, unimac_mdio_resume);
+			 NULL, unimac_mdio_resume);
 
 static const struct of_device_id unimac_mdio_ids[] = {
 	{ .compatible = "brcm,asp-v2.1-mdio", },
diff --git a/include/linux/platform_data/mdio-bcm-unimac.h b/include/linux/platform_data/mdio-bcm-unimac.h
index 8a5f9f0b2c52..724e1f57b81f 100644
--- a/include/linux/platform_data/mdio-bcm-unimac.h
+++ b/include/linux/platform_data/mdio-bcm-unimac.h
@@ -1,11 +1,14 @@
 #ifndef __MDIO_BCM_UNIMAC_PDATA_H
 #define __MDIO_BCM_UNIMAC_PDATA_H
 
+struct clk;
+
 struct unimac_mdio_pdata {
 	u32 phy_mask;
 	int (*wait_func)(void *data);
 	void *wait_func_data;
 	const char *bus_name;
+	struct clk *clk;
 };
 
 #define UNIMAC_MDIO_DRV_NAME	"unimac-mdio"
-- 
2.34.1

[PATCH net-next v2 2/3] net: bcmgenet: Pass "main" clock down to the MDIO driver

[Florian Fainelli]

GENET has historically had to create a MDIO platform device for its
controller and pass some auxiliary data to it, like a MDIO completion
callback. Now we also pass the "main" clock to allow for the MDIO bus
controller to manage that clock adequately around I/O accesses.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 drivers/net/ethernet/broadcom/genet/bcmmii.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmmii.c b/drivers/net/ethernet/broadcom/genet/bcmmii.c
index cbbe004621bc..7a21950da77c 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmmii.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmmii.c
@@ -476,6 +476,10 @@ static int bcmgenet_mii_register(struct bcmgenet_priv *priv)
 	ppd.wait_func = bcmgenet_mii_wait;
 	ppd.wait_func_data = priv;
 	ppd.bus_name = "bcmgenet MII bus";
+	/* Pass a reference to our "main" clock which is used for MDIO
+	 * transfers
+	 */
+	ppd.clk = priv->clk;
 
 	/* Unimac MDIO bus controller starts at UniMAC offset + MDIO_CMD
 	 * and is 2 * 32-bits word long, 8 bytes total.
-- 
2.34.1

[PATCH net-next v2 3/3] Revert "net: bcmgenet: Ensure MDIO unregistration has clocks enabled"

[Florian Fainelli]

This reverts commit 1b5ea7ffb7a3bdfffb4b7f40ce0d20a3372ee405 ("net:
bcmgenet: Ensure MDIO unregistration has clocks enabled"). This is no
longer necessary now that the MDIO bus controller has a clock that it
can manage around the I/O accesses.

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
 drivers/net/ethernet/broadcom/genet/bcmmii.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmmii.c b/drivers/net/ethernet/broadcom/genet/bcmmii.c
index 7a21950da77c..9ada89355747 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmmii.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmmii.c
@@ -678,7 +678,5 @@ void bcmgenet_mii_exit(struct net_device *dev)
 	if (of_phy_is_fixed_link(dn))
 		of_phy_deregister_fixed_link(dn);
 	of_node_put(priv->phy_dn);
-	clk_prepare_enable(priv->clk);
 	platform_device_unregister(priv->mii_pdev);
-	clk_disable_unprepare(priv->clk);
 }
-- 
2.34.1

Re: [PATCH net-next v2 0/3] Rework GENET MDIO controller clocking

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Mon, 19 Feb 2024 12:40:50 -0800 you wrote:
> This patch series reworks the way that we manage the GENET MDIO
> controller clocks around I/O accesses. During testing with a fully
> modular build where bcmgenet, mdio-bcm-unimac, and the Broadcom PHY
> driver (broadcom) are all loaded as modules, with no particular care
> being taken to order them to mimize deferred probing the following bus
> error was obtained:
> 
> [...]

Here is the summary with links:
  - [net-next,v2,1/3] net: mdio: mdio-bcm-unimac: Manage clock around I/O accesses
    https://git.kernel.org/netdev/net-next/c/ee975351cf0c
  - [net-next,v2,2/3] net: bcmgenet: Pass "main" clock down to the MDIO driver
    https://git.kernel.org/netdev/net-next/c/ee2b4cf8b281
  - [net-next,v2,3/3] Revert "net: bcmgenet: Ensure MDIO unregistration has clocks enabled"
    https://git.kernel.org/netdev/net-next/c/ba0b78371c46

You are awesome, thank you!
-- 
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