Subject: Re: [PATCH] net: stmmac: dwmac-sun8i: fix double disable and unprepare "stmmaceth" clk

From: Jisheng Zhang <[email-masked]>
Date: Thu, 27 Jan 2022 01:31:05 +0800

On Thu, Jan 27, 2022 at 12:00:42AM +0800, Jisheng Zhang wrote:
> On Wed, Jan 26, 2022 at 11:12:28PM +0800, Jisheng Zhang wrote:
> > On Sun, Jan 23, 2022 at 01:43:37PM -0600, Samuel Holland wrote:
> > > On 1/23/22 7:28 AM, Jisheng Zhang wrote:
> > > > Fix warnings on Allwinner D1 platform:
> > > > 
> > > > [    1.604695] ------------[ cut here ]------------
> > > > [    1.609328] bus-emac already disabled
> > > > [    1.613015] WARNING: CPU: 0 PID: 38 at drivers/clk/clk.c:952 clk_core_disable+0xcc/0xec
> > > > [    1.621039] CPU: 0 PID: 38 Comm: kworker/u2:1 Not tainted 5.14.0-rc4#1
> > > > [    1.627653] Hardware name: Allwinner D1 NeZha (DT)
> > > > [    1.632443] Workqueue: events_unbound deferred_probe_work_func
> > > > [    1.638286] epc : clk_core_disable+0xcc/0xec
> > > > [    1.642561]  ra : clk_core_disable+0xcc/0xec
> > > > [    1.646835] epc : ffffffff8023c2ec ra : ffffffff8023c2ec sp : ffffffd00411bb10
> > > > [    1.654054]  gp : ffffffff80ec9988 tp : ffffffe00143a800 t0 : ffffffff80ed6a6f
> > > > [    1.661272]  t1 : ffffffff80ed6a60 t2 : 0000000000000000 s0 : ffffffe001509e00
> > > > [    1.668489]  s1 : 0000000000000001 a0 : 0000000000000019 a1 : ffffffff80e80bd8
> > > > [    1.675707]  a2 : 00000000ffffefff a3 : 00000000000000f4 a4 : 0000000000000002
> > > > [    1.682924]  a5 : 0000000000000001 a6 : 0000000000000030 a7 : 00000000028f5c29
> > > > [    1.690141]  s2 : 0000000000000800 s3 : ffffffe001375000 s4 : ffffffe01fdf7a80
> > > > [    1.697358]  s5 : ffffffe001375010 s6 : ffffffff8001fc10 s7 : ffffffffffffffff
> > > > [    1.704577]  s8 : 0000000000000001 s9 : ffffffff80ecb248 s10: ffffffe001b80000
> > > > [    1.711794]  s11: ffffffe001b80760 t3 : 0000000000000062 t4 : ffffffffffffffff
> > > > [    1.719012]  t5 : ffffffff80e0f6d8 t6 : ffffffd00411b8f0
> > > > [    1.724321] status: 8000000201800100 badaddr: 0000000000000000 cause: 0000000000000003
> > > > [    1.732233] [<ffffffff8023c2ec>] clk_core_disable+0xcc/0xec
> > > > [    1.737810] [<ffffffff80240430>] clk_disable+0x38/0x78
> > > > [    1.742956] [<ffffffff8001fc0c>] worker_thread+0x1a8/0x4d8
> > > > [    1.748451] [<ffffffff8031a500>] stmmac_remove_config_dt+0x1c/0x4c
> > > > [    1.754646] [<ffffffff8031c8ec>] sun8i_dwmac_probe+0x378/0x82c
> > > > [    1.760484] [<ffffffff8001fc0c>] worker_thread+0x1a8/0x4d8
> > > > [    1.765975] [<ffffffff8029a6c8>] platform_probe+0x64/0xf0
> > > > [    1.771382] [<ffffffff8029833c>] really_probe.part.0+0x8c/0x30c
> > > > [    1.777305] [<ffffffff8029865c>] __driver_probe_device+0xa0/0x148
> > > > [    1.783402] [<ffffffff8029873c>] driver_probe_device+0x38/0x138
> > > > [    1.789324] [<ffffffff802989cc>] __device_attach_driver+0xd0/0x170
> > > > [    1.795508] [<ffffffff802988f8>] __driver_attach_async_helper+0xbc/0xc0
> > > > [    1.802125] [<ffffffff802965ac>] bus_for_each_drv+0x68/0xb4
> > > > [    1.807701] [<ffffffff80298d1c>] __device_attach+0xd8/0x184
> > > > [    1.813277] [<ffffffff802967b0>] bus_probe_device+0x98/0xbc
> > > > [    1.818852] [<ffffffff80297904>] deferred_probe_work_func+0x90/0xd4
> > > > [    1.825122] [<ffffffff8001f8b8>] process_one_work+0x1e4/0x390
> > > > [    1.830872] [<ffffffff8001fd80>] worker_thread+0x31c/0x4d8
> > > > [    1.836362] [<ffffffff80026bf4>] kthreadd+0x94/0x188
> > > > [    1.841335] [<ffffffff80026bf4>] kthreadd+0x94/0x188
> > > > [    1.846304] [<ffffffff8001fa60>] process_one_work+0x38c/0x390
> > > > [    1.852054] [<ffffffff80026564>] kthread+0x124/0x160
> > > > [    1.857021] [<ffffffff8002643c>] set_kthread_struct+0x5c/0x60
> > > > [    1.862770] [<ffffffff80001f08>] ret_from_syscall_rejected+0x8/0xc
> > > > [    1.868956] ---[ end trace 8d5c6046255f84a0 ]---
> > > > [    1.873675] ------------[ cut here ]------------
> > > > [    1.878366] bus-emac already unprepared
> > > > [    1.882378] WARNING: CPU: 0 PID: 38 at drivers/clk/clk.c:810 clk_core_unprepare+0xe4/0x168
> > > > [    1.890673] CPU: 0 PID: 38 Comm: kworker/u2:1 Tainted: G        W	5.14.0-rc4 #1
> > > > [    1.898674] Hardware name: Allwinner D1 NeZha (DT)
> > > > [    1.903464] Workqueue: events_unbound deferred_probe_work_func
> > > > [    1.909305] epc : clk_core_unprepare+0xe4/0x168
> > > > [    1.913840]  ra : clk_core_unprepare+0xe4/0x168
> > > > [    1.918375] epc : ffffffff8023d6cc ra : ffffffff8023d6cc sp : ffffffd00411bb10
> > > > [    1.925593]  gp : ffffffff80ec9988 tp : ffffffe00143a800 t0 : 0000000000000002
> > > > [    1.932811]  t1 : ffffffe01f743be0 t2 : 0000000000000040 s0 : ffffffe001509e00
> > > > [    1.940029]  s1 : 0000000000000001 a0 : 000000000000001b a1 : ffffffe00143a800
> > > > [    1.947246]  a2 : 0000000000000000 a3 : 00000000000000f4 a4 : 0000000000000001
> > > > [    1.954463]  a5 : 0000000000000000 a6 : 0000000005fce2a5 a7 : 0000000000000001
> > > > [    1.961680]  s2 : 0000000000000800 s3 : ffffffff80afeb90 s4 : ffffffe01fdf7a80
> > > > [    1.968898]  s5 : ffffffe001375010 s6 : ffffffff8001fc10 s7 : ffffffffffffffff
> > > > [    1.976115]  s8 : 0000000000000001 s9 : ffffffff80ecb248 s10: ffffffe001b80000
> > > > [    1.983333]  s11: ffffffe001b80760 t3 : ffffffff80b39120 t4 : 0000000000000001
> > > > [    1.990550]  t5 : 0000000000000000 t6 : ffffffe001600002
> > > > [    1.995859] status: 8000000201800120 badaddr: 0000000000000000 cause: 0000000000000003
> > > > [    2.003771] [<ffffffff8023d6cc>] clk_core_unprepare+0xe4/0x168
> > > > [    2.009609] [<ffffffff802403a0>] clk_unprepare+0x24/0x3c
> > > > [    2.014929] [<ffffffff8031a508>] stmmac_remove_config_dt+0x24/0x4c
> > > > [    2.021125] [<ffffffff8031c8ec>] sun8i_dwmac_probe+0x378/0x82c
> > > > [    2.026965] [<ffffffff8001fc0c>] worker_thread+0x1a8/0x4d8
> > > > [    2.032463] [<ffffffff8029a6c8>] platform_probe+0x64/0xf0
> > > > [    2.037871] [<ffffffff8029833c>] really_probe.part.0+0x8c/0x30c
> > > > [    2.043795] [<ffffffff8029865c>] __driver_probe_device+0xa0/0x148
> > > > [    2.049892] [<ffffffff8029873c>] driver_probe_device+0x38/0x138
> > > > [    2.055815] [<ffffffff802989cc>] __device_attach_driver+0xd0/0x170
> > > > [    2.061999] [<ffffffff802988f8>] __driver_attach_async_helper+0xbc/0xc0
> > > > [    2.068616] [<ffffffff802965ac>] bus_for_each_drv+0x68/0xb4
> > > > [    2.074193] [<ffffffff80298d1c>] __device_attach+0xd8/0x184
> > > > [    2.079769] [<ffffffff802967b0>] bus_probe_device+0x98/0xbc
> > > > [    2.085345] [<ffffffff80297904>] deferred_probe_work_func+0x90/0xd4
> > > > [    2.091616] [<ffffffff8001f8b8>] process_one_work+0x1e4/0x390
> > > > [    2.097367] [<ffffffff8001fd80>] worker_thread+0x31c/0x4d8
> > > > [    2.102858] [<ffffffff80026bf4>] kthreadd+0x94/0x188
> > > > [    2.107830] [<ffffffff80026bf4>] kthreadd+0x94/0x188
> > > > [    2.112800] [<ffffffff8001fa60>] process_one_work+0x38c/0x390
> > > > [    2.118551] [<ffffffff80026564>] kthread+0x124/0x160
> > > > [    2.123520] [<ffffffff8002643c>] set_kthread_struct+0x5c/0x60
> > > > [    2.129268] [<ffffffff80001f08>] ret_from_syscall_rejected+0x8/0xc
> > > > [    2.135455] ---[ end trace 8d5c6046255f84a1 ]---
> > > > 
> > > > the dwmmac-sun8i driver will get the "stmmaceth" clk as tx_clk during
> > > > driver initialization. If stmmac_dvr_probe() fails due to various
> > > > reasons, sun8i_dwmac_exit() will disable and unprepare the "stmmaceth"
> > > > clk, then stmmac_remove_config_dt() will disable and unprepare the
> > > > clk again.
> > > 
> > > This should still be balanced, because both stmmac_probe_config_dt and
> > > sun8i_dwmac_init prepare/enable the clock, so the dwmac-sun8i glue layer calls
> > > stmmac_dvr_probe with the clock having an enable count of 2. It looks like the
> > > underlying issue is that commit 5ec55823438e ("net: stmmac: add clocks
> > > management for gmac driver") introduces unbalanced runtime PM.
> > 
> > I added some printk then retested, the problem is triggered as below:
> > 
> > stmmac_probe_config_dt() enable the clk
> > sun8i_dwmac_init() enble the clk again
> > stmmac_dvr_probe() succeed, but it calls pm_runtime_put(), so rpm will
> > disable the clk
> > sun8i_dwmac_reset() fails due to various reason
> > sun8i_dwmac_exit() disable the clk, this is fine
> > stmmac_remove_config_dt() disable the clk again, so ccf complains.
> > 
> > The key here is: whether we should let stmmac_dvr_probe() calls
> > pm_runtime_put() or let stmmac users to determine whether we could
> > let rpm go?
> > If we keep current behavior: stmmac users need to take care
> > the code after stmmac_dvr_probe, including error handling code path,
> > if we touch access registers, we need to call pm_runtime_get_sync()
> > firstly.
> > 
> > Since the commit 5ec55823438e has been in for a long time, I'll submit
> > a patch to follow this way.
> > 
> 
> After reading the code and commit history, I found some users suffering
> from the runtimepm issues, for example, dwmac-rk.c, so I changed my
> idea. I think it's better to let stmmac users to call pm_runtime_put():
> 
> First of all, only the users know whether it's safe to finally
> keep the mac runtime suspended after probe.
> 
> Secondly, if the users need to do platform specific operations after
> stmmac_dvr_probe(), especially needs to access some registers, we have
> to resume the mac firstly. The error handling code path also needs to
> take care of it. It looks a bit strange resume immediately resume the
> mac after suspending it.
> 
> Any suggestion is welcome.
> 
> PS: Since this would partially revert commit 5ec55823438e, I add Joakim
> into the email thread.
> 
If we keep current behavior as is, and let stmmac users to take care
necessary runtime resume before specific handling, we need similar
patch as dwmac-sun8i below for all stmmac users, especially the error
handling path:

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
index 09644ab0d87a..ef2acea3d036 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
@@ -16,6 +16,7 @@
 #include <linux/of_net.h>
 #include <linux/phy.h>
 #include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
 #include <linux/regulator/consumer.h>
 #include <linux/regmap.h>
 #include <linux/stmmac.h>
@@ -1254,6 +1255,7 @@ static int sun8i_dwmac_probe(struct platform_device *pdev)
 	ndev = dev_get_drvdata(&pdev->dev);
 	priv = netdev_priv(ndev);
 
+	pm_runtime_get_sync(&pdev->dev);
 	/* The mux must be registered after parent MDIO
 	 * so after stmmac_dvr_probe()
 	 */
@@ -1272,12 +1274,15 @@ static int sun8i_dwmac_probe(struct platform_device *pdev)
 			goto dwmac_remove;
 	}
 
+	pm_runtime_put(&pdev->dev);
+
 	return 0;
 
 dwmac_mux:
 	reset_control_put(gmac->rst_ephy);
 	clk_put(gmac->ephy_clk);
 dwmac_remove:
+	pm_runtime_put_noidle(&pdev->dev);
 	stmmac_dvr_remove(&pdev->dev);
 dwmac_exit:
 	sun8i_dwmac_exit(pdev, gmac);
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 8ded4be08b00..2f9bd1eacb81 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -7133,6 +7133,10 @@ int stmmac_dvr_remove(struct device *dev)
 
 	netdev_info(priv->dev, "%s: removing driver", __func__);
 
+	pm_runtime_get_sync(dev);
+	pm_runtime_disable(dev);
+	pm_runtime_put_noidle(dev);
+
 	stmmac_stop_all_dma(priv);
 	stmmac_mac_set(priv, priv->ioaddr, false);
 	netif_carrier_off(ndev);
@@ -7151,8 +7155,6 @@ int stmmac_dvr_remove(struct device *dev)
 	if (priv->plat->stmmac_rst)
 		reset_control_assert(priv->plat->stmmac_rst);
 	reset_control_assert(priv->plat->stmmac_ahb_rst);
-	pm_runtime_put(dev);
-	pm_runtime_disable(dev);
 	if (priv->hw->pcs != STMMAC_PCS_TBI &&
 	    priv->hw->pcs != STMMAC_PCS_RTBI)
 		stmmac_mdio_unregister(ndev);