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

From: Jisheng Zhang <[email-masked]>
Date: Wed, 26 Jan 2022 23:12:15 +0800

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.

Thanks
>  - stmmac_dvr_probe calls pm_runtime_get_noresume and pm_runtime_set_active,
> since it assumes the clocks are already enabled. This is fine.
>  - If stmmac_dvr_probe fails, it calls stmmac_bus_clks_config(priv, false),
> which drops the enable count down to 1. This is a bug, not just in this case,
> but also because it will unbalance the clocks if runtime PM is disabled.
>  - If stmmac_dvr_probe fails, it never calls pm_runtime_disable if the failure
> occurs after the call to pm_runtime_enable. This is also a bug.
> 
> It looks like at some point stmmac_dvr_remove was expected to leave all of the
> clocks disabled, but it must leave them enabled as of commit 8f269102baf7 ("net:
> stmmac: disable clocks in stmmac_remove_config_dt()"), since
> stmmac_remove_config_dt is called after stmmac_dvr_remove in stmmac_pltfr_remove.
>  - If stmmac_dvr_probe succeeds, it calls pm_runtime_put. This allows runtime PM
> to suspend the device, dropping the clock enable count to 1. This is fine.
>  - But then stmmac_dvr_remove calls pm_runtime_put as well. It needs to do the
> opposite. It must ensure the device is runtime resumed, so the clock enable
> count matches what it was before stmmac_dvr_probe was called (in this case: 2).
> 
> > Currently, there's no other usage of tx_clk except preparing and
> > enabling, we can fix the above warnings by simply removing the tx_clk
> > and all its usage, we rely on the common stmmac_probe_config_dt()
> > routine to prepare and enable the stmmaceth clk.
> 
> This is a good change to make, as indeed this code is now unnecessary, and
> removing it will allow runtime PM to actually disable the clock. But I am not
> sure how this resolves the warnings you are seeing, as the sun8i_dwmac_init/exit
> calls should have been balanced already.
> 
> Can you check if the PHY regulator is also getting unbalanced? Unbalanced calls
> to sun8i_dwmac_exit would also underflow the regulator use count, which should
> trigger its own warning.
> 
> Regards,
> Samuel
> 
> > Signed-off-by: Jisheng Zhang <[email-masked]>
> > ---
> >  .../net/ethernet/stmicro/stmmac/dwmac-sun8i.c | 20 +------------------
> >  1 file changed, 1 insertion(+), 19 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> > index 617d0e4c6495..d97469825e53 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sun8i.c
> > @@ -57,7 +57,6 @@ struct emac_variant {
> >  };
> >  
> >  /* struct sunxi_priv_data - hold all sunxi private data
> > - * @tx_clk:	reference to MAC TX clock
> >   * @ephy_clk:	reference to the optional EPHY clock for the internal PHY
> >   * @regulator:	reference to the optional regulator
> >   * @rst_ephy:	reference to the optional EPHY reset for the internal PHY
> > @@ -68,7 +67,6 @@ struct emac_variant {
> >   * @mux_handle:	Internal pointer used by mdio-mux lib
> >   */
> >  struct sunxi_priv_data {
> > -	struct clk *tx_clk;
> >  	struct clk *ephy_clk;
> >  	struct regulator *regulator;
> >  	struct reset_control *rst_ephy;
> > @@ -579,22 +577,14 @@ static int sun8i_dwmac_init(struct platform_device *pdev, void *priv)
> >  		}
> >  	}
> >  
> > -	ret = clk_prepare_enable(gmac->tx_clk);
> > -	if (ret) {
> > -		dev_err(&pdev->dev, "Could not enable AHB clock\n");
> > -		goto err_disable_regulator;
> > -	}
> > -
> >  	if (gmac->use_internal_phy) {
> >  		ret = sun8i_dwmac_power_internal_phy(netdev_priv(ndev));
> >  		if (ret)
> > -			goto err_disable_clk;
> > +			goto err_disable_regulator;
> >  	}
> >  
> >  	return 0;
> >  
> > -err_disable_clk:
> > -	clk_disable_unprepare(gmac->tx_clk);
> >  err_disable_regulator:
> >  	if (gmac->regulator)
> >  		regulator_disable(gmac->regulator);
> > @@ -1043,8 +1033,6 @@ static void sun8i_dwmac_exit(struct platform_device *pdev, void *priv)
> >  	if (gmac->variant->soc_has_internal_phy)
> >  		sun8i_dwmac_unpower_internal_phy(gmac);
> >  
> > -	clk_disable_unprepare(gmac->tx_clk);
> > -
> >  	if (gmac->regulator)
> >  		regulator_disable(gmac->regulator);
> >  }
> > @@ -1167,12 +1155,6 @@ static int sun8i_dwmac_probe(struct platform_device *pdev)
> >  		return -EINVAL;
> >  	}
> >  
> > -	gmac->tx_clk = devm_clk_get(dev, "stmmaceth");
> > -	if (IS_ERR(gmac->tx_clk)) {
> > -		dev_err(dev, "Could not get TX clock\n");
> > -		return PTR_ERR(gmac->tx_clk);
> > -	}
> > -
> >  	/* Optional regulator for PHY */
> >  	gmac->regulator = devm_regulator_get_optional(dev, "phy");
> >  	if (IS_ERR(gmac->regulator)) {
> > 
>