Re: [PATCH] usb: typec: fusb302: Call fusb302_debugfs_init earlier

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

Hi Hans,

On Tue, Aug 13, 2019 at 12:15:24PM +0200, Hans de Goede wrote:
> tcpm_register_port() will call some of the fusb302 code's callbacks
> wich in turn will call fusb302_log(). So we need to call
> fusb302_debugfs_init() before we call tcpm_register_port().
> 
> This fixes the following warning, which was caused by the logbuffer_lock
> not yet being initialized (which is done by fusb302_debugfs_init):
> 
>  DEBUG_LOCKS_WARN_ON(lock->magic != lock)
>  WARNING: CPU: 0 PID: 1306 at kernel/locking/mutex.c:912 __mutex_lock+0x978/0x9a0
>  Modules linked in: fusb302(+) tcpm pi3usb30532 typec bq24190_charger snd_soc_sst_cht_bsw_rt5645 mei_hdcp dwc3 intel_rapl_msr udc_core ulpi gpio_keys intel_powerclamp coretemp kvm_intel brcmfmac kvm brcmutil joydev cfg80211 wdat_wdt irqbypass pcspkr intel_cstate extcon_intel_cht_wc i2c_cht_wc(E) snd_intel_sst_acpi snd_intel_sst_core snd_soc_rt5645 snd_soc_sst_atom_hifi2_platform snd_soc_acpi_intel_match snd_soc_rl6231 snd_soc_acpi intel_xhci_usb_role_switch roles hci_uart snd_soc_core btqca mei_txe btrtl processor_thermal_device mei snd_hdmi_lpe_audio lpc_ich snd_compress btbcm intel_rapl_common ac97_bus dwc3_pci snd_pcm_dmaengine intel_soc_dts_iosf btintel snd_seq bluetooth snd_seq_device snd_pcm intel_cht_int33fe_musb snd_timer intel_cht_int33fe_typec intel_hid intel_cht_int33fe_common sparse_keymap snd ecdh_generic goodix rfkill soundcore ecc spi_pxa2xx_platform max17042_battery dw_dmac int3406_thermal dptf_power acpi_pad soc_button_array int3400_thermal int3403_thermal
>   gpd_pocket_fan intel_int0002_vgpio int340x_thermal_zone acpi_thermal_rel dm_crypt mmc_block i915 crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel i2c_algo_bit drm_kms_helper drm video sdhci_acpi sdhci mmc_core pwm_lpss_platform pwm_lpss i2c_dev
>  CPU: 0 PID: 1306 Comm: systemd-udevd Tainted: G            E     5.3.0-rc4+ #83
>  Hardware name: Default string Default string/Default string, BIOS 5.11 06/28/2017
>  RIP: 0010:__mutex_lock+0x978/0x9a0
>  Code: c0 0f 84 26 f7 ff ff 44 8b 05 24 25 c8 00 45 85 c0 0f 85 16 f7 ff ff 48 c7 c6 da 55 2f ae 48 c7 c7 98 8c 2d ae e8 a0 f9 5c ff <0f> 0b e9 fc f6 ff ff 4c 89 f0 4d 89 fe 49 89 c7 e9 cf fa ff ff e8
>  RSP: 0018:ffffb7a8c0523800 EFLAGS: 00010286
>  RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
>  RDX: 0000000000000002 RSI: 0000000000000001 RDI: 0000000000000246
>  RBP: ffffb7a8c05238c0 R08: 0000000000000000 R09: 0000000000000000
>  R10: ffffb7a8c0523648 R11: 0000000000000030 R12: 0000000000000000
>  R13: ffffb7a8c0523990 R14: ffff9bf22f70c028 R15: ffff9bf22f70c360
>  FS:  00007f39ca234940(0000) GS:ffff9bf237400000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 00007f1f108481a0 CR3: 0000000271f28000 CR4: 00000000001006f0
>  Call Trace:
>   ? find_held_lock+0x39/0x90
>   ? _fusb302_log+0x81/0x1d0 [fusb302]
>   ? vsnprintf+0x3aa/0x4f0
>   ? _fusb302_log+0x81/0x1d0 [fusb302]
>   _fusb302_log+0x81/0x1d0 [fusb302]
>  ...
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/usb/typec/tcpm/fusb302.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
> index ccfc7e91e7a3..04c76b9d0065 100644
> --- a/drivers/usb/typec/tcpm/fusb302.c
> +++ b/drivers/usb/typec/tcpm/fusb302.c
> @@ -1759,6 +1759,7 @@ static int fusb302_probe(struct i2c_client *client,
>  	INIT_WORK(&chip->irq_work, fusb302_irq_work);
>  	INIT_DELAYED_WORK(&chip->bc_lvl_handler, fusb302_bc_lvl_handler_work);
>  	init_tcpc_dev(&chip->tcpc_dev);
> +	fusb302_debugfs_init(chip);
>  
>  	if (client->irq) {
>  		chip->gpio_int_n_irq = client->irq;
> @@ -1784,7 +1785,6 @@ static int fusb302_probe(struct i2c_client *client,
>  		goto tcpm_unregister_port;
>  	}
>  	enable_irq_wake(chip->gpio_int_n_irq);
> -	fusb302_debugfs_init(chip);
>  	i2c_set_clientdata(client, chip);

That leaves the rootdir variable pointing to something again for
example if a failure happens (like -EPROBE_AGAIN) during probe (the
"fusb302" directory is removed, but the rootdir static variable still
points to something).

Let's just create that rootdir directory during driver init. I don't
really understand why should we only create it when/if the first
instance of fusb302 is registered. I think something like this would
work:

diff --git a/drivers/usb/typec/tcpm/fusb302.c b/drivers/usb/typec/tcpm/fusb302.c
index c524088246ee..7a950a6e5f0d 100644
--- a/drivers/usb/typec/tcpm/fusb302.c
+++ b/drivers/usb/typec/tcpm/fusb302.c
@@ -212,9 +212,6 @@ static struct dentry *rootdir;
 static void fusb302_debugfs_init(struct fusb302_chip *chip)
 {
        mutex_init(&chip->logbuffer_lock);
-       if (!rootdir)
-               rootdir = debugfs_create_dir("fusb302", NULL);
-
        chip->dentry = debugfs_create_file(dev_name(chip->dev),
                                           S_IFREG | 0444, rootdir,
                                           chip, &fusb302_debug_fops);
@@ -223,7 +220,6 @@ static void fusb302_debugfs_init(struct fusb302_chip *chip)
 static void fusb302_debugfs_exit(struct fusb302_chip *chip)
 {
        debugfs_remove(chip->dentry);
-       debugfs_remove(rootdir);
 }
 
 #else
@@ -1863,7 +1859,24 @@ static struct i2c_driver fusb302_driver = {
        .remove = fusb302_remove,
        .id_table = fusb302_i2c_device_id,
 };
-module_i2c_driver(fusb302_driver);
+
+static int __init fusb302_init(void)
+{
+       rootdir = debugfs_create_dir("fusb302", NULL);
+       if (IS_ERR(rootdir))
+               return PTR_ERR(rootdir);
+
+       return i2c_add_driver(&fusb302_driver);
+}
+
+static void __exit fusb302_exit(void)
+{
+       i2c_del_driver(&fusb302_driver);
+       debugfs_remove(rootdir);
+}
+
+module_init(fusb302_init);
+module_exit(fusb302_exit);
 
 MODULE_AUTHOR("Yueyao Zhu <yueyao.zhu@gmail.com>");
 MODULE_DESCRIPTION("Fairchild FUSB302 Type-C Chip Driver");


If it's OK, could you include that into this patch?

thanks,

-- 
heikki