Re: [PATCH v3] usb: dwc3: core: Fix system suspend on TI AM62 platforms

[William McVicker <willmcvicker@google.com>]

+linux-arm-msm@vger.kernel.org

Hi Roger,

On 10/11/2024, Roger Quadros wrote:
> Since commit 6d735722063a ("usb: dwc3: core: Prevent phy suspend during init"),
> system suspend is broken on AM62 TI platforms.
> 
> Before that commit, both DWC3_GUSB3PIPECTL_SUSPHY and DWC3_GUSB2PHYCFG_SUSPHY
> bits (hence forth called 2 SUSPHY bits) were being set during core
> initialization and even during core re-initialization after a system
> suspend/resume.
> 
> These bits are required to be set for system suspend/resume to work correctly
> on AM62 platforms.
> 
> Since that commit, the 2 SUSPHY bits are not set for DEVICE/OTG mode if gadget
> driver is not loaded and started.
> For Host mode, the 2 SUSPHY bits are set before the first system suspend but
> get cleared at system resume during core re-init and are never set again.
> 
> This patch resovles these two issues by ensuring the 2 SUSPHY bits are set
> before system suspend and restored to the original state during system resume.
> 
> Cc: stable@vger.kernel.org # v6.9+
> Fixes: 6d735722063a ("usb: dwc3: core: Prevent phy suspend during init")
> Link: https://lore.kernel.org/all/1519dbe7-73b6-4afc-bfe3-23f4f75d772f@kernel.org/
> Signed-off-by: Roger Quadros <rogerq@kernel.org>
> Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
> ---
> Changes in v3:
> - Fix single line comment style
> - add DWC3_GUSB3PIPECTL_SUSPHY to documentation of susphy_state
> - Added Acked-by tag
> - Link to v2: https://lore.kernel.org/r/20241009-am62-lpm-usb-v2-1-da26c0cd2b1e@kernel.org
> 
> Changes in v2:
> - Fix comment style
> - Use both USB3 and USB2 SUSPHY bits to determine susphy_state during system suspend/resume.
> - Restore SUSPHY bits at system resume regardless if it was set or cleared before system suspend.
> - Link to v1: https://lore.kernel.org/r/20241001-am62-lpm-usb-v1-1-9916b71165f7@kernel.org
> ---
>  drivers/usb/dwc3/core.c | 19 +++++++++++++++++++
>  drivers/usb/dwc3/core.h |  3 +++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index 9eb085f359ce..ca77f0b186c4 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -2336,6 +2336,11 @@ static int dwc3_suspend_common(struct dwc3 *dwc, pm_message_t msg)
>  	u32 reg;
>  	int i;
>  
> +	dwc->susphy_state = (dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0)) &
> +			    DWC3_GUSB2PHYCFG_SUSPHY) ||
> +			    (dwc3_readl(dwc->regs, DWC3_GUSB3PIPECTL(0)) &
> +			    DWC3_GUSB3PIPECTL_SUSPHY);
> +

I'm running into an issue on my Pixel 6 device with this change when the
dwc3-exynos device has runtime PM enabled. Basically, after the device boots up
and I disconnect USB, the dwc3-exynos device enters runtime suspend followed by
system suspend 15 seconds later. On system suspend, the clocks powering these
dwc3 registers are off which results in an SError. I have verified that
reverting this change fixes the issue.

I noticed that dwc3-qcom.c also supports runtime PM for their dwc3 device and
most likely is affected by this as well. It would be great if someone with a
Qualcomm device could test out dwc3 suspend as well.

Here is the crash stack:

  SError Interrupt on CPU7, code 0x00000000be000011 -- SError
  CPU: 7 UID: 1000 PID: 5661 Comm: binder:477_1 Tainted: G        W  OE      6.12.0-rc3-android16-0-maybe-dirty-4k #1 0439eacb3cff642033630df7ee2e250e0625f2f0
  96 irq, BUS_DATA0 group, 0x0
  Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
  Hardware name: Raven DVT (DT)
  pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  pc : readl+0x40/0x80
  lr : readl+0x38/0x80
  sp : ffffffc08baa39a0
  x29: ffffffc08baa39a0 x28: ffffffd4dd140000 x27: ffffffd4dd140d70
  x26: ffffffd4dd2b2000 x25: ffffff800cef2410 x24: ffffff800cef24c0
  x23: ffffffd4dd24e000 x22: ffffff887df59440 x21: ffffffc085298100
  x20: ffffffd4db8acf60 x19: ffffffc085298200 x18: ffffffc091b730b0
  x17: 000000002a703c0b x16: 000000002a703c0b x15: 0000000000953000
  x14: 0000000000000000 x13: 0000000000000030 x12: 0101010101010101
  x11: 7f7f7f7f7f7fffff x10: 0000000000000000 x9 : ffffffd4dc0d7d48
  x8 : 0000000000000000 x7 : 0000000000008000 x6 : 0000000000000000
  x5 : 500020737562ffff x4 : 500020737562ffff x3 : ffffffd4db8acf60
  x2 : ffffffd4db8a7bac x1 : ffffffc085298200 x0 : 0000000000000020
  Kernel panic - not syncing: Asynchronous SError Interrupt
  CPU: 7 UID: 1000 PID: 5661 Comm: binder:477_1 Tainted: G        W  OE      6.12.0-rc3-android16-0-maybe-dirty-4k #1 0439eacb3cff642033630df7ee2e250e0625f2f0
  Tainted: [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
  Hardware name: Raven DVT (DT)
  Call trace:
   dump_backtrace+0xec/0x128
   show_stack+0x18/0x28
   dump_stack_lvl+0x40/0x88
   dump_stack+0x18/0x24
   panic+0x134/0x45c
   nmi_panic+0x3c/0x88
   arm64_serror_panic+0x64/0x8c
   do_serror+0xc4/0xc8
   el1h_64_error_handler+0x34/0x48
   el1h_64_error+0x68/0x6c
   readl+0x40/0x80
   dwc3_suspend_common+0x34/0x454
   dwc3_suspend+0x20/0x40
   platform_pm_suspend+0x40/0x90
   dpm_run_callback+0x60/0x250
   device_suspend+0x334/0x614
   dpm_suspend+0xc4/0x368
   dpm_suspend_start+0x90/0x100
   suspend_devices_and_enter+0x128/0xad0
   pm_suspend+0x354/0x650
   state_store+0x104/0x144
   kobj_attr_store+0x30/0x48
   sysfs_kf_write+0x54/0x6c
   kernfs_fop_write_iter+0x104/0x1e4
   vfs_write+0x3bc/0x50c
   ksys_write+0x78/0xe8
   __arm64_sys_write+0x1c/0x2c
   invoke_syscall+0x58/0x10c
   el0_svc_common+0xa8/0xdc
   do_el0_svc+0x1c/0x28
   el0_svc+0x38/0x6c
   el0t_64_sync_handler+0x70/0xbc
   el0t_64_sync+0x1a8/0x1ac

Thanks,
Will

<snip>