Re: kern/57063: Kernel panic in -current in iic_attach

[Brad Spencer <brad%anduin.eldar.org@localhost>]

The following reply was made to PR kern/57063; it has been noted by GNATS.

From: Brad Spencer <brad%anduin.eldar.org@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost, gnats-admin%netbsd.org@localhost, netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/57063: Kernel panic in -current in iic_attach
Date: Tue, 18 Oct 2022 10:17:44 -0400

 Taylor R Campbell <riastradh%NetBSD.org@localhost> writes:
 
 > The following reply was made to PR kern/57063; it has been noted by GNATS.
 >
 > From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
 > To: brad%anduin.eldar.org@localhost
 > Cc: gnats-bugs%NetBSD.org@localhost, bouyer%NetBSD.org@localhost
 > Subject: Re: kern/57063: Kernel panic in -current in iic_attach
 > Date: Tue, 18 Oct 2022 10:16:28 +0000
 >
 >  > kernel: page fault trap, code=3D0
 >  > Stopped in pid 0.0 (system) at  netbsd:iic_attach+0x64: movq    %rax,70(%=
 >  r12)
 >  > iic_attach() at netbsd:iic_attach
 >  
 >  This is almost certainly because something in dwiic_attach failed, but
 >  pci_dwiic_attach blithely ignored the failure and barged ahead trying
 >  to attach a child with unininitialized i2cbus_attach_args having a
 >  null i2c tag:
 >  
 >  https://nxr.netbsd.org/xref/src/sys/arch/x86/pci/dwiic_pci.c?r=3D1.8#280
 >  
 >      280 	dwiic_attach(&sc->sc_dwiic);
 >      281=20
 >      282 	config_found(self, &sc->sc_dwiic.sc_iba, iicbus_print, CFARGS_NONE=
 >  );
 >  
 
 
 I looked into this some more.  If you leave out dwiic from the kernel,
 the panic goes away, so that confirms that it is dwiic.
 
 I messed with the code for a while until I really needed the DOM0
 functional and this is what I noted:
 
 o The driver wants a device that returns 0x44570140 in the
 DW_IC_COMP_TYPE register
 
 o My device returns 0xf000eef3 in that register, so the driver fails in
 dwiic_init
 
 o Upon failing in dwiic_init a 1 is returned back to dwiic_attach and
 back to pci_dwiic_attach.  However, none of the sub-drivers for PCI,
 ACPI or FDT catch this fail and do the config anyway as Taylor noted.
 
 o If you do the obvious:
 
 
 --- dwiic_pci.c.DIST    2021-10-28 06:59:10.187238063 -0400
 +++ dwiic_pci.c 2022-10-18 08:31:42.976592974 -0400
 @@ -277,11 +277,10 @@
                 aprint_verbose_dev(self, "no matching ACPI node\n");
         }
  
 -       dwiic_attach(&sc->sc_dwiic);
 -
 -       config_found(self, &sc->sc_dwiic.sc_iba, iicbus_print, CFARGS_NONE);
 -
 -       pmf_device_register(self, dwiic_suspend, dwiic_resume);
 +       if (dwiic_attach(&sc->sc_dwiic)) {
 +               config_found(self, &sc->sc_dwiic.sc_iba, iicbus_print, CFARGS_NONE);
 +               pmf_device_register(self, dwiic_suspend, dwiic_resume);
 +       }
  
  out:
         return;
 
 you will avoid the panic I send-pr'ed about, but will panic later
 because the interrupts are apparently set up and a crash occurs in
 dwiic_intr (assuming I read the screen correctly) at a later time.
 
 o If you comment out the type check in dwiic_init and and try to use the
 device I have anyway you do not appear to get a panic anywhere, but the
 driver reports fails in other ways indicating that the device I have
 really won't work with the driver:
 
 [     1.000003] dwiic0 at pci0 dev 21 function 0: I2C controller instance 0
 [     1.000003] dwiic0: interrupting at ioapic0 pin 16
 [     1.000003] dwiic0: failed to disable
 [     1.000003] dwiic0: failed to disable
 [     1.000003] iic0 at dwiic0: I2C bus
 [     1.000003] dwiic1 at pci0 dev 21 function 1autoconfiguration error: : can't map register space
 
 
 
 
 -- 
 Brad Spencer - brad%anduin.eldar.org@localhost - KC8VKS - http://anduin.eldar.org