Messages in this thread | | | Date | Wed, 27 Jul 2022 14:51:24 -0700 | Subject | Re: bcm2711_thermal: Kernel panic - not syncing: Asynchronous SError Interrupt | From | Florian Fainelli <> |
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On 7/27/22 01:05, Juerg Haefliger wrote: > On Wed, 10 Feb 2021 14:59:45 -0800 > Florian Fainelli <f.fainelli@gmail.com> wrote: > >> On 2/10/2021 8:55 AM, Nicolas Saenz Julienne wrote: >>> Hi Robin, >>> >>> On Wed, 2021-02-10 at 16:25 +0000, Robin Murphy wrote: >>>> On 2021-02-10 13:15, Nicolas Saenz Julienne wrote: >>>>> [ Add Robin, Catalin and Florian in case they want to chime in ] >>>>> >>>>> Hi Juerg, thanks for the report! >>>>> >>>>> On Wed, 2021-02-10 at 11:48 +0100, Juerg Haefliger wrote: >>>>>> Trying to dump the BCM2711 registers kills the kernel: >>>>>> >>>>>> # cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2000/range >>>>>> 0-efc >>>>>> # cat /sys/kernel/debug/regmap/dummy-avs-monitor\@fd5d2000/registers >>>>>> >>>>>> [ 62.857661] SError Interrupt on CPU1, code 0xbf000002 -- SError >>>>> >>>>> So ESR's IDS (bit 24) is set, which means it's an 'Implementation Defined >>>>> SError,' hence IIUC the rest of the error code is meaningless to anyone outside >>>>> of Broadcom/RPi. >>>> >>>> It's imp-def from the architecture's PoV, but the implementation in this >>>> case is Cortex-A72, where 0x000002 means an attributable, containable >>>> Slave Error: >>>> >>>> https://developer.arm.com/documentation/100095/0003/system-control/aarch64-register-descriptions/exception-syndrome-register--el1-and-el3?lang=en >>>> >>>> In other words, the thing at the other end of an interconnect >>>> transaction said "no" :) >>>> >>>> (The fact that Cortex-A72 gets too far ahead of itself to take it as a >>>> synchronous external abort is a mild annoyance, but hey...) >>> >>> Thanks for both your clarifications! Reading arm documentation is a skill on >>> its own. >> >> Yes it is. >> >>> >>>>> The regmap is created through the following syscon device: >>>>> >>>>> avs_monitor: avs-monitor@7d5d2000 { >>>>> compatible = "brcm,bcm2711-avs-monitor", >>>>> "syscon", "simple-mfd"; >>>>> reg = <0x7d5d2000 0xf00>; >>>>> >>>>> thermal: thermal { >>>>> compatible = "brcm,bcm2711-thermal"; >>>>> #thermal-sensor-cells = <0>; >>>>> }; >>>>> }; >>>>> >>>>> I've done some tests with devmem, and the whole <0x7d5d2000 0xf00> range is >>>>> full of addresses that trigger this same error. Also note that as per Florian's >>>>> comments[1]: "AVS_RO_REGISTERS_0: 0x7d5d2200 - 0x7d5d22e3." But from what I can >>>>> tell, at least 0x7d5d22b0 seems to be faulty too. >>>>> >>>>> Any ideas/comments? My guess is that those addresses are marked somehow as >>>>> secure, and only for VC4 to access (VC4 is RPi4's co-processor). Ultimately, >>>>> the solution is to narrow the register range exposed by avs-monitor to whatever >>>>> bcm2711-thermal needs (which is ATM a single 32bit register). >>>> >>>> When a peripheral decodes a region of address space, nobody says it has >>>> to accept accesses to *every* address in that space; registers may be >>>> sparsely populated, and although some devices might be "nice" and make >>>> unused areas behave as RAZ/WI, others may throw slave errors if you poke >>>> at the wrong places. As you note, in a TrustZone-aware device some >>>> registers may only exist in one or other of the Secure/Non-Secure >>>> address spaces. >>>> >>>> Even when there is a defined register at a given address, it still >>>> doesn't necessarily accept all possible types of access; it wouldn't be >>>> particularly friendly, but a device *could* have, say, some registers >>>> that support 32-bit accesses and others that only support 16-bit >>>> accesses, and thus throw slave errors if you do the wrong thing in the >>>> wrong place. >>>> >>>> It really all depends on the device itself. >>> >>> All in all, assuming there is no special device quirk to apply, the feeling I'm >>> getting is to just let the error be. As you hint, firmware has no blame here, >>> and debugfs is a 'best effort, zero guarantees' interface after all. >> >> We should probably fill a regmap_access_table to deny reading registers >> for which there is no address decoding and possibly another one to deny >> writing to the read-only registers. > > > Below is a patch that adds a read access table but it seems wrong to include > 'internal.h' and add the table in the thermal driver. Shouldn't this happen > in a higher layer, somehow between syscon and the thermal node?
What is the purpose of doing doing this though that cannot already be done using devmem/devmem2 if the point is explore the address space? -- Florian
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