linux-kernel - Re: [PATCH v3] mips: bmips: BCM6358: disable RAC flush for TP1

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Date:   Fri, 17 Mar 2023 09:44:54 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Álvaro Fernández Rojas <noltari@...il.com>,
        f.fainelli@...il.com, jonas.gorski@...il.com,
        bcm-kernel-feedback-list@...adcom.com, tsbogend@...ha.franken.de,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] mips: bmips: BCM6358: disable RAC flush for TP1

On 3/17/23 03:20, Álvaro Fernández Rojas wrote:
> RAC flush causes kernel panics on BCM6358 with EHCI/OHCI when booting from TP1:
> [    3.881739] usb 1-1: new high-speed USB device number 2 using ehci-platform
> [    3.895011] Reserved instruction in kernel code[#1]:
> [    3.900113] CPU: 0 PID: 1 Comm: init Not tainted 5.10.16 #0
> [    3.905829] $ 0   : 00000000 10008700 00000000 77d94060
> [    3.911238] $ 4   : 7fd1f088 00000000 81431cac 81431ca0
> [    3.916641] $ 8   : 00000000 ffffefff 8075cd34 00000000
> [    3.922043] $12   : 806f8d40 f3e812b7 00000000 000d9aaa
> [    3.927446] $16   : 7fd1f068 7fd1f080 7ff559b8 81428470
> [    3.932848] $20   : 00000000 00000000 55590000 77d70000
> [    3.938251] $24   : 00000018 00000010
> [    3.943655] $28   : 81430000 81431e60 81431f28 800157fc
> [    3.949058] Hi    : 00000000
> [    3.952013] Lo    : 00000000
> [    3.955019] epc   : 80015808 setup_sigcontext+0x54/0x24c
> [    3.960464] ra    : 800157fc setup_sigcontext+0x48/0x24c
> [    3.965913] Status: 10008703	KERNEL EXL IE
> [    3.970216] Cause : 00800028 (ExcCode 0a)
> [    3.974340] PrId  : 0002a010 (Broadcom BMIPS4350)
> [    3.979170] Modules linked in: ohci_platform ohci_hcd fsl_mph_dr_of ehci_platform ehci_fsl ehci_hcd gpio_button_hotplug usbcore nls_base usb_common
> [    3.992907] Process init (pid: 1, threadinfo=(ptrval), task=(ptrval), tls=77e22ec8)
> [    4.000776] Stack : 81431ef4 7fd1f080 81431f28 81428470 7fd1f068 81431edc 7ff559b8 81428470
> [    4.009467]         81431f28 7fd1f080 55590000 77d70000 77d5498c 80015c70 806f0000 8063ae74
> [    4.018149]         08100002 81431f28 0000000a 08100002 81431f28 0000000a 77d6b418 00000003
> [    4.026831]         ffffffff 80016414 80080734 81431ecc 81431ecc 00000001 00000000 04000000
> [    4.035512]         77d54874 00000000 00000000 00000000 00000000 00000012 00000002 00000000
> [    4.044196]         ...
> [    4.046706] Call Trace:
> [    4.049238] [<80015808>] setup_sigcontext+0x54/0x24c
> [    4.054356] [<80015c70>] setup_frame+0xdc/0x124
> [    4.059015] [<80016414>] do_notify_resume+0x1dc/0x288
> [    4.064207] [<80011b50>] work_notifysig+0x10/0x18
> [    4.069036]
> [    4.070538] Code: 8fc300b4  00001025  26240008 <ac820000> ac830004  3c048063  0c0228aa  24846a00  26240010
> [    4.080686]
> [    4.082517] ---[ end trace 22a8edb41f5f983b ]---
> [    4.087374] Kernel panic - not syncing: Fatal exception
> [    4.092753] Rebooting in 1 seconds..
> 
> Because the bootloader (CFE) is not initializing the Read-ahead cache properly
> on the second thread (TP1). Since the RAC was not initialized properly, we
> should avoid flushing it at the risk of corrupting the instruction stream as
> seen in the trace above.
> 
> Signed-off-by: Álvaro Fernández Rojas <noltari@...il.com>

Third time is a charm, Thomas, I believe this deserves adding a:

Fixes: d59098a0e9cb ("MIPS: bmips: use generic dma noncoherent ops")

such that this backports cleanly. Thanks!
-- 
Florian