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Re: [PATCH 2/2] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_C

To: "Jayachandran C." <jchandra@broadcom.com>
Subject: Re: [PATCH 2/2] MIPS: mm: Use scratch for PGD when !CONFIG_MIPS_PGD_C0_CONTEXT
From: Hauke Mehrtens <hauke@hauke-m.de>
Date: Wed, 25 Sep 2013 10:25:13 +0200
Cc: ralf@linux-mips.org, linux-mips@linux-mips.org
In-reply-to: <20130925052634.GH24359@jayachandranc.netlogicmicro.com>
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References: <1376221217-9335-1-git-send-email-jchandra@broadcom.com> <1376221217-9335-3-git-send-email-jchandra@broadcom.com> <524208F7.5060503@hauke-m.de> <20130925052634.GH24359@jayachandranc.netlogicmicro.com>
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On 09/25/2013 07:26 AM, Jayachandran C. wrote:
> On Tue, Sep 24, 2013 at 11:49:43PM +0200, Hauke Mehrtens wrote:
>> On 08/11/2013 01:40 PM, Jayachandran C wrote:
>>> Allow usage of scratch register for current pgd even when
>>> MIPS_PGD_C0_CONTEXT is not configured. MIPS_PGD_C0_CONTEXT is set
>>> for 64r2 platforms to indicate availability of Xcontext for saving
>>> cpuid, thus freeing Context to be used for saving PGD. This option
>>> was also tied to using a scratch register for storing PGD.
>>>
>>> This commit will allow usage of scratch register to store the current
>>> pgd if one can be allocated for the platform, even when
>>> MIPS_PGD_C0_CONTEXT is not set. The cpuid will be kept in the CP0
>>> Context register in this case.
>>>
>>> The code to store the current pgd for the TLB miss handler is now
>>> generated in all cases. When scratch register is available, the PGD
>>> is also stored in the scratch register.
>>>
>>> Signed-off-by: Jayachandran C <jchandra@broadcom.com>
>>
>> This patch breaks booting for me on bcm47xx. I found this commit by
>> bisecting and then reverted it and it made bcm47xx boot again. The boot
>> process stops after: [    0.000000] Inode-cache hash table entries: 4096
>> (order: 2, 16384 bytes)
>>
>> The next message would be: [    0.000000] Writing ErrCtl register=00000000
>>
>> This issue was seen on bcm4716.
>>
>> This is the boot log:
>>
>> CFE> boot -tftp -elf
>> 192.168.1.195:/brcm47xx/openwrt-brcm47xx-vmlinux-initramfs.elf
>> Loader:elf Filesys:tftp Dev:eth0
>> File:192.168.1.195:/brcm47xx/openwrt-brcm47xx-vmlinux-initramfs.elf
>> Options:(null)
>> Loading: 0x80001000/4593328 0x804626b0/279760 Entry at 0x80264800
>> Closing network.
>> Starting program at 0x80264800
>> [    0.000000] Linux version 3.12.0-rc1+ (hauke@hauke-desktop) (gcc
>> version 4.6.4 (OpenWrt/Linaro GCC 4.6-2013.05 r37948) ) #151 Tue Sep 24
>> 23:35:35 CEST 2013
>> [    0.000000] bootconsole [early0] enabled
>> [    0.000000] CPU revision is: 00019740 (MIPS 74Kc)
>> [    0.000000] bcm47xx: using bcma bus
>> [    0.000000] bcma: bus0: Found chip with id 0x4716, rev 0x01 and
>> package 0x0A
>> [    0.000000] bcma: bus0: Core 0 found: ChipCommon (manuf 0x4BF, id
>> 0x800, rev 0x1F, class 0x0)
>> [    0.000000] bcma: bus0: Core 3 found: MIPS 74K (manuf 0x4A7, id
>> 0x82C, rev 0x01, class 0x0)
>> [    0.000000] bcma: bus0: Found M25P64 serial flash (size: 8192KiB,
>> blocksize: 0x10000, blocks: 128)
>> [    0.000000] bcma: bus0: Early bus registered
>> [    0.000000] MIPS: machine is Netgear WNDR3400 V1
>> [    0.000000] Determined physical RAM map:
>> [    0.000000]  memory: 04000000 @ 00000000 (usable)
>> [    0.000000] Initrd not found or empty - disabling initrd
>> [    0.000000] Zone ranges:
>> [    0.000000]   Normal   [mem 0x00000000-0x03ffffff]
>> [    0.000000] Movable zone start for each node
>> [    0.000000] Early memory node ranges
>> [    0.000000]   node   0: [mem 0x00000000-0x03ffffff]
>> [    0.000000] Primary instruction cache 32kB, VIPT, 4-way, linesize 32
>> bytes.
>> [    0.000000] Primary data cache 32kB, 4-way, VIPT, cache aliases,
>> linesize 32 bytes
>> [    0.000000] Built 1 zonelists in Zone order, mobility grouping on.
>> Total pages: 16256
>> [    0.000000] Kernel command line:  noinitrd console=ttyS0,115200
>> [    0.000000] PID hash table entries: 256 (order: -2, 1024 bytes)
>> [    0.000000] Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)
>> [    0.000000] Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
> 
> Can you please try the attached patch? This patch was made for a slightly
> older tlbex.c, and seems to have missed this.

Thanks, this patch fixes my problem, could you please summit it for
inclusion in upstream-sfr.

Hauke


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