Re: [PATCH v3] MIPS: add support for buggy MT7621S core detection

Greg Ungerer
2021-09-16T06:54:32Z

Hi Sergio,

On 16/9/21 4:33 pm, Sergio Paracuellos wrote:
> On Thu, Sep 16, 2021 at 4:57 AM Greg Ungerer <gerg@kernel.org> wrote:
>>
>> Hi Ilya,
>>
>>> Most MT7621 SoCs have 2 cores, which is detected and supported properly
>>> by CPS.
>>>
>>> Unfortunately, MT7621 SoC has a less common S variant with only one core.
>>> On MT7621S, GCR_CONFIG still reports 2 cores, which leads to hangs when
>>> starting SMP. CPULAUNCH registers can be used in that case to detect the
>>> absence of the second core and override the GCR_CONFIG PCORES field.
>>>
>>> Rework a long-standing OpenWrt patch to override the value of
>>> mips_cps_numcores on single-core MT7621 systems.
>>>
>>> Tested on a dual-core MT7621 device (Ubiquiti ER-X) and a single-core
>>> MT7621 device (Netgear R6220).
>>
>> This is breaking core detection on my MT7621 based platforms.
>> I only get 2 cores detected now running 5.13. Reverting this change gives
>> me 4 cores back.
>
> I also have a 4 core mt7621 based board and this patch change does not
> have problems for me. Let me know if you need me to check something
> from my board.
>
> I noticed that on boot the following message appears and might be
> related with the way used here to make the core number detection:
>
> [ 0.000000] VPE topology {2,2} total 4
>
> Is this the same for your board?

When booting with this patch applied I get:

VPE topology {2} total 2

with patch reverted I get:

VPE topology {2,2} total 4

Regards
Greg

> Best regards,
> Sergio Paracuellos
>
>>
>> From a fully working (pre-change) system I get:
>>
>> # cat /proc/cpuinfo
>> system type : MediaTek MT7621 ver:1 eco:3
>> machine : Digi EX15
>> processor : 0
>> cpu model : MIPS 1004Kc V2.15
>> BogoMIPS : 586.13
>> wait instruction : yes
>> microsecond timers : yes
>> tlb_entries : 32
>> extra interrupt vector : yes
>> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
>> isa : mips1 mips2 mips32r1 mips32r2
>> ASEs implemented : mips16 dsp mt
>> shadow register sets : 1
>> kscratch registers : 0
>> package : 0
>> core : 0
>> VPE : 0
>> VCED exceptions : not available
>> VCEI exceptions : not available
>>
>> processor : 1
>> cpu model : MIPS 1004Kc V2.15
>> BogoMIPS : 586.13
>> wait instruction : yes
>> microsecond timers : yes
>> tlb_entries : 32
>> extra interrupt vector : yes
>> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
>> isa : mips1 mips2 mips32r1 mips32r2
>> ASEs implemented : mips16 dsp mt
>> shadow register sets : 1
>> kscratch registers : 0
>> package : 0
>> core : 0
>> VPE : 1
>> VCED exceptions : not available
>> VCEI exceptions : not available
>>
>> processor : 2
>> cpu model : MIPS 1004Kc V2.15
>> BogoMIPS : 586.13
>> wait instruction : yes
>> microsecond timers : yes
>> tlb_entries : 32
>> extra interrupt vector : yes
>> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
>> isa : mips1 mips2 mips32r1 mips32r2
>> ASEs implemented : mips16 dsp mt
>> shadow register sets : 1
>> kscratch registers : 0
>> package : 0
>> core : 1
>> VPE : 0
>> VCED exceptions : not available
>> VCEI exceptions : not available
>>
>> processor : 3
>> cpu model : MIPS 1004Kc V2.15
>> BogoMIPS : 586.13
>> wait instruction : yes
>> microsecond timers : yes
>> tlb_entries : 32
>> extra interrupt vector : yes
>> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
>> isa : mips1 mips2 mips32r1 mips32r2
>> ASEs implemented : mips16 dsp mt
>> shadow register sets : 1
>> kscratch registers : 0
>> package : 0
>> core : 1
>> VPE : 1
>> VCED exceptions : not available
>> VCEI exceptions : not available
>>
>>
>> After this patch is applied:
>>
>> # cat /proc/cpuinfo
>> system type : MediaTek MT7621 ver:1 eco:3
>> machine : Digi EX15
>> processor : 0
>> cpu model : MIPS 1004Kc V2.15
>> BogoMIPS : 586.13
>> wait instruction : yes
>> microsecond timers : yes
>> tlb_entries : 32
>> extra interrupt vector : yes
>> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
>> isa : mips1 mips2 mips32r1 mips32r2
>> ASEs implemented : mips16 dsp mt
>> shadow register sets : 1
>> kscratch registers : 0
>> package : 0
>> core : 0
>> VPE : 0
>> VCED exceptions : not available
>> VCEI exceptions : not available
>>
>> processor : 1
>> cpu model : MIPS 1004Kc V2.15
>> BogoMIPS : 586.13
>> wait instruction : yes
>> microsecond timers : yes
>> tlb_entries : 32
>> extra interrupt vector : yes
>> hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
>> isa : mips1 mips2 mips32r1 mips32r2
>> ASEs implemented : mips16 dsp mt
>> shadow register sets : 1
>> kscratch registers : 0
>> package : 0
>> core : 0
>> VPE : 1
>> VCED exceptions : not available
>> VCEI exceptions : not available
>>
>> Any ideas?
>>
>> Regards
>> Greg
>>
>>
>>> Original 4.14 OpenWrt patch:
>>> Link: https://git.openwrt.org/?p=openwrt/openwrt.git;a=commitdiff;h=4cdbc90a376dd0555201c1434a2081e055e9ceb7
>>> Current 5.10 OpenWrt patch:
>>> Link: https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob;f=target/linux/ramips/patches-5.10/320-mt7621-core-detect-hack.patch;h=c63f0f4c1ec742e24d8480e80553863744b58f6a;hb=10267e17299806f9885d086147878f6c492cb904
>>>
>>> Suggested-by: Felix Fietkau <nbd@nbd.name>
>>> Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@gmail.com>
>>> ---
>>> arch/mips/include/asm/mips-cps.h | 23 ++++++++++++++++++++++-
>>> 1 file changed, 22 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/mips/include/asm/mips-cps.h b/arch/mips/include/asm/mips-cps.h
>>> index fd43d876892e..35fb8ee6dd33 100644
>>> --- a/arch/mips/include/asm/mips-cps.h
>>> +++ b/arch/mips/include/asm/mips-cps.h
>>> @@ -10,6 +10,8 @@
>>> #include <linux/io.h>
>>> #include <linux/types.h>
>>>
>>> +#include <asm/mips-boards/launch.h>
>>> +
>>> extern unsigned long __cps_access_bad_size(void)
>>> __compiletime_error("Bad size for CPS accessor");
>>>
>>> @@ -165,11 +167,30 @@ static inline uint64_t mips_cps_cluster_config(unsigned int cluster)
>>> */
>>> static inline unsigned int mips_cps_numcores(unsigned int cluster)
>>> {
>>> + unsigned int ncores;
>>> +
>>> if (!mips_cm_present())
>>> return 0;
>>>
>>> /* Add one before masking to handle 0xff indicating no cores */
>>> - return (mips_cps_cluster_config(cluster) + 1) & CM_GCR_CONFIG_PCORES;
>>> + ncores = (mips_cps_cluster_config(cluster) + 1) & CM_GCR_CONFIG_PCORES;
>>> +
>>> + if (IS_ENABLED(CONFIG_SOC_MT7621)) {
>>> + struct cpulaunch *launch;
>>> +
>>> + /*
>>> + * Ralink MT7621S SoC is single core, but the GCR_CONFIG method
>>> + * always reports 2 cores. Check the second core's LAUNCH_FREADY
>>> + * flag to detect if the second core is missing. This method
>>> + * only works before the core has been started.
>>> + */
>>> + launch = (struct cpulaunch *)CKSEG0ADDR(CPULAUNCH);
>>> + launch += 2; /* MT7621 has 2 VPEs per core */
>>> + if (!(launch->flags & LAUNCH_FREADY))
>>> + ncores = 1;
>>> + }
>>> +
>>> + return ncores;
>>> }
>>>
>>> /**
>>> --
>>> 2.31.1
>>