Re: [PATCH v3] MIPS: add support for buggy MT7621S core detection
From: Greg Ungerer
Date: Thu Sep 16 2021 - 02:54:32 EST
Hi Sergio,
On 16/9/21 4:33 pm, Sergio Paracuellos wrote:
On Thu, Sep 16, 2021 at 4:57 AM Greg Ungerer <gerg@xxxxxxxxxx> 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@xxxxxxxx>
Signed-off-by: Ilya Lipnitskiy <ilya.lipnitskiy@xxxxxxxxx>
---
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