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MIPS: add support for buggy MT7621S core detection
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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).

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>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
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Ilya Lipnitskiy authored and Thomas Bogendoerfer committed Apr 12, 2021
1 parent e607ff6 commit 6decd1a
Showing 1 changed file with 22 additions and 1 deletion.
23 changes: 22 additions & 1 deletion arch/mips/include/asm/mips-cps.h
Original file line number Diff line number Diff line change
Expand Up @@ -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");

Expand Down Expand Up @@ -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;
}

/**
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