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ralink: fix rcu_sched stalls on mt7621

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there were 2 bugs
*) core1 came up with a bad bogo mips, looks like the clock needed time to stabilize
*) HPT frequency was not set making r4k timers not come up properly

Backport of 9551d91b1d6 "ralink: fix rcu_sched stalls on mt7621".

Signed-off-by: John Crispin <john@phrozen.org>
This commit is contained in:
John Crispin 2017-08-01 06:53:38 +02:00
parent c407e6c2f2
commit 6f4a903533
1 changed files with 98 additions and 0 deletions
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98
target/linux/ramips/patches-4.4/101-mt7621-timer.patch Normal file
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@ -0,0 +1,98 @@
--- a/arch/mips/ralink/mt7621.c
+++ b/arch/mips/ralink/mt7621.c
@@ -18,6 +18,7 @@
#include <asm/mach-ralink/ralink_regs.h>
#include <asm/mach-ralink/mt7621.h>
#include <asm/mips-boards/launch.h>
+#include <asm/delay.h>
#include <pinmux.h>
@@ -179,6 +180,58 @@ bool plat_cpu_core_present(int core)
return true;
}
+#define LPS_PREC 8
+/*
+* Re-calibration lpj(loop-per-jiffy).
+* (derived from kernel/calibrate.c)
+*/
+static int udelay_recal(void)
+{
+ unsigned int i, lpj = 0;
+ unsigned long ticks, loopbit;
+ int lps_precision = LPS_PREC;
+
+ lpj = (1<<12);
+
+ while ((lpj <<= 1) != 0) {
+ /* wait for "start of" clock tick */
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+
+ /* Go .. */
+ ticks = jiffies;
+ __delay(lpj);
+ ticks = jiffies - ticks;
+ if (ticks)
+ break;
+ }
+
+ /*
+ * Do a binary approximation to get lpj set to
+ * equal one clock (up to lps_precision bits)
+ */
+ lpj >>= 1;
+ loopbit = lpj;
+ while (lps_precision-- && (loopbit >>= 1)) {
+ lpj |= loopbit;
+ ticks = jiffies;
+ while (ticks == jiffies)
+ /* nothing */;
+ ticks = jiffies;
+ __delay(lpj);
+ if (jiffies != ticks) /* longer than 1 tick */
+ lpj &= ~loopbit;
+ }
+ printk(KERN_INFO "%d CPUs re-calibrate udelay(lpj = %d)\n", NR_CPUS, lpj);
+
+ for(i=0; i< NR_CPUS; i++)
+ cpu_data[i].udelay_val = lpj;
+
+ return 0;
+}
+device_initcall(udelay_recal);
+
void prom_soc_init(struct ralink_soc_info *soc_info)
{
void __iomem *sysc = (void __iomem *) KSEG1ADDR(MT7621_SYSC_BASE);
--- a/arch/mips/ralink/Kconfig
+++ b/arch/mips/ralink/Kconfig
@@ -56,6 +56,7 @@ choice
select COMMON_CLK
select CLKSRC_MIPS_GIC
select HW_HAS_PCI
+ select GENERIC_CLOCKEVENTS_BROADCAST
endchoice
choice
--- a/arch/mips/ralink/timer-gic.c
+++ b/arch/mips/ralink/timer-gic.c
@@ -12,6 +12,7 @@
#include <linux/of.h>
#include <linux/clk-provider.h>
#include <linux/clocksource.h>
+#include <asm/time.h>
#include "common.h"
@@ -19,6 +20,8 @@ void __init plat_time_init(void)
{
ralink_of_remap();
+ mips_hpt_frequency = 880000000 / 2;
+
of_clk_init(NULL);
clocksource_probe();
}