[POWERPC] cell: Support pinhole-reset on IBM cell blades

The Cell Broadband Engine has a method of injecting a
system-reset-exception from an external source into the
operating system, which should trigger the regular behaviour
of entering xmon or kdump.

Unfortunately, the exception handler cannot distinguish it from
other interrupt causes by the SRR1 register, which gets used
for this on Power 6 and others.

IBM Blade servers that want to support triggering the
system reset exception using a pinhole button in the front
panel therefore use an extra register to determine the
reset cause.

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

--
Signed-off-by: Paul Mackerras <paulus@samba.org>

2 files changed, 32 insertions, 2 deletions

diff --git a/arch/powerpc/platforms/cell/cbe_regs.h b/arch/powerpc/platforms/cell/cbe_regs.h
index 17d597144877..b24025f2ac7a 100644
--- a/arch/powerpc/platforms/cell/cbe_regs.h
+++ b/arch/powerpc/platforms/cell/cbe_regs.h
@@ -113,10 +113,14 @@ struct cbe_pmd_regs {
         u64     checkstop_fir;                                  /* 0x0c00 */
         u64     recoverable_fir;                                /* 0x0c08 */
         u64     spec_att_mchk_fir;                              /* 0x0c10 */
-        u64     fir_mode_reg;                                   /* 0x0c18 */
+        u32     fir_mode_reg;                                   /* 0x0c18 */
+        u8      pad_0x0c1c_0x0c20 [4];                          /* 0x0c1c */
+#define CBE_PMD_FIR_MODE_M8             0x00800
         u64     fir_enable_mask;                                /* 0x0c20 */
 
-        u8      pad_0x0c28_0x1000 [0x1000 - 0x0c28];            /* 0x0c28 */
+        u8      pad_0x0c28_0x0ca8 [0x0ca8 - 0x0c28];            /* 0x0c28 */
+        u64     ras_esc_0;                                      /* 0x0ca8 */
+        u8      pad_0x0cb0_0x1000 [0x1000 - 0x0cb0];            /* 0x0cb0 */
 };
 
 extern struct cbe_pmd_regs __iomem *cbe_get_pmd_regs(struct device_node *np);
diff --git a/arch/powerpc/platforms/cell/pervasive.c b/arch/powerpc/platforms/cell/pervasive.c
index 812bf563ed65..4ede22d363fa 100644
--- a/arch/powerpc/platforms/cell/pervasive.c
+++ b/arch/powerpc/platforms/cell/pervasive.c
@@ -38,6 +38,8 @@
 #include "pervasive.h"
 #include "cbe_regs.h"
 
+static int sysreset_hack;
+
 static void cbe_power_save(void)
 {
         unsigned long ctrl, thread_switch_control;
@@ -85,6 +87,9 @@ static void cbe_power_save(void)
 
 static int cbe_system_reset_exception(struct pt_regs *regs)
 {
+        int cpu;
+        struct cbe_pmd_regs __iomem *pmd;
+
         switch (regs->msr & SRR1_WAKEMASK) {
         case SRR1_WAKEEE:
                 do_IRQ(regs);
@@ -93,6 +98,18 @@ static int cbe_system_reset_exception(struct pt_regs *regs)
                 timer_interrupt(regs);
                 break;
         case SRR1_WAKEMT:
+                /*
+                 * The BMC can inject user triggered system reset exceptions,
+                 * but cannot set the system reset reason in srr1,
+                 * so check an extra register here.
+                 */
+                if (sysreset_hack && (cpu = smp_processor_id()) == 0) {
+                        pmd = cbe_get_cpu_pmd_regs(cpu);
+                        if (in_be64(&pmd->ras_esc_0) & 0xffff) {
+                                out_be64(&pmd->ras_esc_0, 0);
+                                return 0;
+                        }
+                }
                 break;
 #ifdef CONFIG_CBE_RAS
         case SRR1_WAKESYSERR:
@@ -113,9 +130,12 @@ static int cbe_system_reset_exception(struct pt_regs *regs)
 void __init cbe_pervasive_init(void)
 {
         int cpu;
+
         if (!cpu_has_feature(CPU_FTR_PAUSE_ZERO))
                 return;
 
+        sysreset_hack = machine_is_compatible("IBM,CBPLUS-1.0");
+
         for_each_possible_cpu(cpu) {
                 struct cbe_pmd_regs __iomem *regs = cbe_get_cpu_pmd_regs(cpu);
                 if (!regs)
@@ -124,6 +144,12 @@ void __init cbe_pervasive_init(void)
                  /* Enable Pause(0) control bit */
                 out_be64(&regs->pmcr, in_be64(&regs->pmcr) |
                                             CBE_PMD_PAUSE_ZERO_CONTROL);
+
+                /* Enable JTAG system-reset hack */
+                if (sysreset_hack)
+                        out_be32(&regs->fir_mode_reg,
+                                in_be32(&regs->fir_mode_reg) |
+                                CBE_PMD_FIR_MODE_M8);
         }
 
         ppc_md.power_save = cbe_power_save;