Merge tag 'arc-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull ARC updates from Vineet Gupta:
 "Some fixes, nothing too exciting this time as well..."

* tag 'arc-3.20-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: fix page address calculation if PAGE_OFFSET != LINUX_LINK_BASE
  ARC: Fix earlycon build breakage
  ARC: Dynamically determine BASE_BAUD from DeviceTree
  arc: Remove unused prepare_to_copy()
  ARC: use ACCESS_ONCE in cmpxchg loop
  ARC: add some more comments to ret_from_fork
  ARC: fix /proc/cpuinfo for offline cpus

7 files changed, 47 insertions, 29 deletions

diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h
index ffed3b2cf313..9615fe1701c6 100644
--- a/arch/arc/include/asm/pgtable.h
+++ b/arch/arc/include/asm/pgtable.h
@@ -257,7 +257,8 @@ static inline void pmd_set(pmd_t *pmdp, pte_t *ptep)
 #define pmd_clear(xp)                   do { pmd_val(*(xp)) = 0; } while (0)
 
 #define pte_page(x) (mem_map + \
-                (unsigned long)(((pte_val(x) - PAGE_OFFSET) >> PAGE_SHIFT)))
+                (unsigned long)(((pte_val(x) - CONFIG_LINUX_LINK_BASE) >> \
+                                PAGE_SHIFT)))
 
 #define mk_pte(page, pgprot)                                            \
 ({                                                                      \
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index 210fe97464c3..4e547296831d 100644
--- a/arch/arc/include/asm/processor.h
+++ b/arch/arc/include/asm/processor.h
@@ -56,9 +56,6 @@ unsigned long thread_saved_pc(struct task_struct *t);
 /* Free all resources held by a thread */
 #define release_thread(thread) do { } while (0)
 
-/* Prepare to copy thread state - unlazy all lazy status */
-#define prepare_to_copy(tsk)    do { } while (0)
-
 /*
  * A lot of busy-wait loops in SMP are based off of non-volatile data otherwise
  * get optimised away by gcc
diff --git a/arch/arc/include/asm/serial.h b/arch/arc/include/asm/serial.h
index 602b0970a764..744a6ae15754 100644
--- a/arch/arc/include/asm/serial.h
+++ b/arch/arc/include/asm/serial.h
@@ -10,26 +10,13 @@
 #define _ASM_ARC_SERIAL_H
 
 /*
- * early-8250 requires BASE_BAUD to be defined and includes this header.
- * We put in a typical value:
- *      (core clk / 16) - i.e. UART samples 16 times per sec.
- * Athough in multi-platform-image this might not work, specially if the
- * clk driving the UART is different.
- * We can't use DeviceTree as this is typically for early serial.
+ * early 8250 (now earlycon) requires BASE_BAUD to be defined in this header.
+ * However to still determine it dynamically (for multi-platform images)
+ * we do this in a helper by parsing the FDT early
  */
 
-#include <asm/clk.h>
+extern unsigned int __init arc_early_base_baud(void);
 
-#define BASE_BAUD       (arc_get_core_freq() / 16)
-
-/*
- * This is definitely going to break early 8250 consoles on multi-platform
- * images but hey, it won't add any code complexity for a debug feature of
- * one broken driver.
- */
-#ifdef CONFIG_ARC_PLAT_TB10X
-#undef BASE_BAUD
-#define BASE_BAUD       (arc_get_core_freq() / 16 / 3)
-#endif
+#define BASE_BAUD       arc_early_base_baud()
 
 #endif /* _ASM_ARC_SERIAL_H */
diff --git a/arch/arc/kernel/devtree.c b/arch/arc/kernel/devtree.c
index fffdb5e41b20..e32b54abff51 100644
--- a/arch/arc/kernel/devtree.c
+++ b/arch/arc/kernel/devtree.c
@@ -17,6 +17,28 @@
 #include <asm/clk.h>
 #include <asm/mach_desc.h>
 
+#ifdef CONFIG_SERIAL_EARLYCON
+
+static unsigned int __initdata arc_base_baud;
+
+unsigned int __init arc_early_base_baud(void)
+{
+        return arc_base_baud/16;
+}
+
+static void __init arc_set_early_base_baud(unsigned long dt_root)
+{
+        unsigned int core_clk = arc_get_core_freq();
+
+        if (of_flat_dt_is_compatible(dt_root, "abilis,arc-tb10x"))
+                arc_base_baud = core_clk/3;
+        else
+                arc_base_baud = core_clk;
+}
+#else
+#define arc_set_early_base_baud(dt_root)
+#endif
+
 static const void * __init arch_get_next_mach(const char *const **match)
 {
         static const struct machine_desc *mdesc = __arch_info_begin;
@@ -56,5 +78,7 @@ const struct machine_desc * __init setup_machine_fdt(void *dt)
         if (clk)
                 arc_set_core_freq(of_read_ulong(clk, len/4));
 
+        arc_set_early_base_baud(dt_root);
+
         return mdesc;
 }
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 83a046a7cd06..d868289c5a26 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -736,16 +736,20 @@ ENTRY(ret_from_fork)
         ; put last task in scheduler queue
         bl   @schedule_tail
 
-        ; If kernel thread, jump to its entry-point
         ld   r9, [sp, PT_status32]
         brne r9, 0, 1f
 
-        jl.d [r14]
-        mov  r0, r13            ; arg to payload
+        jl.d [r14]              ; kernel thread entry point
+        mov  r0, r13            ; (see PF_KTHREAD block in copy_thread)
 
 1:
-        ; special case of kernel_thread entry point returning back due to
-        ; kernel_execve() - pretend return from syscall to ret to userland
+        ; Return to user space
+        ; 1. Any forked task (Reach here via BRne above)
+        ; 2. First ever init task (Reach here via return from JL above)
+        ;    This is the historic "kernel_execve" use-case, to return to init
+        ;    user mode, in a round about way since that is always done from
+        ;    a kernel thread which is executed via JL above but always returns
+        ;    out whenever kernel_execve (now inline do_fork()) is involved
         b    ret_from_exception
 END(ret_from_fork)
 
diff --git a/arch/arc/kernel/setup.c b/arch/arc/kernel/setup.c
index 252bf603db9c..900f68a70088 100644
--- a/arch/arc/kernel/setup.c
+++ b/arch/arc/kernel/setup.c
@@ -412,6 +412,11 @@ static int show_cpuinfo(struct seq_file *m, void *v)
         char *str;
         int cpu_id = ptr_to_cpu(v);
 
+        if (!cpu_online(cpu_id)) {
+                seq_printf(m, "processor [%d]\t: Offline\n", cpu_id);
+                goto done;
+        }
+
         str = (char *)__get_free_page(GFP_TEMPORARY);
         if (!str)
                 goto done;
@@ -429,7 +434,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 
         free_page((unsigned long)str);
 done:
-        seq_printf(m, "\n\n");
+        seq_printf(m, "\n");
 
         return 0;
 }
diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
index 20ebb602ea2f..6a400b1b0b62 100644
--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -221,7 +221,7 @@ static void ipi_send_msg_one(int cpu, enum ipi_msg_type msg)
          * and read back old value
          */
         do {
-                new = old = *ipi_data_ptr;
+                new = old = ACCESS_ONCE(*ipi_data_ptr);
                 new |= 1U << msg;
         } while (cmpxchg(ipi_data_ptr, old, new) != old);