This patch fixes a bug introduced by:
commit c05199e5a57a579fea1e8fa65e2b511ceb524ffc
Author: Kan Liang <[email protected]>
Date: Tue Jan 20 04:54:25 2015 +0000
perf/x86/intel/uncore: Move uncore_box_init() out of driver initialization
It moves uncore_box_init() out of place but this meant that for desktop memory
controller (IMC) PCI-based PMU, the intialization was now missing causing a
crash at first access. This patch fixes the issue by adding the call to the
uncore_enable_box() in snb_uncore_imc_read_counter() to ensure the box
is initialized and the PCI BAR is io-remapped.
Signed-off-by: Stephane Eranian <[email protected]>
--
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore_snb.c
b/arch/x86/kernel/cpu/perf_event_intel_uncore_snb.c
index 4562e9e..755ec05 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore_snb.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore_snb.c
@@ -329,6 +329,9 @@ static void snb_uncore_imc_event_start(struct perf_event
*event, int flags)
list_add_tail(&event->active_entry, &box->active_list);
+ if (box->n_active == 1)
+ uncore_enable_box(box);
+
count = snb_uncore_imc_read_counter(box, event);
local64_set(&event->hw.prev_count, count);
--
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