hwmon: (coretemp) fix reading of microcode revision (v2)

According to the documentation, simply reading the respective MSR
isn't sufficient: It should be written with zeros, cpuid(1) be
executed, and then read (see arch/x86/kernel/cpu/intel.c for an
example).

v2: Fail probe when microcode revision cannot be determined, but is
needed to check for proper operation.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Chen Gong <gong.chen@linux.intel.com>
Cc: Jean Delvare <khali@linux-fr.org>
Acked-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>

1 files changed, 18 insertions, 2 deletions

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 467488c278e9..42de98d73ff5 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -289,6 +289,15 @@ static int __devinit get_tjmax(struct cpuinfo_x86 *c, u32 id,
         }
 }
 
+static void __devinit get_ucode_rev_on_cpu(void *edx)
+{
+        u32 eax;
+
+        wrmsr(MSR_IA32_UCODE_REV, 0, 0);
+        sync_core();
+        rdmsr(MSR_IA32_UCODE_REV, eax, *(u32 *)edx);
+}
+
 static int __devinit coretemp_probe(struct platform_device *pdev)
 {
         struct coretemp_data *data;
@@ -324,8 +333,15 @@ static int __devinit coretemp_probe(struct platform_device *pdev)
 
         if ((c->x86_model == 0xe) && (c->x86_mask < 0xc)) {
                 /* check for microcode update */
-                rdmsr_on_cpu(data->id, MSR_IA32_UCODE_REV, &eax, &edx);
-                if (edx < 0x39) {
+                err = smp_call_function_single(data->id, get_ucode_rev_on_cpu,
+                                               &edx, 1);
+                if (err) {
+                        dev_err(&pdev->dev,
+                                "Cannot determine microcode revision of "
+                                "CPU#%u (%d)!\n", data->id, err);
+                        err = -ENODEV;
+                        goto exit_free;
+                } else if (edx < 0x39) {
                         err = -ENODEV;
                         dev_err(&pdev->dev,
                                 "Errata AE18 not fixed, update BIOS or "