IPS driver: verify BIOS provided limits

They're optional.  If not present or sane, we should use the CPU
defaults.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Matthew Garrett <mjg@redhat.com>

drivers/platform/x86/intel_ips.c

@@ -664,6 +664,27 @@ static bool mch_exceeded(struct ips_driver *ips)
 	return ret;
 }
 
+/**
+ * verify_limits - verify BIOS provided limits
+ * @ips: IPS structure
+ *
+ * BIOS can optionally provide non-default limits for power and temp.  Check
+ * them here and use the defaults if the BIOS values are not provided or
+ * are otherwise unusable.
+ */
+static void verify_limits(struct ips_driver *ips)
+{
+	if (ips->mcp_power_limit < ips->limits->mcp_power_limit ||
+	    ips->mcp_power_limit > 35000)
+		ips->mcp_power_limit = ips->limits->mcp_power_limit;
+
+	if (ips->mcp_temp_limit < ips->limits->core_temp_limit ||
+	    ips->mcp_temp_limit < ips->limits->mch_temp_limit ||
+	    ips->mcp_temp_limit > 150)
+		ips->mcp_temp_limit = min(ips->limits->core_temp_limit,
+					  ips->limits->mch_temp_limit);
+}
+
 /**
  * update_turbo_limits - get various limits & settings from regs
  * @ips: IPS driver struct
@@ -688,6 +709,7 @@ static void update_turbo_limits(struct ips_driver *ips)
 	ips->mcp_temp_limit = thm_readw(THM_PTL);
 	ips->mcp_power_limit = thm_readw(THM_MPPC);
 
+	verify_limits(ips);
 	/* Ignore BIOS CPU vs GPU pref */
 }
 
@@ -1156,6 +1178,7 @@ static irqreturn_t ips_irq_handler(int irq, void *arg)
 				STS_PTL_SHIFT;
 			ips->mcp_power_limit = (tc1 & STS_PPL_MASK) >>
 				STS_PPL_SHIFT;
+			verify_limits(ips);
 			spin_unlock(&ips->turbo_status_lock);
 
 			thm_writeb(THM_SEC, SEC_ACK);