x86/platform/intel-mid: Retrofit pci_platform_pm_ops ->get_state hook

Commit cc7cc02bad ("PCI: Query platform firmware for device power
state") augmented struct pci_platform_pm_ops with a ->get_state hook and
implemented it for acpi_pci_platform_pm, the only pci_platform_pm_ops
existing till v4.7.

However v4.8 introduced another pci_platform_pm_ops for Intel Mobile
Internet Devices with commit 5823d0893e ("x86/platform/intel-mid: Add
Power Management Unit driver").  It is missing the ->get_state hook,
which is fatal since pci_set_platform_pm() enforces its presence.  Andy
Shevchenko reports that without the present commit, such a device
"crashes without even a character printed out on serial console and
reboots (since watchdog)".

Retrofit mid_pci_platform_pm with the missing callback to fix the
breakage.

Acked-and-tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Fixes: cc7cc02bad ("PCI: Query platform firmware for device power state")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: linux-pci@vger.kernel.org
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: http://lkml.kernel.org/r/7c1567d4c49303a4aada94ba16275cbf56b8976b.1477221514.git.lukas@wunner.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/include/asm/intel-mid.h

@@ -17,6 +17,7 @@
 
 extern int intel_mid_pci_init(void);
 extern int intel_mid_pci_set_power_state(struct pci_dev *pdev, pci_power_t state);
+extern pci_power_t intel_mid_pci_get_power_state(struct pci_dev *pdev);
 
 extern void intel_mid_pwr_power_off(void);
 

arch/x86/platform/intel-mid/pwr.c

@@ -272,6 +272,25 @@ int intel_mid_pci_set_power_state(struct pci_dev *pdev, pci_power_t state)
 }
 EXPORT_SYMBOL_GPL(intel_mid_pci_set_power_state);
 
+pci_power_t intel_mid_pci_get_power_state(struct pci_dev *pdev)
+{
+	struct mid_pwr *pwr = midpwr;
+	int id, reg, bit;
+	u32 power;
+
+	if (!pwr || !pwr->available)
+		return PCI_UNKNOWN;
+
+	id = intel_mid_pwr_get_lss_id(pdev);
+	if (id < 0)
+		return PCI_UNKNOWN;
+
+	reg = (id * LSS_PWS_BITS) / 32;
+	bit = (id * LSS_PWS_BITS) % 32;
+	power = mid_pwr_get_state(pwr, reg);
+	return (__force pci_power_t)((power >> bit) & 3);
+}
+
 void intel_mid_pwr_power_off(void)
 {
 	struct mid_pwr *pwr = midpwr;

drivers/pci/pci-mid.c

@@ -29,6 +29,11 @@ static int mid_pci_set_power_state(struct pci_dev *pdev, pci_power_t state)
 	return intel_mid_pci_set_power_state(pdev, state);
 }
 
+static pci_power_t mid_pci_get_power_state(struct pci_dev *pdev)
+{
+	return intel_mid_pci_get_power_state(pdev);
+}
+
 static pci_power_t mid_pci_choose_state(struct pci_dev *pdev)
 {
 	return PCI_D3hot;
@@ -52,6 +57,7 @@ static bool mid_pci_need_resume(struct pci_dev *dev)
 static struct pci_platform_pm_ops mid_pci_platform_pm = {
 	.is_manageable	= mid_pci_power_manageable,
 	.set_state	= mid_pci_set_power_state,
+	.get_state	= mid_pci_get_power_state,
 	.choose_state	= mid_pci_choose_state,
 	.sleep_wake	= mid_pci_sleep_wake,
 	.run_wake	= mid_pci_run_wake,