intel_th: Disallow multi mode on devices where it's broken

Some versions of Intel TH have an issue that prevents the multi mode of
MSU from working correctly, resulting in no trace data and potentially
stuck MSU pipeline.

Disable multi mode on such devices.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200317062215.15598-2-alexander.shishkin@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/intel_th/intel_th.h

@@ -47,11 +47,13 @@ struct intel_th_output {
 /**
  * struct intel_th_drvdata - describes hardware capabilities and quirks
  * @tscu_enable:	device needs SW to enable time stamping unit
+ * @multi_is_broken:	device has multiblock mode is broken
  * @has_mintctl:	device has interrupt control (MINTCTL) register
  * @host_mode_only:	device can only operate in 'host debugger' mode
  */
 struct intel_th_drvdata {
 	unsigned int	tscu_enable        : 1,
+			multi_is_broken    : 1,
 			has_mintctl        : 1,
 			host_mode_only     : 1;
 };

drivers/hwtracing/intel_th/msu.c

@@ -157,7 +157,8 @@ struct msc {
 	/* config */
 	unsigned int		enabled : 1,
 				wrap	: 1,
-				do_irq	: 1;
+				do_irq	: 1,
+				multi_is_broken : 1;
 	unsigned int		mode;
 	unsigned int		burst_len;
 	unsigned int		index;
@@ -1664,7 +1665,7 @@ static int intel_th_msc_init(struct msc *msc)
 {
 	atomic_set(&msc->user_count, -1);
 
-	msc->mode = MSC_MODE_MULTI;
+	msc->mode = msc->multi_is_broken ? MSC_MODE_SINGLE : MSC_MODE_MULTI;
 	mutex_init(&msc->buf_mutex);
 	INIT_LIST_HEAD(&msc->win_list);
 	INIT_LIST_HEAD(&msc->iter_list);
@@ -1876,6 +1877,9 @@ mode_store(struct device *dev, struct device_attribute *attr, const char *buf,
 	return -EINVAL;
 
 found:
+	if (i == MSC_MODE_MULTI && msc->multi_is_broken)
+		return -EOPNOTSUPP;
+
 	mutex_lock(&msc->buf_mutex);
 	ret = 0;
 
@@ -2082,6 +2086,9 @@ static int intel_th_msc_probe(struct intel_th_device *thdev)
 	if (!res)
 		msc->do_irq = 1;
 
+	if (INTEL_TH_CAP(to_intel_th(thdev), multi_is_broken))
+		msc->multi_is_broken = 1;
+
 	msc->index = thdev->id;
 
 	msc->thdev = thdev;

drivers/hwtracing/intel_th/pci.c

@@ -120,6 +120,10 @@ static void intel_th_pci_remove(struct pci_dev *pdev)
 	pci_free_irq_vectors(pdev);
 }
 
+static const struct intel_th_drvdata intel_th_1x_multi_is_broken = {
+	.multi_is_broken	= 1,
+};
+
 static const struct intel_th_drvdata intel_th_2x = {
 	.tscu_enable	= 1,
 	.has_mintctl	= 1,
@@ -152,7 +156,7 @@ static const struct pci_device_id intel_th_pci_id_table[] = {
 	{
 		/* Kaby Lake PCH-H */
 		PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0xa2a6),
-		.driver_data = (kernel_ulong_t)0,
+		.driver_data = (kernel_ulong_t)&intel_th_1x_multi_is_broken,
 	},
 	{
 		/* Denverton */
@@ -207,7 +211,7 @@ static const struct pci_device_id intel_th_pci_id_table[] = {
 	{
 		/* Comet Lake PCH-V */
 		PCI_DEVICE(PCI_VENDOR_ID_INTEL, 0xa3a6),
-		.driver_data = (kernel_ulong_t)&intel_th_2x,
+		.driver_data = (kernel_ulong_t)&intel_th_1x_multi_is_broken,
 	},
 	{
 		/* Ice Lake NNPI */