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 <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/hwtracing/intel_th/intel_th.h

···
 /**
  * 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

···
 	/* 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;
···
 {
 	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);
···
 	return -EINVAL;
 
 found:
+	if (i == MSC_MODE_MULTI && msc->multi_is_broken)
+		return -EOPNOTSUPP;
+
 	mutex_lock(&msc->buf_mutex);
 	ret = 0;
 
···
 	res = intel_th_device_get_resource(thdev, IORESOURCE_IRQ, 1);
 	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;
 

drivers/hwtracing/intel_th/pci.c

···
 	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,
···
 	{
 		/* 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 */
···
 	{
 		/* 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 */