ACPI / LPSS: mask the UART TX completion interrupt

Intel LPSS provides an extra TX byte counter and an extra TX
completion interrupt for some of its bus controllers.  However,
there is no use for the extra UART interrupt and it has to be
masked out during initialization.

Otherwise, if the firmware does not mask the interrupt and
the driver does not clear it, it may cause an interrupt flood
freezing the board to happen.

Add code masking that problematic interrupt to the ACPI LPSS driver.

[rjw: Changelog]
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpi_lpss.c

@@ -32,6 +32,8 @@ ACPI_MODULE_NAME("acpi_lpss");
 #define LPSS_GENERAL_LTR_MODE_SW	BIT(2)
 #define LPSS_SW_LTR			0x10
 #define LPSS_AUTO_LTR			0x14
+#define LPSS_TX_INT			0x20
+#define LPSS_TX_INT_MASK		BIT(1)
 
 struct lpss_shared_clock {
 	const char *name;
@@ -39,6 +41,8 @@ struct lpss_shared_clock {
 	struct clk *clk;
 };
 
+struct lpss_private_data;
+
 struct lpss_device_desc {
 	bool clk_required;
 	const char *clkdev_name;
@@ -46,6 +50,7 @@ struct lpss_device_desc {
 	unsigned int prv_offset;
 	bool clk_gate;
 	struct lpss_shared_clock *shared_clock;
+	void (*setup)(struct lpss_private_data *pdata);
 };
 
 static struct lpss_device_desc lpss_dma_desc = {
@@ -60,6 +65,15 @@ struct lpss_private_data {
 	const struct lpss_device_desc *dev_desc;
 };
 
+static void lpss_uart_setup(struct lpss_private_data *pdata)
+{
+	unsigned int tx_int_offset = pdata->dev_desc->prv_offset + LPSS_TX_INT;
+	u32 reg;
+
+	reg = readl(pdata->mmio_base + tx_int_offset);
+	writel(reg | LPSS_TX_INT_MASK, pdata->mmio_base + tx_int_offset);
+}
+
 static struct lpss_device_desc lpt_dev_desc = {
 	.clk_required = true,
 	.prv_offset = 0x800,
@@ -67,6 +81,14 @@ static struct lpss_device_desc lpt_dev_desc = {
 	.clk_gate = true,
 };
 
+static struct lpss_device_desc lpt_uart_dev_desc = {
+	.clk_required = true,
+	.prv_offset = 0x800,
+	.ltr_required = true,
+	.clk_gate = true,
+	.setup = lpss_uart_setup,
+};
+
 static struct lpss_device_desc lpt_sdio_dev_desc = {
 	.prv_offset = 0x1000,
 	.ltr_required = true,
@@ -82,6 +104,7 @@ static struct lpss_device_desc byt_uart_dev_desc = {
 	.prv_offset = 0x800,
 	.clk_gate = true,
 	.shared_clock = &uart_clock,
+	.setup = lpss_uart_setup,
 };
 
 static struct lpss_shared_clock spi_clock = {
@@ -120,8 +143,8 @@ static const struct acpi_device_id acpi_lpss_device_ids[] = {
 	{ "INT33C1", (unsigned long)&lpt_dev_desc },
 	{ "INT33C2", (unsigned long)&lpt_dev_desc },
 	{ "INT33C3", (unsigned long)&lpt_dev_desc },
-	{ "INT33C4", (unsigned long)&lpt_dev_desc },
-	{ "INT33C5", (unsigned long)&lpt_dev_desc },
+	{ "INT33C4", (unsigned long)&lpt_uart_dev_desc },
+	{ "INT33C5", (unsigned long)&lpt_uart_dev_desc },
 	{ "INT33C6", (unsigned long)&lpt_sdio_dev_desc },
 	{ "INT33C7", },
 
@@ -247,6 +270,9 @@ static int acpi_lpss_create_device(struct acpi_device *adev,
 		}
 	}
 
+	if (dev_desc->setup)
+		dev_desc->setup(pdata);
+
 	adev->driver_data = pdata;
 	ret = acpi_create_platform_device(adev, id);
 	if (ret > 0)