[PATCH] spi: acpi: only look up the IRQ of confirmed SPI devices

[PATCH] spi: acpi: only look up the IRQ of confirmed SPI devices

[Rosen Penev]

When an SPI controller is registered, acpi_register_spi_device() is
called for every present ACPI device in the namespace and
acpi_spi_device_alloc() walks each device's _CRS. While doing so,
acpi_spi_add_resource() converts the first interrupt resource it finds,
even for devices that have no SpiSerialBus resource at all and are
discarded right afterwards. Converting an interrupt resource registers
its GSI, so this maps IRQs for arbitrary unrelated ACPI devices.

On a Dell Precision M4800 (Lynx Point, 24-pin IOAPIC) the DSDT reports
Haswell-ULT LPSS child devices (\_SB.PCI0.I2C0.ACD0 and
\_SB.PCI0.SDHC.WI01) as present with interrupts on GSI 37 and 38.
Registering the intel-spi controller then results in:

  ERROR: Unable to locate IOAPIC for GSI 37
  ERROR: Unable to locate IOAPIC for GSI 38

Do what the I2C core does and only parse the interrupt resource once the
device has been identified as an SPI device on this controller.

Fixes: 4c3c59544f33 ("spi/acpi: enumerate all SPI slaves in the namespace")
Signed-off-by: Rosen Penev <rosenp@gmail.com>
---
 drivers/spi/spi.c | 36 ++++++++++++++++++++++++++++--------
 1 file changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 40cda0037ea5..5a2cbebfabc5 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2995,7 +2995,6 @@ struct acpi_spi_lookup {
 	acpi_handle		device_handle;
 	u32			max_speed_hz;
 	u32			mode;
-	int			irq;
 	u8			bits_per_word;
 	u8			chip_select;
 	int			n;
@@ -3138,17 +3137,25 @@ static int acpi_spi_add_resource(struct acpi_resource *ares, void *data)
 			if (sb->device_polarity == ACPI_SPI_ACTIVE_HIGH)
 				lookup->mode |= SPI_CS_HIGH;
 		}
-	} else if (lookup->irq < 0) {
-		struct resource r;
-
-		if (acpi_dev_resource_interrupt(ares, 0, &r))
-			lookup->irq = r.start;
 	}
 
 	/* Always tell the ACPI core to skip this resource */
 	return 1;
 }
 
+static int acpi_spi_add_irq_resource(struct acpi_resource *ares, void *data)
+{
+	int *irq = data;
+	struct resource r;
+
+	if (*irq < 0 && ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS &&
+	    acpi_dev_resource_interrupt(ares, 0, &r))
+		*irq = r.start;
+
+	/* Always tell the ACPI core to skip this resource */
+	return 1;
+}
+
 /**
  * acpi_spi_device_alloc - Allocate a spi device, and fill it in with ACPI information
  * @ctlr: controller to which the spi device belongs
@@ -3173,6 +3180,7 @@ struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
 	struct list_head resource_list;
 	struct acpi_spi_lookup lookup = {};
 	struct spi_device *spi;
+	int irq = -1;
 	int ret;
 
 	if (!ctlr && index == -1)
@@ -3180,7 +3188,6 @@ struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
 
 	lookup.ctlr		= ctlr;
 	lookup.device_handle	= acpi_device_handle(adev);
-	lookup.irq		= -1;
 	lookup.index		= index;
 	lookup.n		= 0;
 
@@ -3203,6 +3210,19 @@ struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
 	if (!lookup.max_speed_hz)
 		return ERR_PTR(-ENODEV);
 
+	/*
+	 * Only look up the IRQ once we know this is an SPI device for us.
+	 * Parsing an interrupt resource maps its GSI, which must not be done
+	 * for every unrelated ACPI device walked during enumeration.
+	 */
+	INIT_LIST_HEAD(&resource_list);
+	ret = acpi_dev_get_resources(adev, &resource_list,
+				     acpi_spi_add_irq_resource, &irq);
+	if (ret < 0)
+		return ERR_PTR(ret);
+
+	acpi_dev_free_resource_list(&resource_list);
+
 	spi = spi_alloc_device(lookup.ctlr);
 	if (!spi) {
 		dev_err(&lookup.ctlr->dev, "failed to allocate SPI device for %s\n",
@@ -3215,7 +3235,7 @@ struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
 	ACPI_COMPANION_SET(&spi->dev, adev);
 	spi->max_speed_hz	= lookup.max_speed_hz;
 	spi->mode		|= lookup.mode;
-	spi->irq		= lookup.irq;
+	spi->irq		= irq;
 	spi->bits_per_word	= lookup.bits_per_word;
 	/*
 	 * By default spi->chip_select[0] will hold the physical CS number,
-- 
2.56.0