[PATCH V2] ACPI / LPSS: Add device link for CHT SD card dependency on I2C

[Adrian Hunter]

Some Cherry Trail boards have a dependency between the SDHCI host
controller used for SD cards and an external PMIC accessed via I2C. Add a
device link between the SDHCI host controller (consumer) and the I2C
adapter (supplier).

This patch depends on a fix to devices links, namely commit 0ff26c662d5f
("driver core: Fix device link deferred probe"). And also either,
commit 126dbc6b49c8 ("PM: i2c-designware-platdrv: Clean up PM handling in
probe"), or patch "PM / runtime: Fix handling of suppliers with disabled
runtime PM".

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---


Changes in V2:

	Add a comment about why it is necessary to hardcode the links
	information in the code


 drivers/acpi/acpi_lpss.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 146 insertions(+)

diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
index 7f2b02cc8ea1..9cfe6b71078b 100644
--- a/drivers/acpi/acpi_lpss.c
+++ b/drivers/acpi/acpi_lpss.c
@@ -290,6 +290,11 @@ static void bsw_pwm_setup(struct lpss_private_data *pdata)
 	{}
 };
 
+static const struct x86_cpu_id cht_cpu[] = {
+	ICPU(INTEL_FAM6_ATOM_AIRMONT),	/* Braswell, Cherry Trail */
+	{}
+};
+
 #else
 
 #define LPSS_ADDR(desc) (0UL)
@@ -427,6 +432,146 @@ static int register_device_clock(struct acpi_device *adev,
 	return 0;
 }
 
+struct lpss_device_links {
+	const char *supplier_hid;
+	const char *supplier_uid;
+	const char *consumer_hid;
+	const char *consumer_uid;
+	const struct x86_cpu_id *cpus;
+	u32 flags;
+};
+
+/*
+ * The _DEP method is used to identify dependencies but instead of creating
+ * device links for every handle in _DEP, only links in the following list are
+ * created. That is necessary because, in the general case, _DEP can refer to
+ * devices that might not have drivers, or that are on different buses, or where
+ * the supplier is not enumerated until after the consumer is probed.
+ */
+static const struct lpss_device_links lpss_device_links[] = {
+	{"808622C1", "7", "80860F14", "3", cht_cpu, DL_FLAG_PM_RUNTIME},
+};
+
+static bool hid_uid_match(const char *hid1, const char *uid1,
+			  const char *hid2, const char *uid2)
+{
+	return !strcmp(hid1, hid2) && uid1 && uid2 && !strcmp(uid1, uid2);
+}
+
+static bool acpi_lpss_is_supplier(struct acpi_device *adev,
+				  const struct lpss_device_links *link)
+{
+	return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
+			     link->supplier_hid, link->supplier_uid);
+}
+
+static bool acpi_lpss_is_consumer(struct acpi_device *adev,
+				  const struct lpss_device_links *link)
+{
+	return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
+			     link->consumer_hid, link->consumer_uid);
+}
+
+struct hid_uid {
+	const char *hid;
+	const char *uid;
+};
+
+static int match_hid_uid(struct device *dev, void *data)
+{
+	struct acpi_device *adev = ACPI_COMPANION(dev);
+	struct hid_uid *id = data;
+
+	if (!adev)
+		return 0;
+
+	return hid_uid_match(acpi_device_hid(adev), acpi_device_uid(adev),
+			     id->hid, id->uid);
+}
+
+static struct device *acpi_lpss_find_device(const char *hid, const char *uid)
+{
+	struct hid_uid data = {
+		.hid = hid,
+		.uid = uid,
+	};
+
+	return bus_find_device(&platform_bus_type, NULL, &data, match_hid_uid);
+}
+
+static bool acpi_lpss_dep(struct acpi_device *adev, acpi_handle handle)
+{
+	struct acpi_handle_list dep_devices;
+	acpi_status status;
+	int i;
+
+	if (!acpi_has_method(adev->handle, "_DEP"))
+		return false;
+
+	status = acpi_evaluate_reference(adev->handle, "_DEP", NULL,
+					 &dep_devices);
+	if (ACPI_FAILURE(status)) {
+		dev_dbg(&adev->dev, "Failed to evaluate _DEP.\n");
+		return false;
+	}
+
+	for (i = 0; i < dep_devices.count; i++) {
+		if (dep_devices.handles[i] == handle)
+			return true;
+	}
+
+	return false;
+}
+
+static void acpi_lpss_link_consumer(struct device *dev1,
+				    const struct lpss_device_links *link)
+{
+	struct device *dev2;
+
+	dev2 = acpi_lpss_find_device(link->consumer_hid, link->consumer_uid);
+	if (!dev2)
+		return;
+
+	if (acpi_lpss_dep(ACPI_COMPANION(dev2), ACPI_HANDLE(dev1)))
+		device_link_add(dev2, dev1, link->flags);
+
+	put_device(dev2);
+}
+
+static void acpi_lpss_link_supplier(struct device *dev1,
+				    const struct lpss_device_links *link)
+{
+	struct device *dev2;
+
+	dev2 = acpi_lpss_find_device(link->supplier_hid, link->supplier_uid);
+	if (!dev2)
+		return;
+
+	if (acpi_lpss_dep(ACPI_COMPANION(dev1), ACPI_HANDLE(dev2)))
+		device_link_add(dev1, dev2, link->flags);
+
+	put_device(dev2);
+}
+
+static void acpi_lpss_create_device_links(struct acpi_device *adev,
+					  struct platform_device *pdev)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(lpss_device_links); i++) {
+		const struct lpss_device_links *link = &lpss_device_links[i];
+
+		if (link->cpus && !x86_match_cpu(link->cpus))
+			continue;
+
+		if (acpi_lpss_is_supplier(adev, link))
+			acpi_lpss_link_consumer(&pdev->dev, link);
+
+		if (acpi_lpss_is_consumer(adev, link))
+			acpi_lpss_link_supplier(&pdev->dev, link);
+	}
+}
+
 static int acpi_lpss_create_device(struct acpi_device *adev,
 				   const struct acpi_device_id *id)
 {
@@ -500,6 +645,7 @@ static int acpi_lpss_create_device(struct acpi_device *adev,
 	adev->driver_data = pdata;
 	pdev = acpi_create_platform_device(adev, dev_desc->properties);
 	if (!IS_ERR_OR_NULL(pdev)) {
+		acpi_lpss_create_device_links(adev, pdev);
 		return 1;
 	}
 
-- 
1.9.1