i2c: designware: Add doorbell support for Mendocino

Mendocino and later platform don't use the platform feature mailbox for
communication for I2C arbitration, they rely upon ringing a doorbell.

Detect the platform by the device ID of the root port and choose the
appropriate method.

Link: https://lore.kernel.org/linux-i2c/20220916131854.687371-3-jsd@semihalf.com/
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: Mark Hasemeyer <markhas@chromium.org>
Tested-by: Mark Hasemeyer <markhas@chromium.org>
Acked-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: superm1

drivers/i2c/busses/Kconfig

@@ -568,6 +568,7 @@ config I2C_DESIGNWARE_AMDPSP
 	bool "AMD PSP I2C semaphore support"
 	depends on ACPI
 	depends on CRYPTO_DEV_SP_PSP
+	depends on PCI
 	depends on I2C_DESIGNWARE_PLATFORM
 	depends on (I2C_DESIGNWARE_PLATFORM=y && CRYPTO_DEV_CCP_DD=y) || \
 		   (I2C_DESIGNWARE_PLATFORM=m && CRYPTO_DEV_CCP_DD)

drivers/i2c/busses/i2c-designware-amdpsp.c

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/i2c.h>
+#include <linux/pci.h>
 #include <linux/psp-platform-access.h>
 #include <linux/psp.h>
 #include <linux/workqueue.h>
@@ -32,6 +33,8 @@ static u32 psp_i2c_access_count;
 static bool psp_i2c_mbox_fail;
 static struct device *psp_i2c_dev;
 
+static int (*_psp_send_i2c_req)(struct psp_i2c_req *req);
+
 /* Helper to verify status returned by PSP */
 static int check_i2c_req_sts(struct psp_i2c_req *req)
 {
@@ -72,6 +75,17 @@ static int psp_send_i2c_req_cezanne(struct psp_i2c_req *req)
 	return ret;
 }
 
+static int psp_send_i2c_req_doorbell(struct psp_i2c_req *req)
+{
+	int ret;
+
+	ret = psp_ring_platform_doorbell(req->type, &req->hdr.status);
+	if (ret == -EIO)
+		return check_i2c_req_sts(req);
+
+	return ret;
+}
+
 static int psp_send_i2c_req(enum psp_i2c_req_type i2c_req_type)
 {
 	struct psp_i2c_req *req;
@@ -87,7 +101,7 @@ static int psp_send_i2c_req(enum psp_i2c_req_type i2c_req_type)
 	req->type = i2c_req_type;
 
 	start = jiffies;
-	ret = read_poll_timeout(psp_send_i2c_req_cezanne, status,
+	ret = read_poll_timeout(_psp_send_i2c_req, status,
 				(status != -EBUSY),
 				PSP_I2C_REQ_RETRY_DELAY_US,
 				PSP_I2C_REQ_RETRY_CNT * PSP_I2C_REQ_RETRY_DELAY_US,
@@ -262,6 +276,8 @@ static const struct i2c_lock_operations i2c_dw_psp_lock_ops = {
 
 int i2c_dw_amdpsp_probe_lock_support(struct dw_i2c_dev *dev)
 {
+	struct pci_dev *rdev;
+
 	if (!IS_REACHABLE(CONFIG_CRYPTO_DEV_CCP_DD))
 		return -ENODEV;
 
@@ -275,6 +291,14 @@ int i2c_dw_amdpsp_probe_lock_support(struct dw_i2c_dev *dev)
 	if (psp_i2c_dev)
 		return -EEXIST;
 
+	/* Cezanne uses platform mailbox, Mendocino and later use doorbell */
+	rdev = pci_get_domain_bus_and_slot(0, 0, PCI_DEVFN(0, 0));
+	if (rdev->device == 0x1630)
+		_psp_send_i2c_req = psp_send_i2c_req_cezanne;
+	else
+		_psp_send_i2c_req = psp_send_i2c_req_doorbell;
+	pci_dev_put(rdev);
+
 	if (psp_check_platform_access_status())
 		return -EPROBE_DEFER;