[PATCH v2 7/9] crypto: ccp: Add support for ringing a platform doorbell

[Mario Limonciello <mario.limonciello@amd.com>]

Some platforms support using a doorbell to communicate. Export
this feature for other drivers to utilize as well.

Link: https://lore.kernel.org/linux-i2c/20220916131854.687371-3-jsd@semihalf.com/
Suggested-by: Jan Dabros <jsd@semihalf.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v1->v2:
 * New patch
---
 drivers/crypto/ccp/platform-access.c | 47 ++++++++++++++++++++++++++++
 drivers/crypto/ccp/sp-dev.h          |  1 +
 include/linux/psp-platform-access.h  | 15 +++++++++
 include/linux/psp.h                  |  3 ++
 4 files changed, 66 insertions(+)

diff --git a/drivers/crypto/ccp/platform-access.c b/drivers/crypto/ccp/platform-access.c
index af3a1e97abfe..0763389a2814 100644
--- a/drivers/crypto/ccp/platform-access.c
+++ b/drivers/crypto/ccp/platform-access.c
@@ -135,6 +135,53 @@ int psp_send_platform_access_msg(enum psp_platform_access_msg msg,
 }
 EXPORT_SYMBOL_GPL(psp_send_platform_access_msg);
 
+int psp_ring_platform_doorbell(enum psp_platform_access_msg msg)
+{
+	struct psp_device *psp = psp_get_master_device();
+	struct psp_platform_access_device *pa_dev;
+	u32 __iomem *drbl;
+	u32 drbl_reg;
+	int ret;
+
+	if (!psp || !psp->platform_access_data)
+		return -ENODEV;
+
+	pa_dev = psp->platform_access_data;
+	drbl = psp->io_regs + pa_dev->vdata->doorbell_reg;
+
+	if (!drbl)
+		return -ENODEV;
+
+	mutex_lock(&pa_dev->mutex);
+
+	if (check_recovery(drbl)) {
+		dev_dbg(psp->dev, "in recovery\n");
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	if (wait_cmd(drbl)) {
+		dev_dbg(psp->dev, "not done processing command\n");
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	drbl_reg = FIELD_PREP(PSP_DRBL_MSG, msg) | PSP_DRBL_RING;
+	iowrite32(drbl_reg, drbl);
+
+	if (wait_cmd(drbl)) {
+		ret = -ETIMEDOUT;
+		goto unlock;
+	}
+
+	ret = 0;
+unlock:
+	mutex_unlock(&pa_dev->mutex);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(psp_ring_platform_doorbell);
+
 void platform_access_dev_destroy(struct psp_device *psp)
 {
 	struct psp_platform_access_device *pa_dev = psp->platform_access_data;
diff --git a/drivers/crypto/ccp/sp-dev.h b/drivers/crypto/ccp/sp-dev.h
index 5ec6c219a731..87c0b9350bc2 100644
--- a/drivers/crypto/ccp/sp-dev.h
+++ b/drivers/crypto/ccp/sp-dev.h
@@ -54,6 +54,7 @@ struct tee_vdata {
 };
 
 struct platform_access_vdata {
+	const unsigned int doorbell_reg;
 	const unsigned int cmdresp_reg;
 	const unsigned int cmdbuff_addr_lo_reg;
 	const unsigned int cmdbuff_addr_hi_reg;
diff --git a/include/linux/psp-platform-access.h b/include/linux/psp-platform-access.h
index f5a03cd11f10..1e1d0e077cec 100644
--- a/include/linux/psp-platform-access.h
+++ b/include/linux/psp-platform-access.h
@@ -35,6 +35,21 @@ struct psp_request {
  */
 int psp_send_platform_access_msg(enum psp_platform_access_msg, struct psp_request *req);
 
+/**
+ * psp_ring_platform_doorbell() - Ring platform doorbell
+ *
+ * This function is intended to be used by drivers outside of ccp to ring the
+ * platform doorbell with a message.
+ *
+ * Returns:
+ *  0:           success
+ *  -%EBUSY:     mailbox in recovery or in use
+ *  -%ENODEV:    driver not bound with PSP device
+ *  -%ETIMEDOUT: request timed out
+ *  -%EIO:       unknown error (see kernel log)
+ */
+int psp_ring_platform_doorbell(enum psp_platform_access_msg);
+
 /**
  * psp_check_platform_access_status() - Checks whether platform features is ready
  *
diff --git a/include/linux/psp.h b/include/linux/psp.h
index d3424790a70e..92e60aeef21e 100644
--- a/include/linux/psp.h
+++ b/include/linux/psp.h
@@ -23,4 +23,7 @@
 #define PSP_CMDRESP_RECOVERY	BIT(30)
 #define PSP_CMDRESP_RESP	BIT(31)
 
+#define PSP_DRBL_MSG		PSP_CMDRESP_CMD
+#define PSP_DRBL_RING		BIT(0)
+
 #endif /* __PSP_H */
-- 
2.34.1