crypto: ccp - Add support for ringing a platform doorbell

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>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/ccp/platform-access.c

@@ -20,6 +20,14 @@
 
 #define PSP_CMD_TIMEOUT_US	(500 * USEC_PER_MSEC)
 
+/* Doorbell shouldn't be ringing */
+static int check_doorbell(u32 __iomem *doorbell)
+{
+	u32 tmp;
+
+	return readl_poll_timeout(doorbell, tmp, tmp != 0, 0, PSP_CMD_TIMEOUT_US);
+}
+
 /* Recovery field should be equal 0 to start sending commands */
 static int check_recovery(u32 __iomem *cmd)
 {
@@ -132,6 +140,62 @@ unlock:
 }
 EXPORT_SYMBOL_GPL(psp_send_platform_access_msg);
 
+int psp_ring_platform_doorbell(int msg)
+{
+	struct psp_device *psp = psp_get_master_device();
+	struct psp_platform_access_device *pa_dev;
+	u32 __iomem *button, *cmd;
+	int ret, val;
+
+	if (!psp || !psp->platform_access_data)
+		return -ENODEV;
+
+	pa_dev = psp->platform_access_data;
+	button = psp->io_regs + pa_dev->vdata->doorbell_button_reg;
+	cmd = psp->io_regs + pa_dev->vdata->doorbell_cmd_reg;
+
+	mutex_lock(&pa_dev->doorbell_mutex);
+
+	if (check_doorbell(button)) {
+		dev_dbg(psp->dev, "doorbell is not ready\n");
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	if (check_recovery(cmd)) {
+		dev_dbg(psp->dev, "doorbell command in recovery\n");
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	if (wait_cmd(cmd)) {
+		dev_dbg(psp->dev, "doorbell command not done processing\n");
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	iowrite32(FIELD_PREP(PSP_DRBL_MSG, msg), cmd);
+	iowrite32(PSP_DRBL_RING, button);
+
+	if (wait_cmd(cmd)) {
+		ret = -ETIMEDOUT;
+		goto unlock;
+	}
+
+	val = FIELD_GET(PSP_CMDRESP_STS, ioread32(cmd));
+	if (val) {
+		ret = -EIO;
+		goto unlock;
+	}
+
+	ret = 0;
+unlock:
+	mutex_unlock(&pa_dev->doorbell_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;
@@ -140,6 +204,7 @@ void platform_access_dev_destroy(struct psp_device *psp)
 		return;
 
 	mutex_destroy(&pa_dev->mailbox_mutex);
+	mutex_destroy(&pa_dev->doorbell_mutex);
 	psp->platform_access_data = NULL;
 }
 
@@ -159,6 +224,7 @@ int platform_access_dev_init(struct psp_device *psp)
 	pa_dev->vdata = (struct platform_access_vdata *)psp->vdata->platform_access;
 
 	mutex_init(&pa_dev->mailbox_mutex);
+	mutex_init(&pa_dev->doorbell_mutex);
 
 	dev_dbg(dev, "platform access enabled\n");
 

drivers/crypto/ccp/platform-access.h

@@ -24,6 +24,7 @@ struct psp_platform_access_device {
 	struct platform_access_vdata *vdata;
 
 	struct mutex mailbox_mutex;
+	struct mutex doorbell_mutex;
 
 	void *platform_access_data;
 };

drivers/crypto/ccp/sp-dev.h

@@ -57,6 +57,9 @@ struct platform_access_vdata {
 	const unsigned int cmdresp_reg;
 	const unsigned int cmdbuff_addr_lo_reg;
 	const unsigned int cmdbuff_addr_hi_reg;
+	const unsigned int doorbell_button_reg;
+	const unsigned int doorbell_cmd_reg;
+
 };
 
 struct psp_vdata {

drivers/crypto/ccp/sp-pci.c

@@ -365,6 +365,8 @@ static const struct platform_access_vdata pa_v1 = {
 	.cmdresp_reg		= 0x10570,	/* C2PMSG_28 */
 	.cmdbuff_addr_lo_reg	= 0x10574,	/* C2PMSG_29 */
 	.cmdbuff_addr_hi_reg	= 0x10578,	/* C2PMSG_30 */
+	.doorbell_button_reg	= 0x10a24,	/* C2PMSG_73 */
+	.doorbell_cmd_reg	= 0x10a40,	/* C2PMSG_80 */
 };
 
 static const struct psp_vdata pspv1 = {

include/linux/psp-platform-access.h

@@ -34,6 +34,21 @@ 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(int msg);
+
 /**
  * psp_check_platform_access_status() - Checks whether platform features is ready
  *

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 */