[PATCH 8/8] i3c: mipi-i3c-hci: Add Hot-Join support

[Adrian Hunter]

Wire the MIPI I3C HCI driver into the I3C core Hot-Join framework to
allow targets to dynamically join the bus after initial DAA.

HCI hardware ACKs or NACKs Hot-Join requests based on
HC_CONTROL.HOT_JOIN_CTRL.  This was previously left in the
NACK-and-DISEC state, effectively preventing Hot-Join.  Implement
the ->enable_hotjoin() and ->disable_hotjoin() master operations
so the core and user space can control this policy at runtime.

Also issue broadcast ENEC HJ when enabling Hot-Join.  This is required
because the controller may have previously DISEC'ed the Hot-Join
event, causing targets that were NACKed once to never retry.

Acknowledged Hot-Join requests are delivered as IBIs on the reserved
address 0x02.  Update both the DMA and PIO IBI paths to recognise this
address and forward the event to i3c_master_queue_hotjoin().

To make Hot-Join usable by default, enable it once after the initial
DAA.  This is gated by rpm_ibi_allowed, since otherwise keeping Hot-Join
enabled prevents runtime suspend.  A new hj_init_done flag ensures this
one-time enablement is not repeated on subsequent DAAs.

Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
---
 drivers/i3c/master/mipi-i3c-hci/core.c | 50 ++++++++++++++++++++++++--
 drivers/i3c/master/mipi-i3c-hci/dma.c  |  5 +++
 drivers/i3c/master/mipi-i3c-hci/hci.h  |  1 +
 drivers/i3c/master/mipi-i3c-hci/pio.c  |  5 +++
 4 files changed, 58 insertions(+), 3 deletions(-)

diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
index 2866d599612a..f8b399d16598 100644
--- a/drivers/i3c/master/mipi-i3c-hci/core.c
+++ b/drivers/i3c/master/mipi-i3c-hci/core.c
@@ -392,11 +392,52 @@ static int i3c_hci_send_ccc_cmd(struct i3c_master_controller *m,
 	return ret;
 }
 
+static int i3c_hci_enable_hotjoin(struct i3c_master_controller *m)
+{
+	struct i3c_hci *hci = to_i3c_hci(m);
+	int ret;
+
+	reg_clear(HC_CONTROL, HC_CONTROL_HOT_JOIN_CTRL);
+
+	/*
+	 * Broadcast Hot_join enable, so that an I3C device that has previously
+	 * had its Hot-Join request NACK'ed knows to try again.
+	 */
+	ret = i3c_master_enec_disec_locked(m, I3C_BROADCAST_ADDR, true, I3C_CCC_EVENT_HJ, true);
+	if (ret) {
+		reg_set(HC_CONTROL, HC_CONTROL_HOT_JOIN_CTRL);
+		dev_err(&hci->master.dev, "Hot-Join ENEC CCC failed\n");
+	}
+
+	return ret;
+}
+
+static int i3c_hci_disable_hotjoin(struct i3c_master_controller *m)
+{
+	struct i3c_hci *hci = to_i3c_hci(m);
+
+	reg_set(HC_CONTROL, HC_CONTROL_HOT_JOIN_CTRL);
+	return 0;
+}
+
 static int i3c_hci_daa(struct i3c_master_controller *m)
 {
 	struct i3c_hci *hci = to_i3c_hci(m);
+	int ret;
 
-	return hci->cmd->perform_daa(hci);
+	ret = hci->cmd->perform_daa(hci);
+
+	if (!hci->hj_init_done) {
+		hci->hj_init_done = true;
+		/*
+		 * Enable Hot-Join by default after initial DAA if it does not
+		 * prevent runtime suspend.
+		 */
+		if (m->rpm_ibi_allowed && !ret)
+			m->hotjoin = !i3c_hci_enable_hotjoin(m);
+	}
+
+	return ret;
 }
 
 static int i3c_hci_i3c_xfers(struct i3c_dev_desc *dev,
@@ -652,6 +693,8 @@ static const struct i3c_master_controller_ops i3c_hci_ops = {
 	.enable_ibi		= i3c_hci_enable_ibi,
 	.disable_ibi		= i3c_hci_disable_ibi,
 	.recycle_ibi_slot	= i3c_hci_recycle_ibi_slot,
+	.enable_hotjoin		= i3c_hci_enable_hotjoin,
+	.disable_hotjoin	= i3c_hci_disable_hotjoin,
 };
 
 static irqreturn_t i3c_hci_irq_handler(int irq, void *dev_id)
@@ -833,8 +876,9 @@ static int i3c_hci_do_reset_and_restore(struct i3c_hci *hci)
 	scoped_guard(spinlock_irqsave, &hci->lock)
 		hci->irq_inactive = false;
 
-	/* Enable bus with Hot-Join disabled */
-	reg_set(HC_CONTROL, HC_CONTROL_BUS_ENABLE | HC_CONTROL_HOT_JOIN_CTRL);
+	/* Enable bus, restoring hot-join state */
+	reg_set(HC_CONTROL,
+		HC_CONTROL_BUS_ENABLE | (hci->master.hotjoin ? 0 : HC_CONTROL_HOT_JOIN_CTRL));
 
 	return 0;
 }
diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
index e5deeba0aa4e..34129ac039dc 100644
--- a/drivers/i3c/master/mipi-i3c-hci/dma.c
+++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
@@ -971,6 +971,11 @@ static void hci_dma_process_ibi(struct i3c_hci *hci, struct hci_rh_data *rh)
 	}
 
 	/* determine who this is for */
+	if (ibi_addr == I3C_HOT_JOIN_ADDR) {
+		i3c_master_queue_hotjoin(&hci->master);
+		goto done;
+	}
+
 	dev = i3c_hci_addr_to_dev(hci, ibi_addr);
 	if (!dev) {
 		dev_err(&hci->master.dev,
diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
index 243d7a67f6f6..591eea040b01 100644
--- a/drivers/i3c/master/mipi-i3c-hci/hci.h
+++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
@@ -57,6 +57,7 @@ struct i3c_hci {
 	bool irq_inactive;
 	bool enqueue_blocked;
 	bool recovery_needed;
+	bool hj_init_done;
 	wait_queue_head_t enqueue_wait_queue;
 	u32 caps;
 	unsigned int quirks;
diff --git a/drivers/i3c/master/mipi-i3c-hci/pio.c b/drivers/i3c/master/mipi-i3c-hci/pio.c
index 6b8cc5f2b4d2..b5ae1cfaa9e0 100644
--- a/drivers/i3c/master/mipi-i3c-hci/pio.c
+++ b/drivers/i3c/master/mipi-i3c-hci/pio.c
@@ -862,6 +862,11 @@ static bool hci_pio_prep_new_ibi(struct i3c_hci *hci, struct hci_pio_data *pio)
 	ibi->seg_len = FIELD_GET(IBI_DATA_LENGTH, ibi_status);
 	ibi->seg_cnt = ibi->seg_len;
 
+	if (ibi->addr == I3C_HOT_JOIN_ADDR) {
+		i3c_master_queue_hotjoin(&hci->master);
+		return true;
+	}
+
 	dev = i3c_hci_addr_to_dev(hci, ibi->addr);
 	if (!dev) {
 		dev_err(&hci->master.dev,
-- 
2.51.0