linux-kernel - [PATCH v6 3/5] i3c: dw: Add support for Device NACK Retry configuration

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Message-ID: <c66b447dbf6cfbc0f306ae78f0d886c3ad65a3e7.1764746266.git.adrianhoyin.ng@altera.com>
Date: Wed,  3 Dec 2025 15:21:04 +0800
From: adrianhoyin.ng@...era.com
To: alexandre.belloni@...tlin.com,
	Frank.Li@....com,
	linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: adrianhoyin.ng@...era.com
Subject: [PATCH v6 3/5] i3c: dw: Add support for Device NACK Retry configuration

From: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>

The DesignWare I3C controller supports automatically retrying transactions
when a device NACKs. This is useful for slave devices that may be
temporarily busy and not ready to respond immediately.

Add new ops to configure all active DAT entry with dev_nack_retry during
runtime. Returns error when value exceeds hw specified limit.

Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
---
 drivers/i3c/master/dw-i3c-master.c | 39 ++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index 9ceedf09c3b6..252559ee2afa 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -5,6 +5,7 @@
  * Author: Vitor Soares <vitor.soares@...opsys.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/clk.h>
 #include <linux/completion.h>
@@ -204,8 +205,12 @@
 #define EXTENDED_CAPABILITY		0xe8
 #define SLAVE_CONFIG			0xec
 
+#define DW_I3C_DEV_NACK_RETRY_CNT_MAX	0x3
+#define DEV_ADDR_TABLE_DEV_NACK_RETRY_MASK   GENMASK(30, 29)
 #define DEV_ADDR_TABLE_IBI_MDB		BIT(12)
 #define DEV_ADDR_TABLE_SIR_REJECT	BIT(13)
+#define DEV_ADDR_TABLE_DEV_NACK_RETRY_CNT(x) \
+	FIELD_PREP(DEV_ADDR_TABLE_DEV_NACK_RETRY_MASK, (x))
 #define DEV_ADDR_TABLE_LEGACY_I2C_DEV	BIT(31)
 #define DEV_ADDR_TABLE_DYNAMIC_ADDR(x)	(((x) << 16) & GENMASK(23, 16))
 #define DEV_ADDR_TABLE_STATIC_ADDR(x)	((x) & GENMASK(6, 0))
@@ -1484,6 +1489,39 @@ static irqreturn_t dw_i3c_master_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+static int dw_i3c_master_set_dev_nack_retry(struct i3c_master_controller *m)
+{
+	struct dw_i3c_master *master = to_dw_i3c_master(m);
+	u32 reg;
+	int i;
+
+	if (m->dev_nack_retry > DW_I3C_DEV_NACK_RETRY_CNT_MAX) {
+		dev_err(&master->base.dev,
+			"Value %x exceeds maximum %d\n",
+			m->dev_nack_retry, DW_I3C_DEV_NACK_RETRY_CNT_MAX);
+		return -ERANGE;
+	}
+
+	/*
+	 * Update DAT entries for all currently attached devices.
+	 * We directly iterate through the master's device array.
+	 */
+	for (i = 0; i < master->maxdevs; i++) {
+		/* Skip free/empty slots */
+		if (master->free_pos & BIT(i))
+			continue;
+
+		reg = readl(master->regs +
+				DEV_ADDR_TABLE_LOC(master->datstartaddr, i));
+		reg &= ~DEV_ADDR_TABLE_DEV_NACK_RETRY_MASK;
+		reg |= DEV_ADDR_TABLE_DEV_NACK_RETRY_CNT(m->dev_nack_retry);
+		writel(reg, master->regs +
+			DEV_ADDR_TABLE_LOC(master->datstartaddr, i));
+	}
+
+	return 0;
+}
+
 static const struct i3c_master_controller_ops dw_mipi_i3c_ops = {
 	.bus_init = dw_i3c_master_bus_init,
 	.bus_cleanup = dw_i3c_master_bus_cleanup,
@@ -1504,6 +1542,7 @@ static const struct i3c_master_controller_ops dw_mipi_i3c_ops = {
 	.recycle_ibi_slot = dw_i3c_master_recycle_ibi_slot,
 	.enable_hotjoin = dw_i3c_master_enable_hotjoin,
 	.disable_hotjoin = dw_i3c_master_disable_hotjoin,
+	.set_dev_nack_retry = dw_i3c_master_set_dev_nack_retry,
 };
 
 /* default platform ops implementations */
-- 
2.49.GIT