linux-kernel - [PATCH v9 1/2] i2c: riic: Implement bus recovery

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Message-ID: <20250430194647.332553-2-prabhakar.mahadev-lad.rj@bp.renesas.com>
Date: Wed, 30 Apr 2025 20:46:46 +0100
From: Prabhakar <prabhakar.csengg@...il.com>
To: Chris Brandt <chris.brandt@...esas.com>,
	Andi Shyti <andi.shyti@...nel.org>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Andy Shevchenko <andy@...nel.org>
Cc: linux-renesas-soc@...r.kernel.org,
	linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Prabhakar <prabhakar.csengg@...il.com>,
	Biju Das <biju.das.jz@...renesas.com>,
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: [PATCH v9 1/2] i2c: riic: Implement bus recovery

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Implement I2C bus recovery support for the RIIC controller by making use
of software-controlled SCL and SDA line manipulation. The controller allows
forcing SCL and SDA levels through control bits, which enables generation
of manual clock pulses and a stop condition to free a stuck bus.

This implementation wires up the bus recovery mechanism using
i2c_generic_scl_recovery and provides get/set operations for SCL and SDA.

This allows the RIIC driver to recover from bus hang scenarios where SDA
is held low by a slave.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
---
 drivers/i2c/busses/i2c-riic.c | 53 +++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-riic.c b/drivers/i2c/busses/i2c-riic.c
index d7dddd6c296a..740e53bdb2a9 100644
--- a/drivers/i2c/busses/i2c-riic.c
+++ b/drivers/i2c/busses/i2c-riic.c
@@ -53,6 +53,8 @@
 #define ICCR1_IICRST	BIT(6)
 #define ICCR1_SOWP	BIT(4)
 #define ICCR1_SCLI	BIT(1)
+#define ICCR1_SCLO     BIT(3)
+#define ICCR1_SDAO     BIT(2)
 #define ICCR1_SDAI	BIT(0)
 
 #define ICCR2_BBSY	BIT(7)
@@ -151,11 +153,11 @@ static int riic_bus_barrier(struct riic_dev *riic)
 	ret = readb_poll_timeout(riic->base + riic->info->regs[RIIC_ICCR2], val,
 				 !(val & ICCR2_BBSY), 10, riic->adapter.timeout);
 	if (ret)
-		return ret;
+		return i2c_recover_bus(&riic->adapter);
 
 	if ((riic_readb(riic, RIIC_ICCR1) & (ICCR1_SDAI | ICCR1_SCLI)) !=
 	     (ICCR1_SDAI | ICCR1_SCLI))
-		return -EBUSY;
+		return i2c_recover_bus(&riic->adapter);
 
 	return 0;
 }
@@ -439,6 +441,52 @@ static int riic_init_hw(struct riic_dev *riic)
 	return 0;
 }
 
+static int riic_get_scl(struct i2c_adapter *adap)
+{
+	struct riic_dev *riic = i2c_get_adapdata(adap);
+
+	return !!(riic_readb(riic, RIIC_ICCR1) & ICCR1_SCLI);
+}
+
+static int riic_get_sda(struct i2c_adapter *adap)
+{
+	struct riic_dev *riic = i2c_get_adapdata(adap);
+
+	return !!(riic_readb(riic, RIIC_ICCR1) & ICCR1_SDAI);
+}
+
+static void riic_set_scl(struct i2c_adapter *adap, int val)
+{
+	struct riic_dev *riic = i2c_get_adapdata(adap);
+
+	if (val)
+		riic_clear_set_bit(riic, ICCR1_SOWP, ICCR1_SCLO, RIIC_ICCR1);
+	else
+		riic_clear_set_bit(riic, ICCR1_SOWP | ICCR1_SCLO, 0, RIIC_ICCR1);
+
+	riic_clear_set_bit(riic, 0, ICCR1_SOWP, RIIC_ICCR1);
+}
+
+static void riic_set_sda(struct i2c_adapter *adap, int val)
+{
+	struct riic_dev *riic = i2c_get_adapdata(adap);
+
+	if (val)
+		riic_clear_set_bit(riic, ICCR1_SOWP, ICCR1_SDAO, RIIC_ICCR1);
+	else
+		riic_clear_set_bit(riic, ICCR1_SOWP | ICCR1_SDAO, 0, RIIC_ICCR1);
+
+	riic_clear_set_bit(riic, 0, ICCR1_SOWP, RIIC_ICCR1);
+}
+
+static struct i2c_bus_recovery_info riic_bri = {
+	.recover_bus = i2c_generic_scl_recovery,
+	.get_scl = riic_get_scl,
+	.set_scl = riic_set_scl,
+	.get_sda = riic_get_sda,
+	.set_sda = riic_set_sda,
+};
+
 static const struct riic_irq_desc riic_irqs[] = {
 	{ .res_num = 0, .isr = riic_tend_isr, .name = "riic-tend" },
 	{ .res_num = 1, .isr = riic_rdrf_isr, .name = "riic-rdrf" },
@@ -495,6 +543,7 @@ static int riic_i2c_probe(struct platform_device *pdev)
 	adap->algo = &riic_algo;
 	adap->dev.parent = dev;
 	adap->dev.of_node = dev->of_node;
+	adap->bus_recovery_info = &riic_bri;
 
 	init_completion(&riic->msg_done);
 
-- 
2.49.0