linux-kernel - [PATCH 1/3] i2c: meson: fix clock setting overwrite

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Date:   Wed,  7 Oct 2020 10:07:49 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Wolfram Sang <wsa@...nel.org>, Kevin Hilman <khilman@...libre.com>
Cc:     Jerome Brunet <jbrunet@...libre.com>,
        Nicolas Belin <nbelin@...libre.com>, linux-i2c@...r.kernel.org,
        linux-amlogic@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] i2c: meson: fix clock setting overwrite

When the slave address is written in do_start(), SLAVE_ADDR is written
completely. This may overwrite some setting related to the clock rate
or signal filtering.

Fix this by writing only the bits related to slave address. To avoid
causing unexpected changed, explicitly disable filtering or high/low
clock mode which may have been left over by the bootloader.

Fixes: 30021e3707a7 ("i2c: add support for Amlogic Meson I2C controller")
Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
---
 drivers/i2c/busses/i2c-meson.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-meson.c b/drivers/i2c/busses/i2c-meson.c
index c5dec572fc48..dac0d2a00cec 100644
--- a/drivers/i2c/busses/i2c-meson.c
+++ b/drivers/i2c/busses/i2c-meson.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2014 Beniamino Galvani <b.galvani@...il.com>
  */
 
+#include <linux/bitfield.h>
 #include <linux/clk.h>
 #include <linux/completion.h>
 #include <linux/i2c.h>
@@ -38,6 +39,12 @@
 #define REG_CTRL_CLKDIVEXT_SHIFT 28
 #define REG_CTRL_CLKDIVEXT_MASK	GENMASK(29, 28)
 
+#define REG_SLV_ADDR		GENMASK(7, 0)
+#define REG_SLV_SDA_FILTER	GENMASK(10, 8)
+#define REG_SLV_SCL_FILTER	GENMASK(13, 11)
+#define REG_SLV_SCL_LOW		GENMASK(27, 16)
+#define REG_SLV_SCL_LOW_EN	BIT(28)
+
 #define I2C_TIMEOUT_MS		500
 
 enum {
@@ -147,6 +154,9 @@ static void meson_i2c_set_clk_div(struct meson_i2c *i2c, unsigned int freq)
 	meson_i2c_set_mask(i2c, REG_CTRL, REG_CTRL_CLKDIVEXT_MASK,
 			   (div >> 10) << REG_CTRL_CLKDIVEXT_SHIFT);
 
+	/* Disable HIGH/LOW mode */
+	meson_i2c_set_mask(i2c, REG_SLAVE_ADDR, REG_SLV_SCL_LOW_EN, 0);
+
 	dev_dbg(i2c->dev, "%s: clk %lu, freq %u, div %u\n", __func__,
 		clk_rate, freq, div);
 }
@@ -280,7 +290,10 @@ static void meson_i2c_do_start(struct meson_i2c *i2c, struct i2c_msg *msg)
 	token = (msg->flags & I2C_M_RD) ? TOKEN_SLAVE_ADDR_READ :
 		TOKEN_SLAVE_ADDR_WRITE;
 
-	writel(msg->addr << 1, i2c->regs + REG_SLAVE_ADDR);
+
+	meson_i2c_set_mask(i2c, REG_SLAVE_ADDR, REG_SLV_ADDR,
+			   FIELD_PREP(REG_SLV_ADDR, msg->addr << 1));
+
 	meson_i2c_add_token(i2c, TOKEN_START);
 	meson_i2c_add_token(i2c, token);
 }
@@ -461,6 +474,10 @@ static int meson_i2c_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/* Disable filtering */
+	meson_i2c_set_mask(i2c, REG_SLAVE_ADDR,
+			   REG_SLV_SDA_FILTER | REG_SLV_SCL_FILTER, 0);
+
 	meson_i2c_set_clk_div(i2c, timings.bus_freq_hz);
 
 	return 0;
-- 
2.25.4