From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Eric Anholt <eric@anholt.net>,
Stefan Wahren <stefan.wahren@i2se.com>,
Wolfram Sang <wsa@kernel.org>, Sasha Levin <sashal@kernel.org>,
nsaenz@kernel.org, f.fainelli@gmail.com, rjui@broadcom.com,
sbranden@broadcom.com, bcm-kernel-feedback-list@broadcom.com,
prabhakar.mahadev-lad.rj@bp.renesas.com,
linux-i2c@vger.kernel.org, linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH AUTOSEL 4.19 03/13] i2c: bcm2835: Avoid clock stretching timeouts
Date: Tue, 22 Feb 2022 21:31:42 -0500 [thread overview]
Message-ID: <20220223023152.242065-3-sashal@kernel.org> (raw)
In-Reply-To: <20220223023152.242065-1-sashal@kernel.org>
From: Eric Anholt <eric@anholt.net>
[ Upstream commit 9495b9b31abe525ebd93da58de2c88b9f66d3a0e ]
The CLKT register contains at poweron 0x40, which at our typical 100kHz
bus rate means .64ms. But there is no specified limit to how long devices
should be able to stretch the clocks, so just disable the timeout. We
still have a timeout wrapping the entire transfer.
Signed-off-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
BugLink: https://github.com/raspberrypi/linux/issues/3064
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/i2c/busses/i2c-bcm2835.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index 4d19254f78c8a..db1ab9ccc30e7 100644
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -28,6 +28,11 @@
#define BCM2835_I2C_FIFO 0x10
#define BCM2835_I2C_DIV 0x14
#define BCM2835_I2C_DEL 0x18
+/*
+ * 16-bit field for the number of SCL cycles to wait after rising SCL
+ * before deciding the slave is not responding. 0 disables the
+ * timeout detection.
+ */
#define BCM2835_I2C_CLKT 0x1c
#define BCM2835_I2C_C_READ BIT(0)
@@ -398,6 +403,12 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
adap->dev.of_node = pdev->dev.of_node;
adap->quirks = &bcm2835_i2c_quirks;
+ /*
+ * Disable the hardware clock stretching timeout. SMBUS
+ * specifies a limit for how long the device can stretch the
+ * clock, but core I2C doesn't.
+ */
+ bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_CLKT, 0);
bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
ret = i2c_add_adapter(adap);
--
2.34.1
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parent reply other threads:[~2022-02-23 2:34 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20220223023152.242065-1-sashal@kernel.org>]
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