From: Alok Chauhan <alokc@nvidia.com>
To: khali@linux-fr.org, ben-linux@fluff.org, swarren@nvidia.com,
olof@lixom.net, bones@secretlab.ca, paul.gortmaker@windriver.com,
dgreid@google.com, ldewangan@nvidia.com
Cc: linux-tegra@vger.kernel.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org, Alok Chauhan <alokc@nvidia.com>
Subject: [PATCH v2] i2c: tegra: Add delay before reset the controller
Date: Mon, 26 Dec 2011 16:44:41 +0530 [thread overview]
Message-ID: <1324898081-10308-1-git-send-email-alokc@nvidia.com> (raw)
From: Alok Chauhan <alokc@nvidia.com>
In NACK error condition, I2C controller violates
clock-to-data setup time before stop. In Software,
because of this reset of controller is happening
before I2C controller could complete STOP condition.
Added delay of 2 clock period before reset the
controller in case of NACK error.
Signed-off-by: Alok Chauhan <alokc@nvidia.com>
---
Instead of setting constant value for delay as was in previous patch, now in
the current modification delay will be calculated based on clock frequency of the bus.
drivers/i2c/busses/i2c-tegra.c | 8 ++++++++
1 files changed, 8 insertions(+), 0 deletions(-)
diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 6381604..62e197c 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -517,6 +517,14 @@ static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
if (likely(i2c_dev->msg_err == I2C_ERR_NONE))
return 0;
+ /*
+ * In NACK error condition resetting of I2C controller happens
+ * before STOP condition is properly completed by I2C controller,
+ * so wait for 2 clock cycle to complete STOP condition.
+ */
+ if (i2c_dev->msg_err == I2C_ERR_NO_ACK)
+ udelay(DIV_ROUND_UP(2 * 1000000, i2c_dev->bus_clk_rate));
+
tegra_i2c_init(i2c_dev);
if (i2c_dev->msg_err == I2C_ERR_NO_ACK) {
if (msg->flags & I2C_M_IGNORE_NAK)
--
1.7.4.1
next reply other threads:[~2011-12-26 11:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-26 11:14 Alok Chauhan [this message]
2012-01-06 16:18 ` [PATCH v2] i2c: tegra: Add delay before reset the controller Ben Dooks
2012-01-10 4:12 ` Alok Chauhan
2012-02-10 9:20 ` Alok Chauhan
2012-02-10 9:35 ` Shubhrajyoti Datta
2012-02-14 5:49 ` Alok Chauhan
2012-03-08 6:29 ` Alok Chauhan
2012-04-02 5:53 Alok Chauhan
2012-04-02 5:59 ` Alok Chauhan
2012-04-02 10:19 ` Shubhrajyoti Datta
2012-04-02 12:06 ` Alok Chauhan
2012-04-02 19:58 ` Stephen Warren
2012-04-13 22:51 ` Stephen Warren
2012-04-18 14:27 ` Wolfram Sang
2012-04-18 20:02 ` Stephen Warren
2012-04-18 20:20 ` Wolfram Sang
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