From: Matt Weber <matthew.weber@rockwellcollins.com>
To: linux-i2c@vger.kernel.org
Cc: wsa@the-dreams.de, soren.brinkmann@xilinx.com,
Matt Weber <matthew.weber@rockwellcollins.com>,
John Linn <john.linn@xilinx.com>,
Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>
Subject: [PATCH 1/1] i2c: cadance: (bugfix) ctrl/addr reg write order
Date: Wed, 21 Jun 2017 20:45:26 -0500 [thread overview]
Message-ID: <1498095926-51264-1-git-send-email-matthew.weber@rockwellcollins.com> (raw)
The driver was clearing the hold bit in the control register before
writing to the address register which resulted in a stop condition
being generated rather than a repeated start.
This issue was only observed when a system was running much
slower than a normal processor would execute. The IP data sheet
mentions a ordering of writing to the address register before
clearing the hold.
Signed-off-by: John Linn <john.linn@xilinx.com>
Signed-off-by: Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>
Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
---
drivers/i2c/busses/i2c-cadence.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-cadence.c
index 45d6771..75d8016 100644
--- a/drivers/i2c/busses/i2c-cadence.c
+++ b/drivers/i2c/busses/i2c-cadence.c
@@ -405,14 +405,14 @@ static void cdns_i2c_mrecv(struct cdns_i2c *id)
cdns_i2c_writereg(id->recv_count, CDNS_I2C_XFER_SIZE_OFFSET);
}
+ /* Set the slave address in address register - triggers operation */
+ cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
+ CDNS_I2C_ADDR_OFFSET);
/* Clear the bus hold flag if bytes to receive is less than FIFO size */
if (!id->bus_hold_flag &&
((id->p_msg->flags & I2C_M_RECV_LEN) != I2C_M_RECV_LEN) &&
(id->recv_count <= CDNS_I2C_FIFO_DEPTH))
cdns_i2c_clear_bus_hold(id);
- /* Set the slave address in address register - triggers operation */
- cdns_i2c_writereg(id->p_msg->addr & CDNS_I2C_ADDR_MASK,
- CDNS_I2C_ADDR_OFFSET);
cdns_i2c_writereg(CDNS_I2C_ENABLED_INTR_MASK, CDNS_I2C_IER_OFFSET);
}
--
1.9.1
next reply other threads:[~2017-06-22 1:55 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-22 1:45 Matt Weber [this message]
2017-06-22 8:35 ` [PATCH 1/1] i2c: cadance: (bugfix) ctrl/addr reg write order Wolfram Sang
2017-06-22 11:34 ` Matthew Weber
2017-06-22 13:26 ` Wolfram Sang
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