From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heiko Schocher Date: Mon, 09 Dec 2013 07:57:14 +0100 Subject: [U-Boot] [U-Boot, V2] arm: omap: i2c: don't zero cnt in i2c_write In-Reply-To: <1385654682-2775-1-git-send-email-nikita@compulab.co.il> References: <1385654682-2775-1-git-send-email-nikita@compulab.co.il> Message-ID: <52A569CA.3050608@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hello Nikita, Am 28.11.2013 17:04, schrieb Nikita Kiryanov: > Writing zero into I2Ci.I2C_CNT register causes random I2C failures in OMAP3 > based devices. This seems to be related to the following advisory which > apears in multiple erratas for OMAP3 SoCs (OMAP35xx, DM37xx), as well as > OMAP4430 TRM: > > Advisory: > I2C Module Does Not Allow 0-Byte Data Requests > Details: > When configured as the master, the I2C module does not allow 0-byte data > transfers. Note: Programming I2Ci.I2C_CNT[15:0]: DCOUNT = 0 will cause > undefined behavior. > Workaround(s): > No workaround. Do not use 0-byte data requests. > > The writes in question are unnecessary from a functional point of view. > Most of them are done after I/O has finished, and the only one that preceds > I/O (in i2c_probe()) is also unnecessary because a stop bit is sent before > actual data transmission takes place. > > Therefore, remove all writes that zero the cnt register. > > Cc: Heiko Schocher > Cc: Thomas Petazzoni > Cc: Tom Rini > Cc: Lubomir Popov > Cc: Enric Balletbo Serra > Signed-off-by: Nikita Kiryanov > Tested-by: Thomas Petazzoni > Tested-by: Lubomir Popov > > --- > Changes in V2: > Removed all instances of writew(0,&i2c_base->cnt) instead of just the > one in i2c_write (following a test of V1 by Thomas Petazzoni). > > drivers/i2c/omap24xx_i2c.c | 6 ------ > 1 file changed, 6 deletions(-) Thanks! Applied to u-boot-i2c.git. bye, Heiko -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany