-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi, It really seems like what I observed in http://www.spinics.net/lists/linux-i2c/msg11985.html I still didn't have a deeper look at it. Also, ccing Fabio that seemed interested in the resoultion of that issue On 28/06/2013 11:13, Wolfram Sang wrote: > > CCing Marek Vasut and Pengutronix... > > On Thu, Jun 27, 2013 at 07:39:45PM +0200, Torsten Fleischer wrote: >> Hi, >> >> on my board there is a temperature sensor TCN75A (compatible to LM75) >> connected to the iMX283. >> In the user space the temperature is periodically polled by reading the file >> /sys/bus/i2c/devices/0-0048/temp1_input. >> When triggering this file the LM75 driver consecutively reads 3 registers from >> the sensor and outputs the current temperature read from register 0. >> >> With linux 3.9.7 I sometimes get a communication timeout when reading the >> sensor. >> >> Since several patches have been added to the driver, I tried linux 3.10-rc7. >> With this version no timeout will be reported, but sometimes the value >> returned seems to be wrong. Normally I get a value of round about 30000. But >> sometimes it takes some seconds to read the temperature and the returned value >> is 75000. This value is not the current temperature but the temperature >> hysteresis that is the content of register 2 of the sensor. >> >> After some investigation I found that the i2c-mxs driver sometimes times out >> while waiting for the MXS_I2C_DEBUG0_DMAREQ bit when writing data (the >> I2C_M_RD flag is not set). >> Unfortunately this error is never reported to the I2C core and thus to the >> LM75 driver. So the LM75 driver assumes that it has received the correct >> values. >> >> This problem seems to be only in the PIO mode. After changing the driver so >> that the DMA is always used it works as expected. >> >> Best regards, >> Torsten Fleischer >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-i2c" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html - -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with undefined - http://www.enigmail.net/ iQIcBAEBCAAGBQJRzV26AAoJEKbNnwlvZCyzkQAP/RjzuLb3rq7GR4IFizpFJ/u7 VbPQuNO6xgFRU5kqB4tmrljxdXDt84Xecgh+dFpOF5CcIDb8ap8x3JN6RTVNFu5a XGKY2INImW7ShAiw8ZrB/lylRcD/5rwfEnIwpkcx9v2CaNlFbDjAxOmprrkwrI0t uuCzbhk0l8FHG1RaAzvvPaD8Aai05qwuIvkwwtoT539zVVGx+xb2f0I7i5/3NhML 5N35EPnTwG1k1yi8IemUauf9uPCjKR02vYiTJa+rURVjxa+7RjLP+wHd49JMvbln CzXNbbnUtKFfIOARFclCzCoMOIp9J9VtbpWy4vvBeHBrj8I8hKqyL0tMmwu3ReKl FATYCbJVTD9ipjesB2KIUf8vUgVJJZWzOAZWWEeC2x0E2EGj0LdNY7Emmu6u3kWp 5PL6ra6iU1DxPwuFVN1hr3kLvvoI/8d1m4+aMg13VnA+C+h/EeWalZF9ULt4QK99 cPGRwxMRUfZsQFv515XVUeaeiYnd4vAMPZfmMl5WL7LDN6jqkeeM0nJm4jgfGmIv 2PzLhcOyOpSnkONVzn2A/G+948LI3odv6plWjnDqPWcl83zAIFyYmA2NmDirYX1W JU0DSU26un90IZw0AjwlTeOOxEtE8+KheKFHR7YBj91m36DPvlxZL0kQOL67ibBi VHt7PanQ3OvbKC70AqCA =aY1b -----END PGP SIGNATURE----- -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
