AW: [PATCH v5 3/4] drivers/i2c/busses/i2c-at91.c: add new driver
Hi, I try to use the at24 eeprom driver on top of this driver. This EEPROM (24c32) works with two address bytes. Writing results in a call to at91_twi_xfer() with num=1. In this case the internal address register is not used and the address is sent out within the buffer. Reading results in a call to at91_twi_xfer() with num=2. In this case the internal address register is used. However the MSB of the internal address resides in msg->buf[0] and the LSB resides in msg->buf[1] of the first message. As a result the code: + for (i = 0; i < msg->len; ++i) { + internal_address |= ((unsigned)msg->buf[i]) << (8 * i); + int_addr_flag += AT91_TWI_IADRSZ_1; + } + at91_twi_write(dev, AT91_TWI_IADR, internal_address); constructs an internal address in a wrong byte order. Example: Try to read from address 0x100: msg[0]->buf[0] = 0x1; msg[0]->buf[1] = 0x0; results in internal_address = 0x1; I think it must be: + for (i = 0; i < msg->len; ++i) { + internal_address |= ((unsigned)msg->buf[msg->len-1-i]) << (8 * i); + int_addr_flag += AT91_TWI_IADRSZ_1; + } + at91_twi_write(dev, AT91_TWI_IADR, internal_address); ... or the at24 eeprom driver constructs the wrong internal address ... Mit freundlichen Grüßen / Best regards Carsten Behling Development Engineer Garz & Fricke GmbH Tempowerkring 2, 21079 Hamburg - Germany Amtsgericht Hamburg HRB 60514 Geschäftsführer: Manfred Garz, Matthias Fricke Phone: +49 (0) 40 791 899 - 56 Fax:+49 40 / 791 899 - 39 www.garz-fricke.com -Ursprüngliche Nachricht- Von: Voss, Nikolaus [mailto:n.v...@weinmann.de] Gesendet: Mittwoch, 23. November 2011 11:29 An: Carsten Behling Cc: 'linux-i2c@vger.kernel.org'; 'linux-arm-ker...@lists.infradead.org'; 'linux-ker...@vger.kernel.org' Betreff: RE: [PATCH v5 3/4] drivers/i2c/busses/i2c-at91.c: add new driver Hi, Carsten Behling wrote on 2011-11-23: >> this case is already catched in at91_do_twi_transfer(): > > Sorry, I did not found this code in your patch. > (http://www.mail-archive.com/linux-i2c@vger.kernel.org/msg06556.html): > >> + if (is_read) { >> + if (!dev->buf_len) yes, this won't work for buf_len == 1. It is corrected in https://lkml.org/lkml/2011/11/18/223 which I held back for some time as it should have been just a feature extension. I was not aware it also fixed the buf_len = 1 bug. Sorry for that... (Explanation: in the first implementation I immediately decremented buf_len, so buf_len == 1 could not occur. Later I removed that but did not fully fold it into the base patch.) Thanks, Niko -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
AW: [PATCH v5 3/4] drivers/i2c/busses/i2c-at91.c: add new driver
> this case is already catched in at91_do_twi_transfer(): Sorry, I did not found this code in your patch. (http://www.mail-archive.com/linux-i2c@vger.kernel.org/msg06556.html): > + if (is_read) { > + if (!dev->buf_len) > + at91_twi_write(dev, AT91_TWI_CR, > + AT91_TWI_START | AT91_TWI_STOP); > + else > + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_START); > + at91_twi_write(dev, AT91_TWI_IER, > + AT91_TWI_TXCOMP | AT91_TWI_RXRDY); > + } else { > + at91_twi_write_next_byte(dev); > + at91_twi_write(dev, AT91_TWI_IER, > + AT91_TWI_TXCOMP | AT91_TWI_TXRDY); > + } Is there a more recent version ? Mit freundlichen Grüßen / Best regards Carsten Behling Development Engineer Garz & Fricke GmbH Tempowerkring 2, 21079 Hamburg - Germany Amtsgericht Hamburg HRB 60514 Geschäftsführer: Manfred Garz, Matthias Fricke Phone: +49 (0) 40 791 899 - 56 Fax:+49 40 / 791 899 - 39 www.garz-fricke.com -Ursprüngliche Nachricht- Von: Voss, Nikolaus [mailto:n.v...@weinmann.de] Gesendet: Dienstag, 22. November 2011 17:26 An: Carsten Behling Cc: 'linux-i2c@vger.kernel.org'; 'linux-arm-ker...@lists.infradead.org'; 'linux-ker...@vger.kernel.org' Betreff: RE: [PATCH v5 3/4] drivers/i2c/busses/i2c-at91.c: add new driver Hi, Carsten Behling wrote on 2011-11-22: > +static void at91_twi_read_next_byte(struct at91_twi_dev *dev) > +{ > + *dev->buf = at91_twi_read(dev, AT91_TWI_RHR) & 0xff; > + > + /* send stop if second but last byte has been read */ > + if (--dev->buf_len == 1) > + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP); > > > > If dev->buf_len =1 at the beginning of a read transfer, a stop condition will > never be send. this case is already catched in at91_do_twi_transfer(): + if (dev->msg->flags & I2C_M_RD) { + unsigned start_flags = AT91_TWI_START; + + /* if only one byte is to be read, immediately stop transfer */ + if (dev->buf_len <= 1 && !(dev->msg->flags & I2C_M_RECV_LEN)) + start_flags |= AT91_TWI_STOP; + at91_twi_write(dev, AT91_TWI_CR, start_flags); Thanks for reviewing, Niko -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html