All, > -----Original Message----- > From: linux-i2c-owner@xxxxxxxxxxxxxxx [mailto:linux-i2c- > owner@xxxxxxxxxxxxxxx] On Behalf Of Bryan Evenson > Sent: Wednesday, May 24, 2017 2:18 PM > To: linux-i2c@xxxxxxxxxxxxxxx > Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx>; Ludovic Desroches > <ludovic.desroches@xxxxxxxxx> > Subject: Error using at91-i2c driver in kernel 4.4.x > > > I have been using kernel version 3.10.x for a couple years and I am in the > process of upgrading to kernel version 4.4. I am using an Atmel > AT91SAM9G25 and I am using Atmel's stable fork of the kernel at > github.com/linux4sam/linux-at91. I last pulled the linux-4.4-at91 branch > about two weeks ago. Today I noticed that I can no longer talk to an I2C > EEPROM that I could with kernel version 3.10. I verified the EEPROM still > worked with kernel version 3.10 on my hardware, updated my kernel, and > now I can't talk to the EEPROM. > > First, for the ARM device tree the i2c section looks like this for my build: > > i2c0: i2c@f8010000 { > status = "okay"; > > wm8731: wm8731@1a { > compatible = "wm8731"; > reg = <0x1a>; > }; > > ov2640: camera@0x30 { > compatible = "ovti,ov2640"; > reg = <0x30>; > pinctrl-names = "default"; > pinctrl-0 = <&pinctrl_pck0_as_isi_mck > &pinctrl_sensor_power &pinctrl_sensor_reset>; > resetb-gpios = <&pioA 7 GPIO_ACTIVE_LOW>; > pwdn-gpios = <&pioA 13 GPIO_ACTIVE_HIGH>; > clocks = <&pck0>; > clock-names = "xvclk"; > assigned-clocks = <&pck0>; > assigned-clock-rates = <25000000>; > status = "disabled"; > > port { > ov2640_0: endpoint { > remote-endpoint = <&isi_0>; > bus-width = <8>; > }; > }; > }; > 24c02@50 { > compatible = "atmel,24c02"; > reg = <0x50>; > pagesize = <0x08>; > status = "okay"; > }; > }; > > I see the following messages in dmesg: > > [ 0.234375] at91_i2c f8010000.i2c: using dma0chan0 (tx) and dma0chan1 (rx) > for DMA transfers > [ 0.234375] at91_i2c f8010000.i2c: AT91 i2c bus driver (hw version: 0x402). > [ 0.742187] at24 0-0050: 256 byte 24c02 EEPROM, writable, 8 bytes/write > [ 1.343750] i2c /dev entries driver > > To me it appears the i2c driver and the EEPROM driver have been loaded and > populated. I see that /dev/i2c-0 and /sys/class/i2c-dev/i2c-0 are populated > on my system. I then try to read all 256 bytes from the EEPROM as follows > from my C program: > > int file; > char filename[] = "/dev/i2c-0"; > int addr = 0x50; > char buf[256]; > ssize_t readBytes; > > /* Open the I2C dev interface file */ > file = open(filename, O_RDWR); > if (file < 0) > { > printf("Can't open device\n"); > exit(EXIT_FAILURE); > } > > /* Set the I2C slave address */ > if (ioctl(file, I2C_SLAVE, addr) < 0) > { > printf("Can't set slave address - %m\n"); > } > > /* Attempt to read out the entire EEPROM */ > readBytes = read(file, buf, sizeof(buf)); > if(readBytes != (ssize_t)sizeof(buf)) > { > printf("Only read %d bytes\n - %m", readBytes); > } > else > { > /* Do something with the data... */ > } > > When I run the above code with the 4.4 kernel running, I get the following > output: > > Can't set slave address - Device or resource busy > Only read -1 bytes - Remote I/O error > > Any thoughts as to what I should be checking to figure out why i2c isn't > working for me anymore? As usual, five minutes after I ask a question I get further. I tried changing the ioctl to I2C_SLAVE_FORCE, and now I can talk to my EEPROM. I'm happy it's now working, but I'm concerned about why I now need to force the slave address. Is this because I now need to set things up differently, or is it a problem with the driver? Thanks, Bryan > > Thanks, > Bryan > > -- > 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 -- 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
