2013/11/28 Alexey Brodkin Alexey.Brodkin@synopsys.com:
On Thu, 2013-11-28 at 10:47 +0800, Kuo-Jung Su wrote:
From: Kuo-Jung Su dantesu@faraday-tech.com
The local pointer of address (i.e., addr) only gets referenced in SPI mode, and it won't be appropriate to pass only 1 bytes addr[1] to i2c_read/i2c_write while CONFIG_SYS_I2C_EEPROM_ADDR_LEN > 1.
To avoid ambiguity, this patch would drop the use of address pointer in I2C mode, and directly pass (dev_addr, offset) to i2c_read/i2c_write.
Unfortunately this patch breaks cases with "CONFIG_SYS_I2C_EEPROM_ADDR_LEN = 1" where address is limited to 1 byte
- thus a need to pass "addr[0]" which is combined from real I2C device
address and 256-byte word offset (i.e. MSB part of offset). And "addr[1]" only carries lower 8 bit of offset.
So I would recommend to separate 2 invocations of "i2c_{read|write}":
- for "CONFIG_SYS_I2C_EEPROM_ADDR_LEN = 1"
- for "CONFIG_SYS_I2C_EEPROM_ADDR_LEN > 1"
-Alexey
Hi Alexey:
No it's a common misunderstanding, I also made the same mistake before. Please check my bug fix for Faraday FTI2C010 I2C driver:
http://patchwork.ozlabs.org/patch/294732/
The address should be rebuild inside the i2c driver in u-boot's I2C model.
Another example could be found at drivers/i2c/soft_i2c.c, line 382 - 389
static int soft_i2c_read (...) { ...... shift = (alen-1) * 8; while(alen-- > 0) { if(write_byte(addr >> shift)) { PRINTD("i2c_read, address not <ACK>ed\n"); return(1); } shift -= 8; } ...... }
However the root cause is the u-boot i2c driver model, the address should never be passed to i2c_read/i2c_write in uint format.
Please take a peak at how ecos defineds the relative i2c routines:
externC cyg_uint32 cyg_i2c_transaction_tx(const cyg_i2c_device*, cyg_bool, const cyg_uint8*, cyg_uint32, cyg_bool); externC cyg_uint32 cyg_i2c_transaction_rx(const cyg_i2c_device*, cyg_bool, cyg_uint8*, cyg_uint32, cyg_bool, cyg_bool);
In this way, the eeprom address would be forced to rebuild in address pointer (i.e., addr[]) as what we did in SPI mode.
Best Wishes Kuo-Jung Su