Re: [U-Boot] [PATCH 1/7] powerpc/i2c: introduce CONFIG_I2C_TWR for setting tWR value

Hello York,

York Sun wrote:

From: york yorksun@freescale.com

EEPROM requires tWR for write cycle time. Since there is no other way to poll if the internal programming ends, wait for 5ms which is the max timing for AT24C01/02/04/08/16 by default. It can be overridden by defining CONFIG_I2C_TWR in configuration file if the slowest device has different write cycle time.

Signed-off-by: York Sun yorksun@freescale.com

README | 7 +++++++ drivers/i2c/fsl_i2c.c | 9 +++++++++ 2 files changed, 16 insertions(+), 0 deletions(-)

diff --git a/README b/README index 8bb9c8d..83a316c 100644 --- a/README +++ b/README @@ -1717,6 +1717,13 @@ The following options need to be configured: devices can use either method, but some require one or the other.

• CONFIG_I2C_TWR
  

Maybe CONFIG_SYS_I2C_EEPROM_TWR is better?

• defining this will override the default write cycle time
  

the default eeprom write cycle time ...

• 5ms which is the default for AT24C01/02/4/08/16. If the
  

• slowest I2C device has different write cycle time, this
  

• option should be defined. The unit is microsecond.
  

• SPI Support: CONFIG_SPI

  Enables SPI driver (so far only tested with

diff --git a/drivers/i2c/fsl_i2c.c b/drivers/i2c/fsl_i2c.c index cb13dee..d192b2a 100644 --- a/drivers/i2c/fsl_i2c.c +++ b/drivers/i2c/fsl_i2c.c @@ -42,6 +42,14 @@ #define CONFIG_I2C_TIMEOUT 10000 #endif

+/*

• • tWR is the write cycle time for EEPROM device
• • in microseconds
• */

+#ifndef CONFIG_I2C_TWR +#define CONFIG_I2C_TWR 5000 +#endif

#define I2C_READ_BIT 1 #define I2C_WRITE_BIT 0

@@ -416,6 +424,7 @@ i2c_write(u8 dev, uint addr, int alen, u8 *data, int length) if (i2c_wait4bus()) /* Wait until STOP */ debug("i2c_write: wait4bus timed out\n");

• udelay(CONFIG_I2C_TWR); if (i == length) return 0;

Hmm.. you add this timeout in the i2c driver, which will result in adding this default 5 ms delay for *all* i2c writes, not only for eeprom devices ... why you didn;t add this timeout in cmd_eeprom, where it seems to me is the better place for it? Looking in this common/cmd_eeprom.c there is a CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS define ... is this not adequate?

bye, Heiko