[U-Boot] [PATCH] cmd_i2c: Provide option for bulk 'i2c write' in one transaction

[Lubomir Popov]

Hi Heiko,

> Hello Lubomir,
>
> Am 24.11.2014 17:00, schrieb Lubomir Popov:
>> I2C chips do exist that require a write of some multi-byte data to occur in
>> a single bus transaction (aka atomic transfer), otherwise either the write
>> does not come into effect at all, or normal operation of internal circuitry
>> cannot be guaranteed. The current implementation of the 'i2c write' command
>> (transfer of multiple bytes from a memory buffer) in fact performs a separate
>> transaction for each byte to be written and thus cannot support such types of
>> I2C slave devices.
>>
>> This patch provides an alternative by allowing 'i2c write' to execute the
>> write transfer of the given number of bytes in a single bus transaction if
>> CONFIG_SYS_I2C_BULK_WRITE is defined in the board header (otherwise the old
>> method shall compile).
>>
>> Signed-off-by: Lubomir Popov <l-popov at ti.com>
>> ---
>>   common/cmd_i2c.c |   15 ++++++++++++++-
>>   1 file changed, 14 insertions(+), 1 deletion(-)
>
> Could you rebase your patch against current mainline, please?
> As we have now DM in i2c subsystem your patch does not apply clean
> anymore ... thanks!

It looks like you are referring V1 of the patch here. The correct
version is V2 (http://patchwork.ozlabs.org/patch/415117/). If it
doesn't apply as well, I shall try to find some time to fix it.

Thanks,
Lubo

>
> bye,
> Heiko
>>
>> diff --git a/common/cmd_i2c.c b/common/cmd_i2c.c
>> index 3a75f94..7116458 100644
>> --- a/common/cmd_i2c.c
>> +++ b/common/cmd_i2c.c
>> @@ -280,10 +280,22 @@ static int do_i2c_write(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[
>>   		return cmd_usage(cmdtp);
>>
>>   	/*
>> -	 * Length is the number of objects, not number of bytes.
>> +	 * Length is the number of bytes.
>>   	 */
>>   	length = simple_strtoul(argv[4], NULL, 16);
>>
>> +#if defined(CONFIG_SYS_I2C_BULK_WRITE)
>> +	/*
>> +	 * Write all bytes in a single I2C transaction. If the target
>> +	 * device is an EEPROM, it is your responsibility to not cross
>> +	 * a page bounady.
>> +	 */
>> +	if (i2c_write(chip, devaddr, alen, memaddr, length) != 0) {
>> +		puts("Error writing to the chip.\n");
>> +		return 1;
>> +	}
>> +#else
>> +	/* Perform <length> separate write transactions of one byte each */
>>   	while (length-- > 0) {
>>   		if (i2c_write(chip, devaddr++, alen, memaddr++, 1) != 0) {
>>   			puts("Error writing to the chip.\n");
>> @@ -296,6 +308,7 @@ static int do_i2c_write(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[
>>   		udelay(11000);
>>   #endif
>>   	}
>> +#endif
>>   	return 0;
>>   }
>>
>
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