[flashrom] [PATCH] Partial writes for SPI

Carl-Daniel Hailfinger c-d.hailfinger.devel.2006 at gmx.net
Fri Jul 9 23:57:33 CEST 2010


Hi Michael,

On 22.05.2010 01:38, Carl-Daniel Hailfinger wrote:
> On 25.03.2010 10:46, Michael Karcher wrote:
>   
>> Am Donnerstag, den 25.03.2010, 03:10 +0100 schrieb Carl-Daniel
>> Hailfinger:
>>   
>>     
>>> +	/* Warning: This loop has a very unusual condition and body.
>>> +	 * The loop needs to go through each page with at least one affected
>>> +	 * byte. The lowest page number is (start / page_size) since that
>>> +	 * division rounds down. The highest page number we want is the page
>>> +	 * where the last byte of the range lives. That last byte has the
>>> +	 * address (start + len - 1), thus the highest page number is
>>> +	 * (start + len - 1) / page_size. Since we want to include that last
>>> +	 * page as well, the loop condition uses <=.
>>> +	 */
>>> +	for (i = start / page_size; i <= (start + len - 1) / page_size; i++) {
>>> +		/* Byte position of the first byte in the range in this page. */
>>> +		/* starthere is an offset to the base address of the chip. */
>>> +		starthere = max(start, i * page_size);
>>> +		/* Length of bytes in the range in this page. */
>>> +		lenhere = min(start + len, (i + 1) * page_size) - starthere;
>>> +		for (j = 0; j < lenhere; j += chunksize) {
>>> +			towrite = min(chunksize, lenhere - j);
>>> +			rc = spi_nbyte_program(starthere + j, buf + starthere - start + j, towrite);
>>> +			if (rc)
>>> +				break;
>>> +			while (spi_read_status_register() & JEDEC_RDSR_BIT_WIP)
>>> +				programmer_delay(10);
>>> +		}
>>> +		if (rc)
>>> +			break;
>>> +	}
>>>     
>>>       
>> i would write this as (carful, untested):
>>
>>     startofs = start % pagesize;  /* offset relative to page begin */
>>     /* iterate over all pages to write */
>>     for(pageaddr = start - startofs; pageaddr < start + len; 
>>         pageaddr += page_size) {
>>         endofs = min(pagesize, start + len - pageaddr);
>>         /* iterate over chunks in this page */
>>         for(j = startofs; j < endofs; j += chunksize) {
>>             towrite = min(chunksize, endofs - j);
>>             rc = spi_nbyte_program(pageaddr + j, buf, towrite);
>>             buf += towrite;
>>             if (rc)
>>                 goto leave_page_loop;
>>             /* Copy/paste wait here */
>>         }
>>         startofs = 0;  /* all pages but the first need to be programmed
>>                           from the beginning */
>>     }
>> leave_page_loop:
>>   
>>     
>
> If you could send your code as patch for spi_read_chunked and
> spi_write_chunked, I'd be really happy.
>
>
>   
>> Your logic seem right, too, so this is a matter of taste. I think my
>> version needs less explanation, that's why I would prefer it that way.
>>   
>>     
>
> Fully agreed. We want your logic.
>   

Could you send your logic as a patch which changes spi_read_chunked and
spi_write_chunked?

Thanks!

Regards,
Carl-Daniel

-- 
http://www.hailfinger.org/





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