Re: Random libata notes

[Tejun Heo <htejun@gmail.com>]

Tejun Heo wrote:
> Jeff Garzik wrote:
> 
>> These are small TODO bits that I didn't want to forget...  Patches 
>> welcome.
>>
>> 1) ATAPI edge case.  Due to adding the padding s/g entry, we must 
>> adjust sg_tablesize to include ' - 1' for each driver
> 
> 
> Isn't this handled by ata_scsi_slave_config()? If the attached device is 
> ATAPI, ata_scsi_slave_config() reduces max_hw_segments by 1. We'll need 
> to increment it back when detaching the device though.
> 
>>
>> 2) ata_scsi_slave_config() hardcodes a call to
>> blk_queue_max_phys_segments(, LIBATA_MAX_PRD), when the value passed
>> should not be so limited on nice hardware like AHCI.

And, AFAICS, we can increase max_phys_segments all we want. This limits 
the number of segments before IOMMU mapping. The only part that's 
affected is the driver (software) and I don't see any limitation in 
libata PIO implementation that puts limitation on the number of sg 
entries. Simply changing LIBATA_MAX_PRD to 65535 should do it.

>>
>> 3) sata_mv: add back SCR_ERR clear?
>>         mv_scr_write(ap, SCR_ERROR, mv_scr_read(ap, SCR_ERROR));
>>
>> 4) sata_mv: set DMA mask
>>

-- 
tejun