On 09/08/2022 15:57, Damien Le Moal wrote:
As far as I can see, this patch should not make a difference unless the
ATA shost driver is setting the max_sectors value unnecessarily low.
For __ATA_BASE_SHT, we don't set max_sectors. As such, we default
shost->max_sectors = SCSI_DEFAULT_MAX_SECTORS (=1024) in
scsi_host_alloc(). I assume no shost dma mapping limit applied.
Then - for example - we could select dev->max_sectors =
ATA_MAX_SECTORS_LBA48 (=65535) in ata_dev_configure().
So with commit 0568e6122574 we would have final max sectors = 1024, as
opposed to 65535 previously. I guess that the problem is something like
this.
If so, it seems that we would need to apply the shost dma mapping limit
separately in ata_scsi_dev_config() and not use shost->max_sectors.
OK. Will have a look at that.
We may need to introduce something like shost->max_hw_sectors, which is
set according to sht max sectors and dma mapping limits. That could be
also used in USB scsiglue slave_configure()
Or else set max_sectors value for __ATA_BASE_SHT, but I don't know a
sane value there considering ATA_MAX_SECTORS_LBA48 gives max_sectors of
65535.
Damien, please let me know if you need help now. I am just waiting for
you to test to prove this theory about dev->max_sectors being capped. I
don't have an AHCI setup readily-available for testing - just SAS cards
or QEMU.
Thanks,
John
