Re: Failed to disable WCE for a SATA disk

["chenxiang (M)" <chenxiang66@hisilicon.com>]

Hi,

在 2019/12/11 11:21, chenxiang (M) 写道:
> Hi,
>
> I encounter a issue related to libata and libsas. For hisi_sas driver, 
> it uses libsas. When disable WCE with tool sdparm (sdparm --clear=WCE 
> /dev/sda) for a SATA disk,
> it fails with error info from hardware (the error info indicates that 
> the length of transfer data is conflicted with the direction of data, 
> the length is 0 but
> the data of direction is from host to device).
>
> I check the process: When disable WCE, it sends pasthrough IO with 
> sg_io , req->__data_len is not 0, and scsi_cmd->sc_data_direction = 
> DMA_TO_DEVICE.
> But for the command (MODE_SELECT), qc->tf.protocol is set 0 (not 
> ATA_PROT_DMA) in ->queuecommand() 
> ->ata_sas_queuecmd()->ata_scsi_translate()->ata_scsi_mod_select_xlat()->ata_mselect_caching(),
> so it doesn't dma map ata sg in function ata_qc_issue(). While in 
> function sas_ata_qc_issue()，it calcutes the length with the total sum 
> of sg_dma_len(sg), as for the
> command it doesn't dma map ata sg, so the length is 0.
>
> Do we need to dma map ata sg for the command? Or is it really we need 
> the data for the command MODE_SELECT?

Does anyone have idea about it ?

>
> Thanks,
> Shawn
>
>
>
>
> .
>