Re: Failed to disable WCE for a SATA disk

[John Garry <john.garry@huawei.com>]

On 13/01/2020 03:30, chenxiang (M) wrote:

+ Jason

> 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
>>
>>
>>
>>
>> .
>>
> 
> 
> .