| Message ID | 20210318225632.2481291-1-jollys@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] scsi: libsas: Reset num_scatter if libata mark qc as NODATA | expand |
在 2021/3/19 6:56, Jolly Shah 写道: > When the cache_type for the scsi device is changed, the scsi layer > issues a MODE_SELECT command. The caching mode details are communicated > via a request buffer associated with the scsi command with data > direction set as DMA_TO_DEVICE (scsi_mode_select). When this command > reaches the libata layer, as a part of generic initial setup, libata > layer sets up the scatterlist for the command using the scsi command > (ata_scsi_qc_new). This command is then translated by the libata layer > into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer > treats this as a non data command (ata_mselect_caching), since it only > needs an ata taskfile to pass the caching on/off information to the > device. It does not need the scatterlist that has been setup, so it does > not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately, > when this command reaches the libsas layer(sas_ata_qc_issue), libsas > layer sees it as a non data command with a scatterlist. It cannot > extract the correct dma length, since the scatterlist has not been > mapped with dma_map_sg for a DMA operation. When this partially > constructed SAS task reaches pm80xx LLDD, it results in below warning. > > "pm80xx_chip_sata_req 6058: The sg list address > start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff > end_addr_low=0xffffffff has crossed 4G boundary" > > This patch updates code to handle ata non data commands separately so > num_scatter and total_xfer_len remain 0. > > Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA") > Signed-off-by: Jolly Shah <jollys@google.com> > --- > v2: > - reorganized code to avoid setting num_scatter twice > > drivers/scsi/libsas/sas_ata.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c > index 024e5a550759..8b9a39077dba 100644 > --- a/drivers/scsi/libsas/sas_ata.c > +++ b/drivers/scsi/libsas/sas_ata.c > @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc) > memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len); > task->total_xfer_len = qc->nbytes; > task->num_scatter = qc->n_elem; > + task->data_dir = qc->dma_dir; > + } else if (qc->tf.protocol == ATA_PROT_NODATA) { > + task->data_dir = DMA_NONE; Hi Jolly & John, We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE? Thanks, Jason > } else { > for_each_sg(qc->sg, sg, qc->n_elem, si) > xfer += sg_dma_len(sg); > > task->total_xfer_len = xfer; > task->num_scatter = si; > - } > - > - if (qc->tf.protocol == ATA_PROT_NODATA) > - task->data_dir = DMA_NONE; > - else > task->data_dir = qc->dma_dir; > + } > task->scatter = qc->sg; > task->ata_task.retry_count = 1; > task->task_state_flags = SAS_TASK_STATE_PENDING; >
On 19/03/2021 01:43, Jason Yan wrote: > > > 在 2021/3/19 6:56, Jolly Shah 写道: >> When the cache_type for the scsi device is changed, the scsi layer >> issues a MODE_SELECT command. The caching mode details are communicated >> via a request buffer associated with the scsi command with data >> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command >> reaches the libata layer, as a part of generic initial setup, libata >> layer sets up the scatterlist for the command using the scsi command >> (ata_scsi_qc_new). This command is then translated by the libata layer >> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer >> treats this as a non data command (ata_mselect_caching), since it only >> needs an ata taskfile to pass the caching on/off information to the >> device. It does not need the scatterlist that has been setup, so it does >> not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately, >> when this command reaches the libsas layer(sas_ata_qc_issue), libsas >> layer sees it as a non data command with a scatterlist. It cannot >> extract the correct dma length, since the scatterlist has not been >> mapped with dma_map_sg for a DMA operation. When this partially >> constructed SAS task reaches pm80xx LLDD, it results in below warning. >> >> "pm80xx_chip_sata_req 6058: The sg list address >> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff >> end_addr_low=0xffffffff has crossed 4G boundary" >> >> This patch updates code to handle ata non data commands separately so >> num_scatter and total_xfer_len remain 0. >> >> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata >> marks qc as NODATA") >> Signed-off-by: Jolly Shah <jollys@google.com> Reviewed-by: John Garry <john.garry@huawei.com> @luojiaxing, can you please test this? >> --- >> v2: >> - reorganized code to avoid setting num_scatter twice >> >> drivers/scsi/libsas/sas_ata.c | 9 ++++----- >> 1 file changed, 4 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/scsi/libsas/sas_ata.c >> b/drivers/scsi/libsas/sas_ata.c >> index 024e5a550759..8b9a39077dba 100644 >> --- a/drivers/scsi/libsas/sas_ata.c >> +++ b/drivers/scsi/libsas/sas_ata.c >> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct >> ata_queued_cmd *qc) >> memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len); >> task->total_xfer_len = qc->nbytes; >> task->num_scatter = qc->n_elem; >> + task->data_dir = qc->dma_dir; >> + } else if (qc->tf.protocol == ATA_PROT_NODATA) { >> + task->data_dir = DMA_NONE; > > Hi Jolly & John, > > We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why > ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE? So we can see something like atapi_eh_tur() -> ata_exec_internal(), which is a ATAPI NONDATA and has DMA_NONE, so should be ok. Other cases, like those using the xlate function on the qc for ATA_PROT_NCQ_NODATA, could be checked further. For now, we're just trying to fix the fix. > > Thanks, > Jason > > >> } else { >> for_each_sg(qc->sg, sg, qc->n_elem, si) >> xfer += sg_dma_len(sg); >> task->total_xfer_len = xfer; >> task->num_scatter = si; >> - } >> - >> - if (qc->tf.protocol == ATA_PROT_NODATA) >> - task->data_dir = DMA_NONE; >> - else >> task->data_dir = qc->dma_dir; >> + } >> task->scatter = qc->sg; >> task->ata_task.retry_count = 1; >> task->task_state_flags = SAS_TASK_STATE_PENDING; >> > .
On 2021/3/20 20:14, John Garry wrote: > On 19/03/2021 01:43, Jason Yan wrote: >> >> >> 在 2021/3/19 6:56, Jolly Shah 写道: >>> When the cache_type for the scsi device is changed, the scsi layer >>> issues a MODE_SELECT command. The caching mode details are communicated >>> via a request buffer associated with the scsi command with data >>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command >>> reaches the libata layer, as a part of generic initial setup, libata >>> layer sets up the scatterlist for the command using the scsi command >>> (ata_scsi_qc_new). This command is then translated by the libata layer >>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer >>> treats this as a non data command (ata_mselect_caching), since it only >>> needs an ata taskfile to pass the caching on/off information to the >>> device. It does not need the scatterlist that has been setup, so it >>> does >>> not perform dma_map_sg on the scatterlist (ata_qc_issue). >>> Unfortunately, >>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas >>> layer sees it as a non data command with a scatterlist. It cannot >>> extract the correct dma length, since the scatterlist has not been >>> mapped with dma_map_sg for a DMA operation. When this partially >>> constructed SAS task reaches pm80xx LLDD, it results in below warning. >>> >>> "pm80xx_chip_sata_req 6058: The sg list address >>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff >>> end_addr_low=0xffffffff has crossed 4G boundary" >>> >>> This patch updates code to handle ata non data commands separately so >>> num_scatter and total_xfer_len remain 0. >>> >>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if >>> libata marks qc as NODATA") >>> Signed-off-by: Jolly Shah <jollys@google.com> > > Reviewed-by: John Garry <john.garry@huawei.com> > > @luojiaxing, can you please test this? Sure, let me take a look, and reply the test result here later Thanks Jiaxing > >>> --- >>> v2: >>> - reorganized code to avoid setting num_scatter twice >>> >>> drivers/scsi/libsas/sas_ata.c | 9 ++++----- >>> 1 file changed, 4 insertions(+), 5 deletions(-) >>> >>> diff --git a/drivers/scsi/libsas/sas_ata.c >>> b/drivers/scsi/libsas/sas_ata.c >>> index 024e5a550759..8b9a39077dba 100644 >>> --- a/drivers/scsi/libsas/sas_ata.c >>> +++ b/drivers/scsi/libsas/sas_ata.c >>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct >>> ata_queued_cmd *qc) >>> memcpy(task->ata_task.atapi_packet, qc->cdb, >>> qc->dev->cdb_len); >>> task->total_xfer_len = qc->nbytes; >>> task->num_scatter = qc->n_elem; >>> + task->data_dir = qc->dma_dir; >>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) { >>> + task->data_dir = DMA_NONE; >> >> Hi Jolly & John, >> >> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why >> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE? > > So we can see something like atapi_eh_tur() -> ata_exec_internal(), > which is a ATAPI NONDATA and has DMA_NONE, so should be ok. > > Other cases, like those using the xlate function on the qc for > ATA_PROT_NCQ_NODATA, could be checked further. > > For now, we're just trying to fix the fix. > >> >> Thanks, >> Jason >> >> >>> } else { >>> for_each_sg(qc->sg, sg, qc->n_elem, si) >>> xfer += sg_dma_len(sg); >>> task->total_xfer_len = xfer; >>> task->num_scatter = si; >>> - } >>> - >>> - if (qc->tf.protocol == ATA_PROT_NODATA) >>> - task->data_dir = DMA_NONE; >>> - else >>> task->data_dir = qc->dma_dir; >>> + } >>> task->scatter = qc->sg; >>> task->ata_task.retry_count = 1; >>> task->task_state_flags = SAS_TASK_STATE_PENDING; >>> >> . > > > . >
Hi Luojiaxing, On Mon, Mar 22, 2021 at 1:41 AM luojiaxing <luojiaxing@huawei.com> wrote: > > > On 2021/3/20 20:14, John Garry wrote: > > On 19/03/2021 01:43, Jason Yan wrote: > >> > >> > >> 在 2021/3/19 6:56, Jolly Shah 写道: > >>> When the cache_type for the scsi device is changed, the scsi layer > >>> issues a MODE_SELECT command. The caching mode details are communicated > >>> via a request buffer associated with the scsi command with data > >>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command > >>> reaches the libata layer, as a part of generic initial setup, libata > >>> layer sets up the scatterlist for the command using the scsi command > >>> (ata_scsi_qc_new). This command is then translated by the libata layer > >>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer > >>> treats this as a non data command (ata_mselect_caching), since it only > >>> needs an ata taskfile to pass the caching on/off information to the > >>> device. It does not need the scatterlist that has been setup, so it > >>> does > >>> not perform dma_map_sg on the scatterlist (ata_qc_issue). > >>> Unfortunately, > >>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas > >>> layer sees it as a non data command with a scatterlist. It cannot > >>> extract the correct dma length, since the scatterlist has not been > >>> mapped with dma_map_sg for a DMA operation. When this partially > >>> constructed SAS task reaches pm80xx LLDD, it results in below warning. > >>> > >>> "pm80xx_chip_sata_req 6058: The sg list address > >>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff > >>> end_addr_low=0xffffffff has crossed 4G boundary" > >>> > >>> This patch updates code to handle ata non data commands separately so > >>> num_scatter and total_xfer_len remain 0. > >>> > >>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if > >>> libata marks qc as NODATA") > >>> Signed-off-by: Jolly Shah <jollys@google.com> > > > > Reviewed-by: John Garry <john.garry@huawei.com> > > > > @luojiaxing, can you please test this? > > > Sure, let me take a look, and reply the test result here later > Wanted to follow up on test results. Any updates? Thanks, Jolly > > Thanks > > Jiaxing > > > > > >>> --- > >>> v2: > >>> - reorganized code to avoid setting num_scatter twice > >>> > >>> drivers/scsi/libsas/sas_ata.c | 9 ++++----- > >>> 1 file changed, 4 insertions(+), 5 deletions(-) > >>> > >>> diff --git a/drivers/scsi/libsas/sas_ata.c > >>> b/drivers/scsi/libsas/sas_ata.c > >>> index 024e5a550759..8b9a39077dba 100644 > >>> --- a/drivers/scsi/libsas/sas_ata.c > >>> +++ b/drivers/scsi/libsas/sas_ata.c > >>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct > >>> ata_queued_cmd *qc) > >>> memcpy(task->ata_task.atapi_packet, qc->cdb, > >>> qc->dev->cdb_len); > >>> task->total_xfer_len = qc->nbytes; > >>> task->num_scatter = qc->n_elem; > >>> + task->data_dir = qc->dma_dir; > >>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) { > >>> + task->data_dir = DMA_NONE; > >> > >> Hi Jolly & John, > >> > >> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why > >> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE? > > > > So we can see something like atapi_eh_tur() -> ata_exec_internal(), > > which is a ATAPI NONDATA and has DMA_NONE, so should be ok. > > > > Other cases, like those using the xlate function on the qc for > > ATA_PROT_NCQ_NODATA, could be checked further. > > > > For now, we're just trying to fix the fix. > > > >> > >> Thanks, > >> Jason > >> > >> > >>> } else { > >>> for_each_sg(qc->sg, sg, qc->n_elem, si) > >>> xfer += sg_dma_len(sg); > >>> task->total_xfer_len = xfer; > >>> task->num_scatter = si; > >>> - } > >>> - > >>> - if (qc->tf.protocol == ATA_PROT_NODATA) > >>> - task->data_dir = DMA_NONE; > >>> - else > >>> task->data_dir = qc->dma_dir; > >>> + } > >>> task->scatter = qc->sg; > >>> task->ata_task.retry_count = 1; > >>> task->task_state_flags = SAS_TASK_STATE_PENDING; > >>> > >> . > > > > > > . > > >
On 2021/4/2 6:34, Jolly Shah wrote: > Hi Luojiaxing, > > > On Mon, Mar 22, 2021 at 1:41 AM luojiaxing <luojiaxing@huawei.com> wrote: >> >> On 2021/3/20 20:14, John Garry wrote: >>> On 19/03/2021 01:43, Jason Yan wrote: >>>> >>>> 在 2021/3/19 6:56, Jolly Shah 写道: >>>>> When the cache_type for the scsi device is changed, the scsi layer >>>>> issues a MODE_SELECT command. The caching mode details are communicated >>>>> via a request buffer associated with the scsi command with data >>>>> direction set as DMA_TO_DEVICE (scsi_mode_select). When this command >>>>> reaches the libata layer, as a part of generic initial setup, libata >>>>> layer sets up the scatterlist for the command using the scsi command >>>>> (ata_scsi_qc_new). This command is then translated by the libata layer >>>>> into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer >>>>> treats this as a non data command (ata_mselect_caching), since it only >>>>> needs an ata taskfile to pass the caching on/off information to the >>>>> device. It does not need the scatterlist that has been setup, so it >>>>> does >>>>> not perform dma_map_sg on the scatterlist (ata_qc_issue). >>>>> Unfortunately, >>>>> when this command reaches the libsas layer(sas_ata_qc_issue), libsas >>>>> layer sees it as a non data command with a scatterlist. It cannot >>>>> extract the correct dma length, since the scatterlist has not been >>>>> mapped with dma_map_sg for a DMA operation. When this partially >>>>> constructed SAS task reaches pm80xx LLDD, it results in below warning. >>>>> >>>>> "pm80xx_chip_sata_req 6058: The sg list address >>>>> start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff >>>>> end_addr_low=0xffffffff has crossed 4G boundary" >>>>> >>>>> This patch updates code to handle ata non data commands separately so >>>>> num_scatter and total_xfer_len remain 0. >>>>> >>>>> Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if >>>>> libata marks qc as NODATA") >>>>> Signed-off-by: Jolly Shah <jollys@google.com> >>> Reviewed-by: John Garry <john.garry@huawei.com> >>> >>> @luojiaxing, can you please test this? >> >> Sure, let me take a look, and reply the test result here later >> > Wanted to follow up on test results. Any updates? Sorry for reply to you so late. I use sdparm to change cache type of SATA disk, and it's ok with my test. In addition, some other functional tests result have no problem too, So I think this patch is ok to me. Tested-by: Luo Jiaxing <luojiaxing@huawei.com> Thanks Jiaxing > > Thanks, > Jolly > >> Thanks >> >> Jiaxing >> >> >>>>> --- >>>>> v2: >>>>> - reorganized code to avoid setting num_scatter twice >>>>> >>>>> drivers/scsi/libsas/sas_ata.c | 9 ++++----- >>>>> 1 file changed, 4 insertions(+), 5 deletions(-) >>>>> >>>>> diff --git a/drivers/scsi/libsas/sas_ata.c >>>>> b/drivers/scsi/libsas/sas_ata.c >>>>> index 024e5a550759..8b9a39077dba 100644 >>>>> --- a/drivers/scsi/libsas/sas_ata.c >>>>> +++ b/drivers/scsi/libsas/sas_ata.c >>>>> @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct >>>>> ata_queued_cmd *qc) >>>>> memcpy(task->ata_task.atapi_packet, qc->cdb, >>>>> qc->dev->cdb_len); >>>>> task->total_xfer_len = qc->nbytes; >>>>> task->num_scatter = qc->n_elem; >>>>> + task->data_dir = qc->dma_dir; >>>>> + } else if (qc->tf.protocol == ATA_PROT_NODATA) { >>>>> + task->data_dir = DMA_NONE; >>>> Hi Jolly & John, >>>> >>>> We only set DMA_NONE for ATA_PROT_NODATA, I'm curious about why >>>> ATA_PROT_NCQ_NODATA and ATAPI_PROT_NODATA do not need to set DMA_NONE? >>> So we can see something like atapi_eh_tur() -> ata_exec_internal(), >>> which is a ATAPI NONDATA and has DMA_NONE, so should be ok. >>> >>> Other cases, like those using the xlate function on the qc for >>> ATA_PROT_NCQ_NODATA, could be checked further. >>> >>> For now, we're just trying to fix the fix. >>> >>>> Thanks, >>>> Jason >>>> >>>> >>>>> } else { >>>>> for_each_sg(qc->sg, sg, qc->n_elem, si) >>>>> xfer += sg_dma_len(sg); >>>>> task->total_xfer_len = xfer; >>>>> task->num_scatter = si; >>>>> - } >>>>> - >>>>> - if (qc->tf.protocol == ATA_PROT_NODATA) >>>>> - task->data_dir = DMA_NONE; >>>>> - else >>>>> task->data_dir = qc->dma_dir; >>>>> + } >>>>> task->scatter = qc->sg; >>>>> task->ata_task.retry_count = 1; >>>>> task->task_state_flags = SAS_TASK_STATE_PENDING; >>>>> >>>> . >>> >>> . >>> > . >
On Thu, 18 Mar 2021 15:56:32 -0700, Jolly Shah wrote: > When the cache_type for the scsi device is changed, the scsi layer > issues a MODE_SELECT command. The caching mode details are communicated > via a request buffer associated with the scsi command with data > direction set as DMA_TO_DEVICE (scsi_mode_select). When this command > reaches the libata layer, as a part of generic initial setup, libata > layer sets up the scatterlist for the command using the scsi command > (ata_scsi_qc_new). This command is then translated by the libata layer > into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer > treats this as a non data command (ata_mselect_caching), since it only > needs an ata taskfile to pass the caching on/off information to the > device. It does not need the scatterlist that has been setup, so it does > not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately, > when this command reaches the libsas layer(sas_ata_qc_issue), libsas > layer sees it as a non data command with a scatterlist. It cannot > extract the correct dma length, since the scatterlist has not been > mapped with dma_map_sg for a DMA operation. When this partially > constructed SAS task reaches pm80xx LLDD, it results in below warning. > > [...] Applied to 5.12/scsi-fixes, thanks! [1/1] scsi: libsas: Reset num_scatter if libata mark qc as NODATA https://git.kernel.org/mkp/scsi/c/176ddd89171d -- Martin K. Petersen Oracle Linux Engineering
diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c index 024e5a550759..8b9a39077dba 100644 --- a/drivers/scsi/libsas/sas_ata.c +++ b/drivers/scsi/libsas/sas_ata.c @@ -201,18 +201,17 @@ static unsigned int sas_ata_qc_issue(struct ata_queued_cmd *qc) memcpy(task->ata_task.atapi_packet, qc->cdb, qc->dev->cdb_len); task->total_xfer_len = qc->nbytes; task->num_scatter = qc->n_elem; + task->data_dir = qc->dma_dir; + } else if (qc->tf.protocol == ATA_PROT_NODATA) { + task->data_dir = DMA_NONE; } else { for_each_sg(qc->sg, sg, qc->n_elem, si) xfer += sg_dma_len(sg); task->total_xfer_len = xfer; task->num_scatter = si; - } - - if (qc->tf.protocol == ATA_PROT_NODATA) - task->data_dir = DMA_NONE; - else task->data_dir = qc->dma_dir; + } task->scatter = qc->sg; task->ata_task.retry_count = 1; task->task_state_flags = SAS_TASK_STATE_PENDING;
When the cache_type for the scsi device is changed, the scsi layer issues a MODE_SELECT command. The caching mode details are communicated via a request buffer associated with the scsi command with data direction set as DMA_TO_DEVICE (scsi_mode_select). When this command reaches the libata layer, as a part of generic initial setup, libata layer sets up the scatterlist for the command using the scsi command (ata_scsi_qc_new). This command is then translated by the libata layer into ATA_CMD_SET_FEATURES (ata_scsi_mode_select_xlat). The libata layer treats this as a non data command (ata_mselect_caching), since it only needs an ata taskfile to pass the caching on/off information to the device. It does not need the scatterlist that has been setup, so it does not perform dma_map_sg on the scatterlist (ata_qc_issue). Unfortunately, when this command reaches the libsas layer(sas_ata_qc_issue), libsas layer sees it as a non data command with a scatterlist. It cannot extract the correct dma length, since the scatterlist has not been mapped with dma_map_sg for a DMA operation. When this partially constructed SAS task reaches pm80xx LLDD, it results in below warning. "pm80xx_chip_sata_req 6058: The sg list address start_addr=0x0000000000000000 data_len=0x0end_addr_high=0xffffffff end_addr_low=0xffffffff has crossed 4G boundary" This patch updates code to handle ata non data commands separately so num_scatter and total_xfer_len remain 0. Fixes: 53de092f47ff ("scsi: libsas: Set data_dir as DMA_NONE if libata marks qc as NODATA") Signed-off-by: Jolly Shah <jollys@google.com> --- v2: - reorganized code to avoid setting num_scatter twice drivers/scsi/libsas/sas_ata.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)