Re: [RFC PATCH V2] scsi: ufs: Add specific callback for setting DMA mask

[Alim Akhtar]

Hi Subhash

On 05/17/2018 03:01 AM, Subhash Jadavani wrote:
> On 2018-05-15 21:31, Alim Akhtar wrote:
>> Ping !!!
>>
>> On Thu, Mar 8, 2018 at 4:33 PM, Alim Akhtar <alim.akhtar@xxxxxxxxxxx> 
>> wrote:
>>> Currently DMA mask for UFS HCI is set by reading CAP register's
>>> [64AS] bit. Some HCI controller like Exynos support 36-bit bus address.
>>> This works perfectly fine with DMA mask set as 64 in case there is no
>>> IOMMU attached to HCI.
>>> In case if HCI is behind an IOMMU, setting DMA mask as 64 bit won't
>>> work as HCI has only 36bit addressing and SMMU has created mapping of
>>> 64 bit and as the device truncates the address, its mapping will not
>>> be found by iommu.
>>> To resolve such issues, let the variant driver sets its own DMA mask.
>>>
>>> Signed-off-by: Alim Akhtar <alim.akhtar@xxxxxxxxxxx>
>>> ---
>>> Âdrivers/scsi/ufs/ufshcd.c | 3 +++
>>> Âdrivers/scsi/ufs/ufshcd.h | 2 ++
>>> Â2 files changed, 5 insertions(+)
>>>
>>> I am not sure if there are other ways available to handle such cases.
>>> The IOMMU I am talking about is arm-smmu and it DT binding does not
>>> give much idea about handling such cases.
>>> Have tested this patch with HCI controller with IOMMU attached.
>>>
>>> Changes Since V1:
>>> ÂÂÂÂÂÂÂ - Fixed build issue as reported by Kbuild test robot.
>>>
>>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
>>> index a355d98..9a1374e 100644
>>> --- a/drivers/scsi/ufs/ufshcd.c
>>> +++ b/drivers/scsi/ufs/ufshcd.c
>>> @@ -7781,6 +7781,9 @@ EXPORT_SYMBOL_GPL(ufshcd_dealloc_host);
>>> Â */
>>> Âstatic int ufshcd_set_dma_mask(struct ufs_hba *hba)
>>> Â{
>>> +ÂÂÂÂÂÂ if (hba->vops && hba->vops->set_dma_mask)
>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return hba->vops->set_dma_mask(hba);
>>> +
>>> ÂÂÂÂÂÂÂ if (hba->capabilities & MASK_64_ADDRESSING_SUPPORT) {
>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (!dma_set_mask_and_coherent(hba->dev, 
>>> DMA_BIT_MASK(64)))
>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return 0;
>>> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
>>> index 1332e54..89c6dae 100644
>>> --- a/drivers/scsi/ufs/ufshcd.h
>>> +++ b/drivers/scsi/ufs/ufshcd.h
>>> @@ -297,6 +297,7 @@ struct ufs_pwr_mode_info {
>>> Â * @resume: called during host controller PM callback
>>> Â * @dbg_register_dump: used to dump controller debug information
>>> Â * @phy_initialization: used to initialize phys
>>> + * @set_dma_mask: used to set variant specific DMA mask
>>> Â */
>>> Âstruct ufs_hba_variant_ops {
>>> ÂÂÂÂÂÂÂ const char *name;
>>> @@ -325,6 +326,7 @@ struct ufs_hba_variant_ops {
>>> ÂÂÂÂÂÂÂ intÂÂÂÂ (*resume)(struct ufs_hba *, enum ufs_pm_op);
>>> ÂÂÂÂÂÂÂ voidÂÂÂ (*dbg_register_dump)(struct ufs_hba *hba);
>>> ÂÂÂÂÂÂÂ intÂÂÂÂ (*phy_initialization)(struct ufs_hba *);
>>> +ÂÂÂÂÂÂ intÂÂÂÂ (*set_dma_mask)(struct ufs_hba *hba);
>>> Â};
>>>
>>> Â/* clock gating state */
>>> -- 
>>> 2.7.4
>>>
> 
> Looks reasonable to me, you may try posting non-RFC version.
> 
Thanks for review.
Will send a non-RFC version.

Regards,
Alim