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SubjectRe: [RFC PATCH V2] scsi: ufs: Add specific callback for setting DMA mask
On 2018-05-15 21:31, Alim Akhtar wrote:
> Ping !!!
>
> On Thu, Mar 8, 2018 at 4:33 PM, Alim Akhtar <alim.akhtar@samsung.com>
> 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@samsung.com>
>> ---
>> drivers/scsi/ufs/ufshcd.c | 3 +++
>> drivers/scsi/ufs/ufshcd.h | 2 ++
>> 2 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:
>> - 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);
>> */
>> static int ufshcd_set_dma_mask(struct ufs_hba *hba)
>> {
>> + if (hba->vops && hba->vops->set_dma_mask)
>> + return hba->vops->set_dma_mask(hba);
>> +
>> if (hba->capabilities & MASK_64_ADDRESSING_SUPPORT) {
>> if (!dma_set_mask_and_coherent(hba->dev,
>> DMA_BIT_MASK(64)))
>> 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 {
>> * @resume: called during host controller PM callback
>> * @dbg_register_dump: used to dump controller debug information
>> * @phy_initialization: used to initialize phys
>> + * @set_dma_mask: used to set variant specific DMA mask
>> */
>> struct ufs_hba_variant_ops {
>> const char *name;
>> @@ -325,6 +326,7 @@ struct ufs_hba_variant_ops {
>> int (*resume)(struct ufs_hba *, enum ufs_pm_op);
>> void (*dbg_register_dump)(struct ufs_hba *hba);
>> int (*phy_initialization)(struct ufs_hba *);
>> + int (*set_dma_mask)(struct ufs_hba *hba);
>> };
>>
>> /* clock gating state */
>> --
>> 2.7.4
>>

Looks reasonable to me, you may try posting non-RFC version.

--
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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