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

[Subhash Jadavani]

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>
> > ---
> >  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.

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