Re: [PATCH] sparc64/pci_sun4v: fix ATU checks for large DMA masks

[Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>]

Dave, are you going to pick this up through the sparc tree, or do
you expect me to send it through the dma-mapping one?

On Thu, Apr 04, 2019 at 06:25:38PM +0200, Christoph Hellwig wrote:
> Now that we allow drivers to always need to set larger than required
> DMA masks we need to be a little more careful in the sun4v PCI iommu
> driver to chose when to select the ATU support - a larger DMA mask
> can be set even when the platform does not support ATU, so we always
> have to check if it is avaiable before using it.  Add a little helper
> for that and use it in all the places where we make ATU usage decisions
> based on the DMA mask.
> 
> Fixes: 24132a419c68 ("sparc64/pci_sun4v: allow large DMA masks")
> Reported-by: Meelis Roos <mroos-Y27EyoLml9s@public.gmane.org>
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> Tested-by: Meelis Roos <mroos-Y27EyoLml9s@public.gmane.org>
> ---
>  arch/sparc/kernel/pci_sun4v.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
> index a8af6023c126..14b93c5564e3 100644
> --- a/arch/sparc/kernel/pci_sun4v.c
> +++ b/arch/sparc/kernel/pci_sun4v.c
> @@ -73,6 +73,11 @@ static inline void iommu_batch_start(struct device *dev, unsigned long prot, uns
>  	p->npages	= 0;
>  }
>  
> +static inline bool iommu_use_atu(struct iommu *iommu, u64 mask)
> +{
> +	return iommu->atu && mask > DMA_BIT_MASK(32);
> +}
> +
>  /* Interrupts must be disabled.  */
>  static long iommu_batch_flush(struct iommu_batch *p, u64 mask)
>  {
> @@ -92,7 +97,7 @@ static long iommu_batch_flush(struct iommu_batch *p, u64 mask)
>  		prot &= (HV_PCI_MAP_ATTR_READ | HV_PCI_MAP_ATTR_WRITE);
>  
>  	while (npages != 0) {
> -		if (mask <= DMA_BIT_MASK(32) || !pbm->iommu->atu) {
> +		if (!iommu_use_atu(pbm->iommu, mask)) {
>  			num = pci_sun4v_iommu_map(devhandle,
>  						  HV_PCI_TSBID(0, entry),
>  						  npages,
> @@ -179,7 +184,6 @@ static void *dma_4v_alloc_coherent(struct device *dev, size_t size,
>  	unsigned long flags, order, first_page, npages, n;
>  	unsigned long prot = 0;
>  	struct iommu *iommu;
> -	struct atu *atu;
>  	struct iommu_map_table *tbl;
>  	struct page *page;
>  	void *ret;
> @@ -205,13 +209,11 @@ static void *dma_4v_alloc_coherent(struct device *dev, size_t size,
>  	memset((char *)first_page, 0, PAGE_SIZE << order);
>  
>  	iommu = dev->archdata.iommu;
> -	atu = iommu->atu;
> -
>  	mask = dev->coherent_dma_mask;
> -	if (mask <= DMA_BIT_MASK(32) || !atu)
> +	if (!iommu_use_atu(iommu, mask))
>  		tbl = &iommu->tbl;
>  	else
> -		tbl = &atu->tbl;
> +		tbl = &iommu->atu->tbl;
>  
>  	entry = iommu_tbl_range_alloc(dev, tbl, npages, NULL,
>  				      (unsigned long)(-1), 0);
> @@ -333,7 +335,7 @@ static void dma_4v_free_coherent(struct device *dev, size_t size, void *cpu,
>  	atu = iommu->atu;
>  	devhandle = pbm->devhandle;
>  
> -	if (dvma <= DMA_BIT_MASK(32)) {
> +	if (!iommu_use_atu(iommu, dvma)) {
>  		tbl = &iommu->tbl;
>  		iotsb_num = 0; /* we don't care for legacy iommu */
>  	} else {
> @@ -374,7 +376,7 @@ static dma_addr_t dma_4v_map_page(struct device *dev, struct page *page,
>  	npages >>= IO_PAGE_SHIFT;
>  
>  	mask = *dev->dma_mask;
> -	if (mask <= DMA_BIT_MASK(32))
> +	if (!iommu_use_atu(iommu, mask))
>  		tbl = &iommu->tbl;
>  	else
>  		tbl = &atu->tbl;
> @@ -510,7 +512,7 @@ static int dma_4v_map_sg(struct device *dev, struct scatterlist *sglist,
>  				  IO_PAGE_SIZE) >> IO_PAGE_SHIFT;
>  
>  	mask = *dev->dma_mask;
> -	if (mask <= DMA_BIT_MASK(32))
> +	if (!iommu_use_atu(iommu, mask))
>  		tbl = &iommu->tbl;
>  	else
>  		tbl = &atu->tbl;
> -- 
> 2.20.1
> 
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