| Message ID | 20190924150131.24404-1-svens@stackframe.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Headers | show |
| Series | parisc: remove 32-bit DMA enforcement from sba_iommu | expand |
Helge, On Tue, Sep 24, 2019 at 05:01:31PM +0200, Sven Schnelle wrote: > This breaks booting from sata_sil24 with the recent DMA > change. According to James Bottomley this was in to improve > performance. Remove it for now to make DMA working again. > > Signed-off-by: Sven Schnelle <svens@stackframe.org> > --- > drivers/parisc/sba_iommu.c | 8 -------- > 1 file changed, 8 deletions(-) > > diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c > index 296668caf7e5..6ac9500f2752 100644 > --- a/drivers/parisc/sba_iommu.c > +++ b/drivers/parisc/sba_iommu.c > @@ -678,14 +678,6 @@ static int sba_dma_supported( struct device *dev, u64 mask) > return(0); > } > > - /* Documentation/DMA-API-HOWTO.txt tells drivers to try 64-bit > - * first, then fall back to 32-bit if that fails. > - * We are just "encouraging" 32-bit DMA masks here since we can > - * never allow IOMMU bypass unless we add special support for ZX1. > - */ > - if (mask > ~0U) > - return 0; > - > ioc = GET_IOC(dev); > if (!ioc) > return 0; > -- > 2.23.0.rc1 > please drop that patch for now. With 64-bit DMA my C8000 crashes with HPMCs likely caused by invalid DMA transfers. So i have to read up a bit on the DMA capabilites, and what "since we can never allow IOMMU bypass unless we add special support for ZX1" means. The other option is to prepare a patch that limits the DMA mask with the API Christoph mentioned, but i would first like to understand the capabilities of the chipset. Regards Sven
diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c index 296668caf7e5..6ac9500f2752 100644 --- a/drivers/parisc/sba_iommu.c +++ b/drivers/parisc/sba_iommu.c @@ -678,14 +678,6 @@ static int sba_dma_supported( struct device *dev, u64 mask) return(0); } - /* Documentation/DMA-API-HOWTO.txt tells drivers to try 64-bit - * first, then fall back to 32-bit if that fails. - * We are just "encouraging" 32-bit DMA masks here since we can - * never allow IOMMU bypass unless we add special support for ZX1. - */ - if (mask > ~0U) - return 0; - ioc = GET_IOC(dev); if (!ioc) return 0;
This breaks booting from sata_sil24 with the recent DMA change. According to James Bottomley this was in to improve performance. Remove it for now to make DMA working again. Signed-off-by: Sven Schnelle <svens@stackframe.org> --- drivers/parisc/sba_iommu.c | 8 -------- 1 file changed, 8 deletions(-)