| Message ID | cover.1460048991.git.robin.murphy@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Apr 07, 2016 at 06:42:03PM +0100, Robin Murphy wrote: > Hi all, Hi Robin, > Since this area seems to be in vogue at the moment, here's what I was > working on when the related patches[1][2] popped up, which happens to > be more or less the intersection of both. As I recycled some of Will's > old series as a starting point, I've retained the cleanup patches from > that with their original acks - hope that's OK. > > Fortunately, this already looks rather like parts of Joerg's plan[3], > so I hope it's a suitable first step. Below is a quick hacked-up example > of the kind of caller-controlled special use-case alluded to, using the > SMMU/HDLCD combo on Juno - for a 'real' implementation of this we'd want > the group-based domain allocation call so the driver could throw the > device at that and get its own non-default DMA ops domain to play with. I like this series a lot and it moves us a significant step closer to being able to request specific IOMMU geometry at domain initialisation time. For the series: Acked-by: Will Deacon <will.deacon@arm.com> Will
On Thu, Apr 07, 2016 at 06:42:03PM +0100, Robin Murphy wrote: > Hi all, > > Since this area seems to be in vogue at the moment, here's what I was > working on when the related patches[1][2] popped up, which happens to > be more or less the intersection of both. As I recycled some of Will's > old series as a starting point, I've retained the cleanup patches from > that with their original acks - hope that's OK. > > Fortunately, this already looks rather like parts of Joerg's plan[3], > so I hope it's a suitable first step. Below is a quick hacked-up example > of the kind of caller-controlled special use-case alluded to, using the > SMMU/HDLCD combo on Juno - for a 'real' implementation of this we'd want > the group-based domain allocation call so the driver could throw the > device at that and get its own non-default DMA ops domain to play with. > > Robin. > > [1]:http://thread.gmane.org/gmane.linux.kernel.iommu/12774 > [2]:http://thread.gmane.org/gmane.linux.kernel.iommu/12901 > [3]:http://article.gmane.org/gmane.linux.kernel.iommu/12937 > > Robin Murphy (4): > iommu: of: enforce const-ness of struct iommu_ops > iommu: Allow selecting page sizes per domain > iommu/dma: Finish optimising higher-order allocations > iommu/arm-smmu: Use per-domain page sizes. > > Will Deacon (1): > iommu: remove unused priv field from struct iommu_ops Okay, I am still no happy that this lifts the requirements of the iommu-api for the arm-smmu driver. But to get there we need more core changes and this code is a step in the right direction, so I applied it. Thanks, Joerg
diff --git a/drivers/gpu/drm/arm/hdlcd_drv.c b/drivers/gpu/drm/arm/hdlcd_drv.c index 56b829f..0da0f4b 100644 --- a/drivers/gpu/drm/arm/hdlcd_drv.c +++ b/drivers/gpu/drm/arm/hdlcd_drv.c @@ -13,6 +13,7 @@ #include <linux/spinlock.h> #include <linux/clk.h> #include <linux/component.h> +#include <linux/iommu.h> #include <linux/list.h> #include <linux/of_graph.h> #include <linux/of_reserved_mem.h> @@ -34,6 +35,7 @@ static int hdlcd_load(struct drm_device *drm, unsigned long flags) { struct hdlcd_drm_private *hdlcd = drm->dev_private; struct platform_device *pdev = to_platform_device(drm->dev); + struct iommu_domain *dom; struct resource *res; u32 version; int ret; @@ -79,6 +81,21 @@ static int hdlcd_load(struct drm_device *drm, unsigned long flags) if (ret) goto setup_fail; + /* + * EXAMPLE: Let's say that if we're using an SMMU, we'd rather waste + * a little memory by forcing DMA allocation and mapping to section + * granularity so the whole buffer fits in the TLBs, than waste power + * by having the SMMU constantly walking page tables all the time we're + * scanning out. In this case we know our default domain isn't shared + * with any other devices, so we can cheat and mangle that directly. + */ + dom = iommu_get_domain_for_dev(drm->dev); + if (dom) { + dom->pgsize_bitmap &= ~(SZ_1M - 1); + if (!dom->pgsize_bitmap) + goto setup_fail; + } + ret = hdlcd_setup_crtc(drm); if (ret < 0) { DRM_ERROR("failed to create crtc\n");