On 13/06/16 10:56, Shunqian Zheng wrote:
Hi
On 2016年06月10日 17:10, Tomasz Figa wrote:
Hi,
On Wed, Jun 8, 2016 at 10:26 PM, Shunqian Zheng
<zhengsq@xxxxxxxxxxxxxx> wrote:
Use DMA API instead of architecture internal functions like
__cpuc_flush_dcache_area() etc.
To support the virtual device like DRM the virtual slave iommu
added in the previous patch, attaching to which the DRM can use
it own domain->dev for dma_map_*(), dma_sync_*() even VOP is disabled.
With this patch, this driver is available for ARM64 like RK3399.
Could we instead simply allocate coherent memory for page tables using
dma_alloc_coherent() and skip any flushing on CPU side completely? If
I'm looking correctly, the driver only reads back the page directory
when checking if there is a need to allocate new page table, so there
shouldn't be any significant penalty for disabling the cache.
I try to use dma_alloc_coherent() to replace the dma_map_single(),
but it doesn't work for me properly.
Because the DRM uses the iommu_dma_ops instead the swiotlb_dma_ops after
attaching
to iommu, so when the iommu domain need to alloc a new page in
rk_iommu_map(),
it would call:
rk_iommu_map() --> dma_alloc_coherent() --> ops->alloc() -->
iommu_map() --> rk_iommu_map()
That sounds more like you're passing the wrong device around somewhere,
since this approach is working fine for other IOMMUs; specifically, the
flow goes:
dma_alloc_coherent(DRM dev) // for buffer
--> ops->alloc(DRM dev)
--> iommu_dma_alloc(DRM dev)
--> iommu_map()
--> dma_alloc_coherent(IOMMU dev) // for pagetable
--> ops->alloc(IOMMU dev)
--> swiotlb_alloc(IOMMU dev)
There shouldn't be any need for this "virtual IOMMU" at all. I think the
Exynos DRM driver is in a similar situation of having multiple devices
(involving multiple IOMMUs) backing the virtual DRM device, and that
doesn't seem to be doing anything this crazy so it's probably worth
taking a look at.
Robin.
Then I try to reserve memory for coherent so that, dma_alloc_coherent()
calls dma_alloc_from_coherent()
but not ops->alloc(). But it doesn't work too because when DRM request
buffer it never uses iommu.
Other than that, please see some comments inline.
Signed-off-by: Shunqian Zheng <zhengsq@xxxxxxxxxxxxxx>
---
drivers/iommu/rockchip-iommu.c | 113
++++++++++++++++++++++++++---------------
1 file changed, 71 insertions(+), 42 deletions(-)
diff --git a/drivers/iommu/rockchip-iommu.c
b/drivers/iommu/rockchip-iommu.c
index d6c3051..aafea6e 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -4,8 +4,6 @@
* published by the Free Software Foundation.
*/
-#include <asm/cacheflush.h>
-#include <asm/pgtable.h>
#include <linux/compiler.h>
#include <linux/delay.h>
#include <linux/device.h>
@@ -61,8 +59,7 @@
#define RK_MMU_IRQ_BUS_ERROR 0x02 /* bus read error */
#define RK_MMU_IRQ_MASK (RK_MMU_IRQ_PAGE_FAULT |
RK_MMU_IRQ_BUS_ERROR)
-#define NUM_DT_ENTRIES 1024
-#define NUM_PT_ENTRIES 1024
+#define NUM_TLB_ENTRIES 1024 /* for both DT and PT */
Is it necessary to change this in this patch? In general, it's not a
good idea to mix multiple logical changes together.
Sure, will restore changes in v3.
#define SPAGE_ORDER 12
#define SPAGE_SIZE (1 << SPAGE_ORDER)
@@ -82,7 +79,9 @@
struct rk_iommu_domain {
struct list_head iommus;
+ struct device *dev;
u32 *dt; /* page directory table */
+ dma_addr_t dt_dma;
spinlock_t iommus_lock; /* lock for iommus list */
spinlock_t dt_lock; /* lock for modifying page directory
table */
@@ -98,14 +97,12 @@ struct rk_iommu {
struct iommu_domain *domain; /* domain to which iommu is
attached */
};
-static inline void rk_table_flush(u32 *va, unsigned int count)
+static inline void rk_table_flush(struct device *dev, dma_addr_t dma,
+ unsigned int count)
{
- phys_addr_t pa_start = virt_to_phys(va);
- phys_addr_t pa_end = virt_to_phys(va + count);
- size_t size = pa_end - pa_start;
+ size_t size = count * 4;
It would be a good idea to specify what "count" is. I'm a bit confused
that before it meant bytes and now some multiple of 4?
"count" means PT/DT entry count to flush here. I would add some more
comment on it.
Thank you very much,
Shunqian
Best regards,
Tomasz
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