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Subject[PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait
Date
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
arch/x86/kernel/amd_iommu.c | 17 ++++++++++-------
include/asm-x86/amd_iommu_types.h | 4 ++++
2 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 22d7d05..028e945 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -101,16 +101,13 @@ static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
*/
static int iommu_completion_wait(struct amd_iommu *iommu)
{
- int ret;
+ int ret, ready = 0;
+ unsigned status = 0;
struct iommu_cmd cmd;
- volatile u64 ready = 0;
- unsigned long ready_phys = virt_to_phys(&ready);
unsigned long i = 0;

memset(&cmd, 0, sizeof(cmd));
- cmd.data[0] = LOW_U32(ready_phys) | CMD_COMPL_WAIT_STORE_MASK;
- cmd.data[1] = upper_32_bits(ready_phys);
- cmd.data[2] = 1; /* value written to 'ready' */
+ cmd.data[0] = CMD_COMPL_WAIT_INT_MASK;
CMD_SET_TYPE(&cmd, CMD_COMPL_WAIT);

iommu->need_sync = 0;
@@ -122,9 +119,15 @@ static int iommu_completion_wait(struct amd_iommu *iommu)

while (!ready && (i < EXIT_LOOP_COUNT)) {
++i;
- cpu_relax();
+ /* wait for the bit to become one */
+ status = readl(iommu->mmio_base + MMIO_STATUS_OFFSET);
+ ready = status & MMIO_STATUS_COM_WAIT_INT_MASK;
}

+ /* set bit back to zero */
+ status &= ~MMIO_STATUS_COM_WAIT_INT_MASK;
+ writel(status, iommu->mmio_base + MMIO_STATUS_OFFSET);
+
if (unlikely((i == EXIT_LOOP_COUNT) && printk_ratelimit()))
printk(KERN_WARNING "AMD IOMMU: Completion wait loop failed\n");

diff --git a/include/asm-x86/amd_iommu_types.h b/include/asm-x86/amd_iommu_types.h
index e6b4d5b..2c23834 100644
--- a/include/asm-x86/amd_iommu_types.h
+++ b/include/asm-x86/amd_iommu_types.h
@@ -69,6 +69,9 @@
#define MMIO_EVT_TAIL_OFFSET 0x2018
#define MMIO_STATUS_OFFSET 0x2020

+/* MMIO status bits */
+#define MMIO_STATUS_COM_WAIT_INT_MASK 0x04
+
/* feature control bits */
#define CONTROL_IOMMU_EN 0x00ULL
#define CONTROL_HT_TUN_EN 0x01ULL
@@ -89,6 +92,7 @@
#define CMD_INV_IOMMU_PAGES 0x03

#define CMD_COMPL_WAIT_STORE_MASK 0x01
+#define CMD_COMPL_WAIT_INT_MASK 0x02
#define CMD_INV_IOMMU_PAGES_SIZE_MASK 0x01
#define CMD_INV_IOMMU_PAGES_PDE_MASK 0x02

--
1.5.3.7



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