x86/amd-iommu: Cleanup completion-wait handling

This patch cleans up the implementation of completion-wait
command sending. It also switches the completion indicator
from the MMIO bit to a memory store which can be checked
without IOMMU locking.
As a side effect this patch makes the __iommu_queue_command
function obsolete and so it is removed too.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

1 files changed, 28 insertions, 79 deletions

diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index f8ec28ea3314..073c64b1994b 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -25,6 +25,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/iommu-helper.h>
 #include <linux/iommu.h>
+#include <linux/delay.h>
 #include <asm/proto.h>
 #include <asm/iommu.h>
 #include <asm/gart.h>
@@ -34,7 +35,7 @@
 
 #define CMD_SET_TYPE(cmd, t) ((cmd)->data[1] |= ((t) << 28))
 
-#define EXIT_LOOP_COUNT 10000000
+#define LOOP_TIMEOUT    100000
 
 static DEFINE_RWLOCK(amd_iommu_devtable_lock);
 
@@ -383,10 +384,14 @@ irqreturn_t amd_iommu_int_handler(int irq, void *data)
  *
  ****************************************************************************/
 
-static void build_completion_wait(struct iommu_cmd *cmd)
+static void build_completion_wait(struct iommu_cmd *cmd, u64 address)
 {
+        WARN_ON(address & 0x7ULL);
+
         memset(cmd, 0, sizeof(*cmd));
-        cmd->data[0] = CMD_COMPL_WAIT_INT_MASK;
+        cmd->data[0] = lower_32_bits(__pa(address)) | CMD_COMPL_WAIT_STORE_MASK;
+        cmd->data[1] = upper_32_bits(__pa(address));
+        cmd->data[2] = 1;
         CMD_SET_TYPE(cmd, CMD_COMPL_WAIT);
 }
 
@@ -432,12 +437,14 @@ static void build_inv_iommu_pages(struct iommu_cmd *cmd, u64 address,
  * Writes the command to the IOMMUs command buffer and informs the
  * hardware about the new command. Must be called with iommu->lock held.
  */
-static int __iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
+static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
 {
+        unsigned long flags;
         u32 tail, head;
         u8 *target;
 
         WARN_ON(iommu->cmd_buf_size & CMD_BUFFER_UNINITIALIZED);
+        spin_lock_irqsave(&iommu->lock, flags);
         tail = readl(iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
         target = iommu->cmd_buf + tail;
         memcpy_toio(target, cmd, sizeof(*cmd));
@@ -446,99 +453,41 @@ static int __iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
         if (tail == head)
                 return -ENOMEM;
         writel(tail, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
-
-        return 0;
-}
-
-/*
- * General queuing function for commands. Takes iommu->lock and calls
- * __iommu_queue_command().
- */
-static int iommu_queue_command(struct amd_iommu *iommu, struct iommu_cmd *cmd)
-{
-        unsigned long flags;
-        int ret;
-
-        spin_lock_irqsave(&iommu->lock, flags);
-        ret = __iommu_queue_command(iommu, cmd);
-        if (!ret)
-                iommu->need_sync = true;
+        iommu->need_sync = true;
         spin_unlock_irqrestore(&iommu->lock, flags);
 
-        return ret;
-}
-
-/*
- * This function waits until an IOMMU has completed a completion
- * wait command
- */
-static void __iommu_wait_for_completion(struct amd_iommu *iommu)
-{
-        int ready = 0;
-        unsigned status = 0;
-        unsigned long i = 0;
-
-        INC_STATS_COUNTER(compl_wait);
-
-        while (!ready && (i < EXIT_LOOP_COUNT)) {
-                ++i;
-                /* 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))
-                iommu->reset_in_progress = true;
+        return 0;
 }
 
 /*
  * This function queues a completion wait command into the command
  * buffer of an IOMMU
  */
-static int __iommu_completion_wait(struct amd_iommu *iommu)
-{
-        struct iommu_cmd cmd;
-
-        build_completion_wait(&cmd);
-
-         return __iommu_queue_command(iommu, &cmd);
-}
-
-/*
- * This function is called whenever we need to ensure that the IOMMU has
- * completed execution of all commands we sent. It sends a
- * COMPLETION_WAIT command and waits for it to finish. The IOMMU informs
- * us about that by writing a value to a physical address we pass with
- * the command.
- */
 static int iommu_completion_wait(struct amd_iommu *iommu)
 {
-        int ret = 0;
-        unsigned long flags;
-
-        spin_lock_irqsave(&iommu->lock, flags);
+        struct iommu_cmd cmd;
+        volatile u64 sem = 0;
+        int ret, i = 0;
 
         if (!iommu->need_sync)
-                goto out;
-
-        ret = __iommu_completion_wait(iommu);
+                return 0;
 
-        iommu->need_sync = false;
+        build_completion_wait(&cmd, (u64)&sem);
 
+        ret = iommu_queue_command(iommu, &cmd);
         if (ret)
-                goto out;
-
-        __iommu_wait_for_completion(iommu);
+                return ret;
 
-out:
-        spin_unlock_irqrestore(&iommu->lock, flags);
+        while (sem == 0 && i < LOOP_TIMEOUT) {
+                udelay(1);
+                i += 1;
+        }
 
-        if (iommu->reset_in_progress)
+        if (i == LOOP_TIMEOUT) {
+                pr_alert("AMD-Vi: Completion-Wait loop timed out\n");
+                iommu->reset_in_progress = true;
                 reset_iommu_command_buffer(iommu);
+        }
 
         return 0;
 }