Re: AMD/IOMMU: revert "SR56x0 Erratum 64 - Reset all head & tail pointers"

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 03/06/13 08:12, Jan Beulich wrote:
> The code this patch added is redundant with already present code in
> set_iommu_{command_buffer,{event,ppr}_log}_control(). Just switch those
> ones from using writel() to writeq() for consistency.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Yikes - I clearly didn't do a good job looking to see whether this issue
had already been addressed.

Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

>
> --- a/xen/drivers/passthrough/amd/iommu_init.c
> +++ b/xen/drivers/passthrough/amd/iommu_init.c
> @@ -154,11 +154,6 @@ static void register_iommu_cmd_buffer_in
>                           IOMMU_CMD_BUFFER_LENGTH_MASK,
>                           IOMMU_CMD_BUFFER_LENGTH_SHIFT, &entry);
>      writel(entry, iommu->mmio_base+IOMMU_CMD_BUFFER_BASE_HIGH_OFFSET);
> -
> -    /* Reset head/tail pointer. SR56x0 Erratum 64 means this might not happen
> -     * automatically for us. */
> -    writeq(0, iommu->mmio_base + IOMMU_CMD_BUFFER_HEAD_OFFSET);
> -    writeq(0, iommu->mmio_base + IOMMU_CMD_BUFFER_TAIL_OFFSET);
>  }
>  
>  static void register_iommu_event_log_in_mmio_space(struct amd_iommu *iommu)
> @@ -187,11 +182,6 @@ static void register_iommu_event_log_in_
>                          IOMMU_EVENT_LOG_LENGTH_MASK,
>                          IOMMU_EVENT_LOG_LENGTH_SHIFT, &entry);
>      writel(entry, iommu->mmio_base+IOMMU_EVENT_LOG_BASE_HIGH_OFFSET);
> -
> -    /* Reset head/tail pointer. SR56x0 Erratum 64 means this might not happen
> -     * automatically for us. */
> -    writeq(0, iommu->mmio_base + IOMMU_EVENT_LOG_HEAD_OFFSET);
> -    writeq(0, iommu->mmio_base + IOMMU_EVENT_LOG_TAIL_OFFSET);
>  }
>  
>  static void register_iommu_ppr_log_in_mmio_space(struct amd_iommu *iommu)
> @@ -220,9 +210,6 @@ static void register_iommu_ppr_log_in_mm
>                          IOMMU_PPR_LOG_LENGTH_MASK,
>                          IOMMU_PPR_LOG_LENGTH_SHIFT, &entry);
>      writel(entry, iommu->mmio_base + IOMMU_PPR_LOG_BASE_HIGH_OFFSET);
> -
> -    writeq(0, iommu->mmio_base + IOMMU_PPR_LOG_HEAD_OFFSET);
> -    writeq(0, iommu->mmio_base + IOMMU_PPR_LOG_TAIL_OFFSET);
>  }
>  
>  
> @@ -267,8 +254,8 @@ static void set_iommu_command_buffer_con
>      /*reset head and tail pointer manually before enablement */
>      if ( enable )
>      {
> -        writel(0x0, iommu->mmio_base + IOMMU_CMD_BUFFER_HEAD_OFFSET);
> -        writel(0x0, iommu->mmio_base + IOMMU_CMD_BUFFER_TAIL_OFFSET);
> +        writeq(0, iommu->mmio_base + IOMMU_CMD_BUFFER_HEAD_OFFSET);
> +        writeq(0, iommu->mmio_base + IOMMU_CMD_BUFFER_TAIL_OFFSET);
>  
>          iommu_set_bit(&entry, IOMMU_CONTROL_COMMAND_BUFFER_ENABLE_SHIFT);
>      }
> @@ -326,8 +313,8 @@ static void set_iommu_event_log_control(
>      /*reset head and tail pointer manually before enablement */
>      if ( enable )
>      {
> -        writel(0x0, iommu->mmio_base + IOMMU_EVENT_LOG_HEAD_OFFSET);
> -        writel(0x0, iommu->mmio_base + IOMMU_EVENT_LOG_TAIL_OFFSET);
> +        writeq(0, iommu->mmio_base + IOMMU_EVENT_LOG_HEAD_OFFSET);
> +        writeq(0, iommu->mmio_base + IOMMU_EVENT_LOG_TAIL_OFFSET);
>  
>          iommu_set_bit(&entry, IOMMU_CONTROL_EVENT_LOG_INT_SHIFT);
>          iommu_set_bit(&entry, IOMMU_CONTROL_EVENT_LOG_ENABLE_SHIFT);
> @@ -353,8 +340,8 @@ static void set_iommu_ppr_log_control(st
>      /*reset head and tail pointer manually before enablement */
>      if ( enable )
>      {
> -        writel(0x0, iommu->mmio_base + IOMMU_PPR_LOG_HEAD_OFFSET);
> -        writel(0x0, iommu->mmio_base + IOMMU_PPR_LOG_TAIL_OFFSET);
> +        writeq(0, iommu->mmio_base + IOMMU_PPR_LOG_HEAD_OFFSET);
> +        writeq(0, iommu->mmio_base + IOMMU_PPR_LOG_TAIL_OFFSET);
>  
>          iommu_set_bit(&entry, IOMMU_CONTROL_PPR_ENABLE_SHIFT);
>          iommu_set_bit(&entry, IOMMU_CONTROL_PPR_INT_SHIFT);
>
>
>