[PATCH] drm/amdgpu: Refine the handshake between guest and server by mailbox

[Christian König]

Am 24.01.2017 um 13:55 schrieb Xue, Ken:
> Add check for bit RCV_MSG_VALID of MAILBOX_CONTROL before reading
> message and after ACK server.
>
> Change-Id: I717a77fd90dfbdfce4dc56e978338ffc5db24fca
> Signed-off-by: Ken Xue <Ken.Xue at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c | 20 ++++++++++++++++++++
>   1 file changed, 20 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c b/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c
> index d2622b6..b2c46db 100644
> --- a/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/mxgpu_vi.c
> @@ -318,10 +318,25 @@ void xgpu_vi_init_golden_registers(struct amdgpu_device *adev)
>   static void xgpu_vi_mailbox_send_ack(struct amdgpu_device *adev)
>   {
>   	u32 reg;
> +	int timeout = VI_MAILBOX_TIMEDOUT;
> +	u32 mask = REG_FIELD_MASK(MAILBOX_CONTROL, RCV_MSG_VALID);
>
>   	reg = RREG32(mmMAILBOX_CONTROL);
>   	reg = REG_SET_FIELD(reg, MAILBOX_CONTROL, RCV_MSG_ACK, 1);
>   	WREG32(mmMAILBOX_CONTROL, reg);
> +
> +	/*Wait for RCV_MSG_VALID to be 0*/
> +	reg = RREG32(mmMAILBOX_CONTROL);
> +	while (reg & mask) {
> +		if (timeout <= 0) {
> +			pr_err("RCV_MSG_VALID is not cleared\n");
> +			break;
> +		}
> +		msleep(1);

Are you sure that you want to use msleep() here instead of mdelay() ?

msleep() is horrible inaccurate, e.g. depending on the definition of HZ 
you can sleep for 10ms instead of 1ms IIRC.

mdelay() is a busy wait, so the CPU can't do anything else useful while 
waiting but I don't think that this will hurt us here.

Regards,
Christian.

> +		timeout -= 1;
> +
> +		reg = RREG32(mmMAILBOX_CONTROL);
> +	}
>   }
>
>   static void xgpu_vi_mailbox_set_valid(struct amdgpu_device *adev, bool val)
> @@ -351,6 +366,11 @@ static int xgpu_vi_mailbox_rcv_msg(struct amdgpu_device *adev,
>   				   enum idh_event event)
>   {
>   	u32 reg;
> +	u32 mask = REG_FIELD_MASK(MAILBOX_CONTROL, RCV_MSG_VALID);
> +
> +	reg = RREG32(mmMAILBOX_CONTROL);
> +	if (!(reg & mask))
> +		return -ENOENT;
>
>   	reg = RREG32(mmMAILBOX_MSGBUF_RCV_DW0);
>   	if (reg != event)
> --
> 2.7.4
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