Radeon regression fix

[Alex Deucher]

On Thu, Sep 29, 2011 at 8:23 PM, Brad Campbell
<lists2009 at fnarfbargle.com> wrote:
> On 29/09/11 23:21, Brad Campbell wrote:
>>
>> On 29/09/11 22:36, Alex Deucher wrote:
>>>
>>> On Thu, Sep 29, 2011 at 10:21 AM, Brad Campbell<brad at fnarfbargle.com>
>>> wrote:
>>>>
>>>> This patch fixes a regression introduced between 2.6.39& 3.1-rc1 whereby
>>>> the displayport AUX channel stopped re-trying commands that elicited
>>>> a DEFER
>>>> response.
>>>>
>>>
>>> It should still be retrying, just restructured slightly. The retry
>>> logic just moved into radeon_dp_i2c_aux_ch(),
>>> radeon_dp_aux_native_write(), and radeon_dp_aux_native_read(), e.g.,
>>>
>>> else if ((ack& AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_DEFER)
>>> udelay(400);
>>>
>>> Perhaps the delay is causing a problem. Does removing the udelay(400);
>>> help?
>
> Looking at it with a nights sleep, it's obvious the code path in
> aux_native_write is ok. Is this a bit cleaner than the last patch?

Looks pretty good.  I was thinking of something more like this (sorry
for the lack of a patch, I'm away from my source trees at the moment):

        while (1) {
                ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
                                            msg, msg_bytes, recv, recv_bytes, 
delay, &ack);

                if (ret < 0)
                        return ret;
                if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
                        return ret;
                else if ((ack & AUX_NATIVE_REPLY_MASK) == 
AUX_NATIVE_REPLY_DEFER)
                        udelay(400);
                else if (ret == 0)
                        return -EPROTO;
                else
                        return -EIO;
        }

Thanks for tracking this down.

Alex

>
> diff --git a/drivers/gpu/drm/radeon/atombios_dp.c
> b/drivers/gpu/drm/radeon/atombios_dp.c
> index 7ad43c6..aacc97d 100644
> --- a/drivers/gpu/drm/radeon/atombios_dp.c
> +++ b/drivers/gpu/drm/radeon/atombios_dp.c
> @@ -158,14 +158,17 @@ static int radeon_dp_aux_native_read(struct
> radeon_connector *radeon_connector,
> ? ? ? ?while (1) {
> ? ? ? ? ? ? ? ?ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?msg, msg_bytes, recv, recv_bytes,
> delay, &ack);
> - ? ? ? ? ? ? ? if (ret == 0)
> + ? ? ? ? ? ? ? if (ret == 0){
> + ? ? ? ? ? ? ? ? ? ? ? if ((ack & AUX_NATIVE_REPLY_MASK) ==
> AUX_NATIVE_REPLY_DEFER){
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? udelay(400);
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? continue;
> + ? ? ? ? ? ? ? ? ? ? ? }
> ? ? ? ? ? ? ? ? ? ? ? ?return -EPROTO;
> + ? ? ? ? ? ? ? }
> ? ? ? ? ? ? ? ?if (ret < 0)
> ? ? ? ? ? ? ? ? ? ? ? ?return ret;
> ? ? ? ? ? ? ? ?if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
> ? ? ? ? ? ? ? ? ? ? ? ?return ret;
> - ? ? ? ? ? ? ? else if ((ack & AUX_NATIVE_REPLY_MASK) ==
> AUX_NATIVE_REPLY_DEFER)
> - ? ? ? ? ? ? ? ? ? ? ? udelay(400);
> ? ? ? ? ? ? ? ?else
> ? ? ? ? ? ? ? ? ? ? ? ?return -EIO;
> ? ? ? ?}
>