linux-kernel - Re: Radeon regression fix

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Date:	Thu, 29 Sep 2011 23:21:02 +0800
From:	Brad Campbell <brad@...rfbargle.com>
To:	Alex Deucher <alexdeucher@...il.com>
CC:	airlied@...hat.com, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: Radeon regression fix

On 29/09/11 22:36, Alex Deucher wrote:
> On Thu, Sep 29, 2011 at 10:21 AM, Brad Campbell<brad@...rfbargle.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?

How's this look ?


diff --git a/drivers/gpu/drm/radeon/atombios_dp.c 
b/drivers/gpu/drm/radeon/atombios_dp.c
index 7ad43c6..aa5624a 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -128,12 +128,14 @@ static int radeon_dp_aux_native_write(struct 
radeon_connector *radeon_connector,
         while (1) {
                 ret = radeon_process_aux_ch(dig_connector->dp_i2c_bus,
                                             msg, msg_bytes, NULL, 0, 
delay, &ack);
+               if (ret == 0 && ((ack & AUX_NATIVE_REPLY_MASK) == 
AUX_NATIVE_REPLY_DEFER)){
+                       udelay(400);
+                       continue;
+               }
                 if (ret < 0)
                         return ret;
                 if ((ack & AUX_NATIVE_REPLY_MASK) == AUX_NATIVE_REPLY_ACK)
                         break;
-               else if ((ack & AUX_NATIVE_REPLY_MASK) == 
AUX_NATIVE_REPLY_DEFER)
-                       udelay(400);
                 else
                         return -EIO;
         }
@@ -158,14 +160,16 @@ 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 && ((ack & AUX_NATIVE_REPLY_MASK) == 
AUX_NATIVE_REPLY_DEFER)){
+                       udelay(400);
+                       continue;
+               }
                 if (ret == 0)
                         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;
         }
--
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