Subject: Re: [PATCH v11 17/19] drm: bridge: analogix/dp: expand the look time
 for waiting AUX CH reply
To: Jingoo Han <jingoohan1@gmail.com>, "'Inki Dae'" <inki.dae@samsung.com>,
        "'Mark Yao'" <mark.yao@rock-chips.com>,
        "'Heiko Stuebner'" <heiko@sntech.de>
References: <1450236018-1118-1-git-send-email-ykk@rock-chips.com>
 <1450238257-3274-1-git-send-email-ykk@rock-chips.com>
 <000a01d13cb4$0f81f510$2e85df30$@com>
Cc: "'Thierry Reding'" <treding@nvidia.com>,
        "'Krzysztof Kozlowski'" <k.kozlowski@samsung.com>,
        "'Rob Herring'" <robh+dt@kernel.org>,
        "'Russell King'" <linux@arm.linux.org.uk>, emil.l.velikov@gmail.com,
        "'Gustavo Padovan'" <gustavo.padovan@collabora.co.uk>,
        "'Kishon Vijay Abraham I'" <kishon@ti.com>, javier@osg.samsung.com,
        "'Andy Yan'" <andy.yan@rock-chips.com>,
        dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
        linux-rockchip@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org
From: Yakir Yang <ykk@rock-chips.com>
Message-ID: <567A21EC.4010003@rock-chips.com>
Date: Wed, 23 Dec 2015 12:24:12 +0800
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Hi Jingoo,

On 12/22/2015 08:26 PM, Jingoo Han wrote:
> On Wednesday, December 16, 2015 12:58 PM, Yakir Yang wrote:
>> After test on rockchiop platform, i found sometims driver would failed
>> at reading EDID message. After debugging more, i found that it's okay
>> to read_a byte from i2c, but it would failed at AUX transcation if we
>> try to ready multi-bytes from i2c.
>>
>> Driver just can't received the AUX CH reply command, even no AUX error
>> code. I may guess that the AUX wait time is not enough, so I try to
>> expand the AUX wait time, and i do see this could fix the EDID read
>> failed at rockchip platform.
>>
>> And I thought that expand the wait time won't hurt Exynos platform too
>> much, cause Exynos didn't have this problem, then driver would received
>> the reply command very soon, so no more additional wait time would bring
>> to Exynos platform.
>>
>> Signed-off-by: Yakir Yang <ykk@rock-chips.com>
>> ---
>> Changes in v11: None
>> Changes in v10: None
>> Changes in v9: None
>> Changes in v8: None
>> Changes in v7: None
>> Changes in v6: None
>> Changes in v5: None
>> Changes in v4: None
>> Changes in v3: None
>> Changes in v2: None
>>
>>   drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
>> b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
>> index c7e2959..dc376bd 100644
>> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
>> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_reg.c
>> @@ -482,7 +482,7 @@ int analogix_dp_start_aux_transaction(struct analogix_dp_device *dp)
>>   	reg = readl(dp->reg_base + ANALOGIX_DP_INT_STA);
>>   	while (!(reg & RPLY_RECEIV)) {
>>   		timeout_loop++;
>> -		if (DP_TIMEOUT_LOOP_COUNT < timeout_loop) {
>> +		if (DP_TIMEOUT_LOOP_COUNT * 10 < timeout_loop) {
> No, I hate this coding.
> analogix_dp_reg.c is the common code that can be shared by various SoCs.
> Please, find another way.

Okay, I have double checked that i do have this problem in my side. 
Hmmm.....
I thought it's okay for you if I expand the "DP_TIMEOUT_LOOP_COUNT" 
directly,
it won't hurt Exynos platform too much, cause Exynos didn't have this 
problem,
then driver would received,the reply command very soon, so no more 
additional
wait time would bring to Exynos platform.

And actually the datasheet haven't described the spec of aux reply delay 
time.

Thanks,
- Yakir

> Best regards,
> Jingoo Han
>
>
>>   			dev_err(dp->dev, "AUX CH command reply failed!\n");
>>   			return -ETIMEDOUT;
>>   		}
>> --
>> 1.9.1
>
>
>
>


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