linux-kernel - Re: [PATCH 05/11] drm/bridge: analogix-anx78xx: correct value of TX

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Date:   Mon, 16 Sep 2019 12:36:19 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Andrzej Hajda <a.hajda@...sung.com>,
        Brian Masney <masneyb@...tation.org>,
        bjorn.andersson@...aro.org, robh+dt@...nel.org, agross@...nel.org,
        narmstrong@...libre.com, robdclark@...il.com, sean@...rly.run
Cc:     airlied@...ux.ie, daniel@...ll.ch, mark.rutland@....com,
        Laurent.pinchart@...asonboard.com, jonas@...boo.se,
        jernej.skrabec@...l.net, linus.walleij@...aro.org,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 05/11] drm/bridge: analogix-anx78xx: correct value of
 TX_P0

Hi Andrzej and Brian

On 16/9/19 12:02, Andrzej Hajda wrote:
> On 15.08.2019 02:48, Brian Masney wrote:
>> When attempting to configure this driver on a Nexus 5 phone (msm8974),
>> setting up the dummy i2c bus for TX_P0 would fail due to an -EBUSY
>> error. The downstream MSM kernel sources [1] shows that the proper value
>> for TX_P0 is 0x78, not 0x70, so correct the value to allow device
>> probing to succeed.
>>
>> [1] https://github.com/AICP/kernel_lge_hammerhead/blob/n7.1/drivers/video/slimport/slimport_tx_reg.h
>>
>> Signed-off-by: Brian Masney <masneyb@...tation.org>
>> ---
>>  drivers/gpu/drm/bridge/analogix-anx78xx.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/analogix-anx78xx.h b/drivers/gpu/drm/bridge/analogix-anx78xx.h
>> index 25e063bcecbc..bc511fc605c9 100644
>> --- a/drivers/gpu/drm/bridge/analogix-anx78xx.h
>> +++ b/drivers/gpu/drm/bridge/analogix-anx78xx.h
>> @@ -6,7 +6,7 @@
>>  #ifndef __ANX78xx_H
>>  #define __ANX78xx_H
>>  
>> -#define TX_P0				0x70
>> +#define TX_P0				0x78
> 
> 
> This bothers me little. There are no upstream users, grepping android
> sources suggests that both values can be used [1][2]  (grep for "#define
> TX_P0"), moreover there is code suggesting both values can be valid [3].
> 
> Could you verify datasheet which i2c slave addresses are valid for this
> chip, if both I guess this patch should be reworked.
> 

On my case the valid i2c slave address is 0x70 (from datasheet, very sorry I
can't share it) and the bridge used is an ANX7814, it could be that ANX7808 or
ANX7812 have different slave addresses?

Regards,
 Enric

> 
> [1]:
> https://android.googlesource.com/kernel/msm/+/android-msm-flo-3.4-jb-mr2/drivers/misc/slimport_anx7808/slimport_tx_reg.h
> 
> [2]:
> https://github.com/AndroidGX/SimpleGX-MM-6.0_H815_20d/blob/master/drivers/video/slimport/anx7812/slimport7812_tx_reg.h
> 
> [3]:
> https://github.com/commaai/android_kernel_leeco_msm8996/blob/master/drivers/video/msm/mdss/dp/slimport_custom_declare.h#L73
> 
> 
> Regards
> 
> Andrzej
> 
> 
>>  #define TX_P1				0x7a
>>  #define TX_P2				0x72
>>  
> 
>