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

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Date:   Mon, 16 Sep 2019 06:40:04 -0400
From:   Brian Masney <masneyb@...tation.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>, bjorn.andersson@...aro.org,
        robh+dt@...nel.org, agross@...nel.org, narmstrong@...libre.com,
        robdclark@...il.com, sean@...rly.run, 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

On Mon, Sep 16, 2019 at 12:36:19PM +0200, Enric Balletbo i Serra wrote:
> 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?

I haven't been able to find any of the datasheets for these devices
online. Product briefs are online (such as 
https://www.analogix.com/en/system/files/ANX7808_product_brief.pdf), but
they don't provide this type of information.

Brian