From mboxrd@z Thu Jan  1 00:00:00 1970
From: Greg KH <greg@kroah.com>
Subject: Re: [PATCH 4.4.y] drm: adv7511: Re-write the i2c address before EDID
 probing
Date: Fri, 8 Sep 2017 09:21:57 +0200
Message-ID: <20170908072157.GB4412@kroah.com>
References: <20170908024602.15692-1-nhan.nguyen.yb@renesas.com>
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To: Nhan Nguyen <nhan.nguyen.yb@renesas.com>
Cc: toru.oishi.zj@renesas.com, binh.nguyen.uw@rvc.renesas.com, David Airlie <airlied@linux.ie>, Archit Taneja <architt@codeaurora.org>, Wolfram Sang <wsa+renesas@sang-engineering.com>, Lars-Peter Clausen <lars@metafoo.de>, Laurent Pinchart <laurent.pinchart@ideasonboard.com>, dri-devel@lists.freedesktop.org, stable@vger.kernel.org, John Stultz <john.stultz@linaro.org>, Thong Ho <thong.ho.px@rvc.renesas.com>
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On Fri, Sep 08, 2017 at 09:46:02AM +0700, Nhan Nguyen wrote:
> commit 3587c856675c45809010c2cee5b21096f6e8e938 upstream.
> 
> I've found that by just turning the chip on and off via the
> POWER_DOWN register, I end up getting i2c_transfer errors on
> HiKey.
> 
> Investigating further, it turns out that some of the register
> state in hardware is getting lost, as the device registers are
> reset when the chip is powered down.
> 
> Thus this patch simply re-writes the i2c address to the
> ADV7511_REG_EDID_I2C_ADDR register to ensure its properly set
> before we try to read the EDID data.
> 
> Cc: David Airlie <airlied@linux.ie>
> Cc: Archit Taneja <architt@codeaurora.org>
> Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: dri-devel@lists.freedesktop.org
> Cc: stable@vger.kernel.org
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Tested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: John Stultz <john.stultz@linaro.org>
> Signed-off-by: Archit Taneja <architt@codeaurora.org>
> Signed-off-by: Thong Ho <thong.ho.px@rvc.renesas.com>
> Signed-off-by: Nhan Nguyen <nhan.nguyen.yb@renesas.com>
> Link: http://patchwork.freedesktop.org/patch/msgid/1484614372-15342-7-git-send-email-john.stultz@linaro.org
> ---
>  drivers/gpu/drm/i2c/adv7511.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)

Can you provide a working backport for the 4.9-stable kernel as well?

Also, please do not send backports for patches that do not also work in
newer stable kernels, like 4.9, I backported some of this series there,
but I shouldn't have to check for you.

thanks,

greg k-h