linux-kernel - Re: [PATCH] drm/bridge: dw-hdmi: fix SCDC configuration for ddc-i2c-bus

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Date:   Thu, 25 Apr 2019 10:42:05 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Jonas Karlman <jonas@...boo.se>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Cc:     Archit Taneja <architt@...eaurora.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Neil Armstrong <narmstrong@...libre.com>,
        Sean Paul <seanpaul@...omium.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Heiko Stuebner <heiko@...ech.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/bridge: dw-hdmi: fix SCDC configuration for
 ddc-i2c-bus

On 21.04.2019 10:25, Jonas Karlman wrote:
> When ddc-i2c-bus property is used, a NULL pointer dereference is reported:
>
> [   31.041669] Unable to handle kernel NULL pointer dereference at virtual address 00000008
> [   31.041671] pgd = 4d3c16f6
> [   31.041673] [00000008] *pgd=00000000
> [   31.041678] Internal error: Oops: 5 [#1] SMP ARM
>
> [   31.041711] Hardware name: Rockchip (Device Tree)
> [   31.041718] PC is at i2c_transfer+0x8/0xe4
> [   31.041721] LR is at drm_scdc_read+0x54/0x84
> [   31.041723] pc : [<c073273c>]    lr : [<c05926c4>]    psr: 280f0013
> [   31.041725] sp : edffdad0  ip : 5ccb5511  fp : 00000058
> [   31.041727] r10: 00000780  r9 : edf91608  r8 : c11b0f48
> [   31.041728] r7 : 00000438  r6 : 00000000  r5 : 00000000  r4 : 00000000
> [   31.041730] r3 : edffdae7  r2 : 00000002  r1 : edffdaec  r0 : 00000000
>
> [   31.041908] [<c073273c>] (i2c_transfer) from [<c05926c4>] (drm_scdc_read+0x54/0x84)
> [   31.041913] [<c05926c4>] (drm_scdc_read) from [<c0592858>] (drm_scdc_set_scrambling+0x30/0xbc)
> [   31.041919] [<c0592858>] (drm_scdc_set_scrambling) from [<c05cc0f4>] (dw_hdmi_update_power+0x1440/0x1610)
> [   31.041926] [<c05cc0f4>] (dw_hdmi_update_power) from [<c05cc574>] (dw_hdmi_bridge_enable+0x2c/0x70)
> [   31.041932] [<c05cc574>] (dw_hdmi_bridge_enable) from [<c05aed48>] (drm_bridge_enable+0x24/0x34)
> [   31.041938] [<c05aed48>] (drm_bridge_enable) from [<c0591060>] (drm_atomic_helper_commit_modeset_enables+0x114/0x220)
> [   31.041943] [<c0591060>] (drm_atomic_helper_commit_modeset_enables) from [<c05c3fe0>] (rockchip_atomic_helper_commit_tail_rpm+0x28/0x64)
>
> hdmi->i2c may not be set when ddc-i2c-bus property is used in device tree.
> Fix this by using hdmi->ddc as the i2c adapter when calling drm_scdc_*().
> Also report that SCDC is not supported when there is no DDC bus.
>
> Fixes: 264fce6cc2c1 ("drm/bridge: dw-hdmi: Add SCDC and TMDS Scrambling support")
> Signed-off-by: Jonas Karlman <jonas@...boo.se>


Pushed to drm-misc-fixes.

Regards

Andrzej