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Subject[PATCH] drm/bridge: dw-hdmi: fix SCDC configuration for ddc-i2c-bus
Date
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@kwiboo.se>
---
drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 7a47c65d8ecb..fd1c319a4ee0 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -1046,6 +1046,10 @@ static bool dw_hdmi_support_scdc(struct dw_hdmi *hdmi)
if (hdmi->version < 0x200a)
return false;

+ /* Disable if no DDC bus */
+ if (!hdmi->ddc)
+ return false;
+
/* Disable if SCDC is not supported, or if an HF-VSDB block is absent */
if (!display->hdmi.scdc.supported ||
!display->hdmi.scdc.scrambling.supported)
@@ -1683,13 +1687,13 @@ static void hdmi_av_composer(struct dw_hdmi *hdmi,
* Source Devices compliant shall set the
* Source Version = 1.
*/
- drm_scdc_readb(&hdmi->i2c->adap, SCDC_SINK_VERSION,
+ drm_scdc_readb(hdmi->ddc, SCDC_SINK_VERSION,
&bytes);
- drm_scdc_writeb(&hdmi->i2c->adap, SCDC_SOURCE_VERSION,
+ drm_scdc_writeb(hdmi->ddc, SCDC_SOURCE_VERSION,
min_t(u8, bytes, SCDC_MIN_SOURCE_VERSION));

/* Enabled Scrambling in the Sink */
- drm_scdc_set_scrambling(&hdmi->i2c->adap, 1);
+ drm_scdc_set_scrambling(hdmi->ddc, 1);

/*
* To activate the scrambler feature, you must ensure
@@ -1705,7 +1709,7 @@ static void hdmi_av_composer(struct dw_hdmi *hdmi,
hdmi_writeb(hdmi, 0, HDMI_FC_SCRAMBLER_CTRL);
hdmi_writeb(hdmi, (u8)~HDMI_MC_SWRSTZ_TMDSSWRST_REQ,
HDMI_MC_SWRSTZ);
- drm_scdc_set_scrambling(&hdmi->i2c->adap, 0);
+ drm_scdc_set_scrambling(hdmi->ddc, 0);
}
}

--
2.17.1
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