Re: [PATCH] drm: bridge: dw-hdmi: support i2c extended read mode

["Nickey.Yang" <nickey.yang@xxxxxxxxxxxxxx>]

Hi Jose,

在 2017年02月23日 18:17, Jose Abreu 写道:

Hi Nickey,


On 22-02-2017 11:11, Nickey.Yang wrote:

Read EDID func is drm_do_probe_ddc_edid    (in
drivers/gpu/drm/drm_edid.c     Line:1215)
when block = 3  means &msgs[3].addr = DDC_SEGMENT_ADDR(0x30)
,but in dw_hdmi_i2c_xfer
line 299  msgs[i].addr != addr (0x50),  it will printk
"unsupported transfer, changed slave address"
and return -EOPNOTSUPP.

in fact,0x30 not means change slave address but means segment
address.

I am reading the drm_do_probe_ddc_edid and I have one question:
There are 2 writes and one read, but your patch only handles the
write of segment address. What about the start address?

write start address operations
{
1235    .addr = DDC_ADDR,
1236    .flags = 0,
1237   .len = 1,
1238    .buf = &start,
}
will be handle by dw_hdmi_i2c_write. it seems we do need to send start signal actully,
because in dw_hdmi_i2c_write will do length--    and it will skip
while (length--) {

              /*   */
}


In DesignWare HDMI Transmitter Controller Databook,
2.10   E-DID/HDCP/SCDC I 2 C E-DDC Interface

 /* I 2 C Master Interface Normal Mode */
S   slaveaddr[6:0]   W  A  addr[7:0]   datao[7:0]  A/A PA/A

/* I 2 C Master Interface Extended Read Mode */
S  segaddr[6:0]  W X segpointer[7:0] X Sr slaveaddr[6:0] W A addr[7:0]  A datai[7:0]   A P

so we just need add  handles the write of segment address
to  support I2C Master Interface Extended Read Mode.

I am refering to this structure:
1228                 struct i2c_msg msgs[] = {
1229                         {
1230                                 .addr   = DDC_SEGMENT_ADDR,
1231                                 .flags  = 0,
1232                                 .len    = 1,
1233                                 .buf    = &segment,
1234                         }, {
1235                                 .addr   = DDC_ADDR,
1236                                 .flags  = 0,
1237                                 .len    = 1,
1238                                 .buf    = &start,
1239                         }, {
1240                                 .addr   = DDC_ADDR,
1241                                 .flags  = I2C_M_RD,
1242                                 .len    = len,
1243                                 .buf    = buf,
1244                         }

There is a write which indicates DDC segment address and then
there is another write which indicates start address. Shouldn't
this be handled?

Best regards,
Jose Miguel Abreu

Best regards,

Nickey,

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