RE: [PATCH v4 04/11] drm/bridge: it6505: fix aux command write to aux operaction register

[<Hermes.Wu@ite.com.tw>]

>On Thu, Sep 26, 2024 at 03:47:54PM GMT, Hermes Wu wrote:
>> From: Hermes Wu <Hermes.wu@ite.com.tw>
>> 
>> The aux control register command is 4 bits LSB only, adding a MACRO to 
>> get correct operaction command.
>
>Nit: AUX, add (not adding), macro.
>
>What happens if the driver doesn't limit the field? Let me guess, the KSV reading command is 0x10 (it should have been a part of the commit message, BTW), so it overrides some other bits? In such a case this either should be a part of the previous commit, or, at least, come before it.
>

Nothing Happens.

The AUX control command at control register REG_AUX_CMD_REQ is 4 bits LSB only, and b[7:4] is ready only.
AUX FIFO access cannot reach all DPCD area, only KSV FIFO at DPCD(0x6802C).
The commend define use [7:4] to extend original AUX_NATIVE_READ(0) as AUX_NATIVE_READ with AUX FIFO

It should be a part of previous commit.

>> Fixes: b5c84a9edcd4 ("drm/bridge: add it6505 driver")
>> Signed-off-by: Hermes Wu <Hermes.wu@ite.com.tw>
>> ---
>>  drivers/gpu/drm/bridge/ite-it6505.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c 
>> b/drivers/gpu/drm/bridge/ite-it6505.c
>> index 0583abdca75f..d1f5220e04a6 100644
>> --- a/drivers/gpu/drm/bridge/ite-it6505.c
>> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
>> @@ -329,6 +329,8 @@ enum aux_cmd_type {
>>  	CMD_AUX_GET_KSV_LIST = 0x10,
>>  };
>>  
>> +#define GET_AUX_CONTROL_CODE(cmd) ((cmd) & 0x0F)
>> +
>>  enum aux_cmd_reply {
>>  	REPLY_ACK,
>>  	REPLY_NACK,
>> @@ -1000,7 +1002,7 @@ static ssize_t it6505_aux_operation(struct it6505 *it6505,
>>  				  size);
>>  
>>  	/* Aux Fire */
>> -	it6505_write(it6505, REG_AUX_CMD_REQ, cmd);
>> +	it6505_write(it6505, REG_AUX_CMD_REQ, GET_AUX_CONTROL_CODE(cmd));
>>  
>>  	ret = it6505_aux_wait(it6505);
>>  	if (ret < 0)
>> --
>> 2.34.1
>> 
>
>-- 
>With best wishes
>Dmitry
>

BR,
Hermes