Re: [PATCH v2 1/4] drm: Helper for lspcon in drm_dp_dual_mode

["Sharma, Shashank" <shashank.sharma@intel.com>]

Thanks for the review Rodrigo. My comments inline.

Regards
Shashank

On 7/1/2016 3:46 AM, Rodrigo Vivi wrote:
> On Tue, Jun 21, 2016 at 8:00 AM, Shashank Sharma
> <shashank.sharma@intel.com> wrote:
>> This patch adds lspcon support in dp_dual_mode helper.
>> lspcon is essentially a dp->hdmi dongle with dual personality.
>>
>> LS mode: It works as a passive dongle, by level shifting DP++
>> signals to HDMI signals, in LS mode.
>> PCON mode: It works as a protocol converter active dongle
>> in pcon mode, by converting DP++ outputs to HDMI 2.0 outputs.
>>
>> This patch adds support for lspcon detection and mode set
>> switch operations, as a dp dual mode dongle.
>>
>> v2: Addressed review comments from Ville
>> - add adaptor id for lspcon devices (0x08), use it to identify lspcon
>> - change function names
>>    old: drm_lspcon_get_current_mode/drm_lspcon_change_mode
>>    new: drm_lspcon_get_mode/drm_lspcon_set_mode
>> - change drm_lspcon_get_mode type to int, to match
>>    drm_dp_dual_mode_get_tmds_output
>> - change 'err' to 'ret' to match the rest of the functions
>> - remove pointless typecasting during call to dual_mode_read
>> - fix the but while setting value of data, while writing lspcon mode
>> - fix indentation
>> - change mdelay(10) -> msleep(10)
>> - return ETIMEDOUT instead of EFAULT, when lspcon mode change times out
>> - Add an empty line to separate std regs macros and lspcon regs macros
>>    Indent bit definition
>>
>> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
>> ---
>>   drivers/gpu/drm/drm_dp_dual_mode_helper.c | 103 ++++++++++++++++++++++++++++++
>>   include/drm/drm_dp_dual_mode_helper.h     |  25 ++++++++
>>   2 files changed, 128 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
>> index a7b2a75..404e715 100644
>> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
>> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
>> @@ -148,6 +148,14 @@ static bool is_type2_adaptor(uint8_t adaptor_id)
>>                                DP_DUAL_MODE_REV_TYPE2);
>>   }
>>
>> +bool is_lspcon_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN],
>> +       const uint8_t adaptor_id)
>> +{
>> +       return is_hdmi_adaptor(hdmi_id) &&
>> +               (adaptor_id == (DP_DUAL_MODE_REV_TYPE2 |
>
> DP_DUAL_MODE_REV_TYPE2 = 0 so useless here and confusing.
This was a review comment from Ville, on the last patch. I think he 
suggested for the better readability of the code.
>
>> +                       DP_DUAL_MODE_TYPE_TYPE2 | DP_DUAL_MODE_TYPE_LSPCON));
>
> Also this is confusing and took me a while to uderstand that LSPCON is
> the type2 with DPCD
I know, due to LSPCON's dual personality, its complicated to understand. 
I tried to cover some theory, in the cover letter, can add some here too:
LSPCON is a dp->hdmi adapter which can operate in two modes
Passive dongle mode / LS mode: in this mode, it acts as type2 dp dual 
mode adapter (no DPCD readable here)
Active mode / PCON mode: in this mode, it acts as active DP++->HDMI2.0 
protocol convertor dongle, and allows DPCD read/write like a DP++ display.
>
> so my suggestion is to define DP_DUAL_MODE_TYPE_HAS_DPCD (1<<3) with a
> comment this is defined by LSPCON docs since this is not part of VESA
> DP Dual Mode that only defines the Type2 = 0xA0.
>
> so you could use
> TYPE2 | HAS_DPCD = LSPCON.
>
Sure, got it. Will change it like this.
>> +}
>> +
>>   /**
>>    * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
>>    * @adapter: I2C adapter for the DDC bus
>> @@ -203,6 +211,8 @@ enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
>>          ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
>>                                      &adaptor_id, sizeof(adaptor_id));
>>          if (ret == 0) {
>> +               if (is_lspcon_adaptor(hdmi_id, adaptor_id))
>> +                       return DRM_DP_DUAL_MODE_LSPCON;
>>                  if (is_type2_adaptor(adaptor_id)) {
>>                          if (is_hdmi_adaptor(hdmi_id))
>>                                  return DRM_DP_DUAL_MODE_TYPE2_HDMI;
>> @@ -364,3 +374,96 @@ const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
>>          }
>>   }
>>   EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
>> +
>> +/**
>> + * drm_lspcon_get_current_mode: Get LSPCON's current mode of operation by
>> + * by reading offset (0x80, 0x41)
>> + * @i2c_adapter: I2C-over-aux adapter
>> + * @current_mode: out vaiable, current lspcon mode of operation
>> + *
>> + * Returns:
>> + * 0 on success, sets the current_mode value to appropriate mode
>> + * -error on failure
>> + */
>> +int drm_lspcon_get_mode(struct i2c_adapter *adapter,
>> +       enum drm_lspcon_mode *current_mode)
>> +{
>> +       u8 data;
>> +       int ret = 0;
>> +
>> +       if (!current_mode) {
>> +               DRM_ERROR("NULL input\n");
>> +               return -EINVAL;
>> +       }
>> +
>> +       /* Read Status: i2c over aux */
>> +       ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
>> +                       (void *)&data, sizeof(data));
>> +       if (ret < 0) {
>> +               DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
>> +               return -EFAULT;
>> +       }
>
>> +
>> +       if (data & DP_DUAL_MODE_LSPCON_MODE_MASK)
>> +               *current_mode = DRM_LSPCON_MODE_PCON;
>> +       else
>> +               *current_mode = DRM_LSPCON_MODE_LS;
>> +       return 0;
>> +}
>> +EXPORT_SYMBOL(drm_lspcon_get_mode);
>> +
>> +/**
>> + * drm_lspcon_change_mode: Change LSPCON's mode of operation by
>> + * by writing offset (0x80, 0x40)
>> + * @i2c_adapter: I2C-over-aux adapter
>> + * @reqd_mode: required mode of operation
>> + *
>> + * Returns:
>> + * 0 on success, -error on failure/timeout
>> + */
>> +int drm_lspcon_set_mode(struct i2c_adapter *adapter,
>> +       enum drm_lspcon_mode reqd_mode)
>> +{
>> +       u8 data = 0;
>> +       int ret;
>> +       int time_out = 200;
>> +       enum drm_lspcon_mode changed_mode;
>> +
>> +       if (reqd_mode == DRM_LSPCON_MODE_PCON)
>> +               data = DP_DUAL_MODE_LSPCON_MODE_MASK;
>> +
>> +       /* Change mode */
>> +       ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
>> +                       &data, sizeof(data));
>> +       if (ret < 0) {
>> +               DRM_ERROR("LSPCON mode change failed\n");
>> +               return ret;
>> +       }
>> +
>> +       /*
>> +         * Confirm mode change by reading the status bit.
>> +         * Sometimes, it takes a while to change the mode,
>> +         * so wait and retry until time out or done.
>> +         */
>> +       do {
>> +               ret = drm_lspcon_get_mode(adapter, &changed_mode);
>> +               if (ret) {
>> +                       DRM_ERROR("cant confirm LSPCON mode change\n");
>> +                       return ret;
>> +               } else {
>> +                       if (changed_mode != reqd_mode) {
>> +                               msleep(10);
>> +                               time_out -= 10;
>> +                       } else {
>> +                               DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
>> +                                       reqd_mode == DRM_LSPCON_MODE_LS ?
>> +                                               "LS" : "PCON");
>> +                               return 0;
>> +                       }
>> +               }
>> +       } while (time_out);
>> +
>> +       DRM_ERROR("LSPCON mode change timed out\n");
>> +       return -ETIMEDOUT;
>> +}
>> +EXPORT_SYMBOL(drm_lspcon_set_mode);
>> diff --git a/include/drm/drm_dp_dual_mode_helper.h b/include/drm/drm_dp_dual_mode_helper.h
>> index e8a9dfd..441c6cb 100644
>> --- a/include/drm/drm_dp_dual_mode_helper.h
>> +++ b/include/drm/drm_dp_dual_mode_helper.h
>> @@ -24,6 +24,7 @@
>>   #define DRM_DP_DUAL_MODE_HELPER_H
>>
>>   #include <linux/types.h>
>> +#include <drm/drm_edid.h>
>>
>>   /*
>>    * Optional for type 1 DVI adaptors
>> @@ -40,6 +41,7 @@
>>   #define  DP_DUAL_MODE_REV_TYPE2 0x00
>>   #define  DP_DUAL_MODE_TYPE_MASK 0xf0
>>   #define  DP_DUAL_MODE_TYPE_TYPE2 0xa0
>> +#define  DP_DUAL_MODE_TYPE_LSPCON 0x08
>>   #define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/
>>   #define  DP_DUAL_IEEE_OUI_LEN 3
>>   #define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */
>> @@ -55,6 +57,10 @@
>>   #define  DP_DUAL_MODE_CEC_ENABLE 0x01
>>   #define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
>>
>> +#define DP_DUAL_MODE_LSPCON_MODE_CHANGE                0x40
>> +#define DP_DUAL_MODE_LSPCON_CURRENT_MODE               0x41
>
> Where did you get this from? I haven't seen any offset 80, adress 41
> defined anywhere in any of the docs I have here. What am I missing?
>
This offset was added by MCA after Intel requested them to confirm the 
LSPCON modeset success. Initially they gave us just 0x40, which is to 
request a change in mode from LS->PCON or other way. But we saw many 
times this change was not happening, so Intel requested MCA to have 
another register offset (0x41) to confirm the current LSPCON mode.
I dont have an updated MCA doc on this, but I can arrange if you insist 
on this.
>> +#define  DP_DUAL_MODE_LSPCON_MODE_MASK                 0x1
>
> I don't believe "mask" is a good term here....
>
> probably
> DP_DUAL_MODE_LSPCON_MODE_PCON (1<<0)
Agree, will change it to something as you suggested

Shashank
>
>> +
>>   struct i2c_adapter;
>>
>>   ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
>> @@ -63,6 +69,19 @@ ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
>>                                 u8 offset, const void *buffer, size_t size);
>>
>>   /**
>> +* enum drm_lspcon_mode
>> +* @lspcon_mode_ls: Level shifter mode of LSPCON
>> +*      which drives DP++ to HDMI 1.4 conversion.
>> +* @lspcon_mode_pcon: Protocol converter mode of LSPCON
>> +*      which drives DP++ to HDMI 2.0 active conversion.
>> +*/
>> +enum drm_lspcon_mode {
>> +       DRM_LSPCON_MODE_INVALID,
>> +       DRM_LSPCON_MODE_LS,
>> +       DRM_LSPCON_MODE_PCON,
>> +};
>> +
>> +/**
>>    * enum drm_dp_dual_mode_type - Type of the DP dual mode adaptor
>>    * @DRM_DP_DUAL_MODE_NONE: No DP dual mode adaptor
>>    * @DRM_DP_DUAL_MODE_UNKNOWN: Could be either none or type 1 DVI adaptor
>> @@ -70,6 +89,7 @@ ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
>>    * @DRM_DP_DUAL_MODE_TYPE1_HDMI: Type 1 HDMI adaptor
>>    * @DRM_DP_DUAL_MODE_TYPE2_DVI: Type 2 DVI adaptor
>>    * @DRM_DP_DUAL_MODE_TYPE2_HDMI: Type 2 HDMI adaptor
>> + * @DRM_DP_DUAL_MODE_TYPE2_LSPCON: Level shifter /protocol converter
>>    */
>>   enum drm_dp_dual_mode_type {
>>          DRM_DP_DUAL_MODE_NONE,
>> @@ -78,6 +98,7 @@ enum drm_dp_dual_mode_type {
>>          DRM_DP_DUAL_MODE_TYPE1_HDMI,
>>          DRM_DP_DUAL_MODE_TYPE2_DVI,
>>          DRM_DP_DUAL_MODE_TYPE2_HDMI,
>> +       DRM_DP_DUAL_MODE_LSPCON,
>>   };
>>
>>   enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter);
>> @@ -89,4 +110,8 @@ int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
>>                                       struct i2c_adapter *adapter, bool enable);
>>   const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type);
>>
>> +int drm_lspcon_get_mode(struct i2c_adapter *adapter,
>> +       enum drm_lspcon_mode *current_mode);
>> +int drm_lspcon_set_mode(struct i2c_adapter *adapter,
>> +               enum drm_lspcon_mode reqd_mode);
>>   #endif
>> --
>> 1.9.1
>>
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>
>
>
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