Re: [PATCH 1/5] drm: Helper for LSPCON in drm_dp_dual_mode

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

Regards
Shashank

On 5/31/2016 5:40 PM, Ville Syrjälä wrote:
> On Tue, May 31, 2016 at 04:22:08PM +0530, Sharma, Shashank wrote:
>> Thanks for the review, Ville.
>> My comments, inline.
>>
>> Regards
>> Shashank
>> On 5/31/2016 3:22 PM, Ville Syrjälä wrote:
>>> On Tue, May 31, 2016 at 02:55:42PM +0530, Shashank Sharma wrote:
>>>> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
>>>> ---
>>>>    drivers/gpu/drm/drm_dp_dual_mode_helper.c | 85 +++++++++++++++++++++++++++++++
>>>>    include/drm/drm_dp_dual_mode_helper.h     | 29 +++++++++++
>>>>    2 files changed, 114 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..11cab25 100644
>>>> --- a/drivers/gpu/drm/drm_dp_dual_mode_helper.c
>>>> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
>>>> @@ -148,6 +148,12 @@ 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 == 0xa8);
>>>
>>>
>>> I'd probably make this something like
>>>
>>> #define DP_DUAL_MODE_RESERVED_LSPCON 0x08
>>>
>>>           return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
>>> 	                      DP_DUAL_MODE_RESERVED_LSPCON |
>>> 	                      DP_DUAL_MODE_REV_TYPE2);
>>>
>> Thanks, this is a good suggestion, I will do so.
>>>
>>>> +}
>>>> +
>>>>    /**
>>>>     * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
>>>>     * @adapter: I2C adapter for the DDC bus
>>>> @@ -203,6 +209,8 @@ 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 +372,80 @@ 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
>>>> + *
>>>> + * Returns:
>>>> + * Enum representing current mode of operation
>>>> + */
>>>> +enum drm_lspcon_mode
>>>> +drm_lspcon_get_current_mode(struct i2c_adapter *adapter)
>>>
>>> To match with drm_dp_dual_mode_get_tmds_output() this may want to
>>> return the error status, and return the actual mode via a function
>>> argument.
>>>
>> sure, can be done.
>>> As for the name drm_dp_dual_mode_get_lspcon_mode() and
>>> drm_dp_dual_mode_set_lspcon_mode() perhaps?
>>> Or drm_lspcon_get_mode()/drm_lspcon_set_mode() perhaps if we want to
>>> keep things shorter?
>>>
>> Yep, initially I made the same names as you suggested, but
>> drm_dp_dual_mode_get_lspcon_mode dint sound good to me :).
>> drm_lspcon_get/set_mode sounds good.
>>>> +{
>>>> +	u8 data;
>>>> +	int err = 0;
>>>
>>> I used 'ret' in the rest of the code. This is a bit inconsistent.
>> got it.
>>>
>>>> +
>>>> +	/* Read Status: i2c over aux */
>>>> +	err = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_LSPCON_CURRENT_MODE,
>>>> +			(void *)&data, sizeof(data));
>>>
>>> Pointless cast.
>>>
>> good catch, this is unnecessary.
>>>> +	if (err < 0) {
>>>
>>> if (ret) is what I've used elsewhere.
>> got it.
>>>
>>>> +		DRM_ERROR("LSPCON read(0x80, 0x41) failed\n");
>>>
>>> I'm not sure we want and ERROR from a helper. I used DRM_DEBUG_KMS for
>>> the other error paths.
>>>
>> IMHO, This is a failure which needs notice, as it can point out to a HW
>> level problem, or a problem in LSPCON FW, so I will prefer to keep it as
>> error.
>
> Fair enough.
>
>>>> +		return DRM_LSPCON_MODE_INVALID;
>>>> +	}
>>>> +
>>>> +	return data & DP_DUAL_MODE_LSPCON_MODE_MASK ?
>>>> +		DRM_LSPCON_MODE_PCON : DRM_LSPCON_MODE_LS;
>>>> +}
>>>> +EXPORT_SYMBOL(drm_lspcon_get_current_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_change_mode(struct i2c_adapter *adapter,
>>>> +	enum drm_lspcon_mode reqd_mode)
>>>> +{
>>>> +	u8 data;
>>>> +	int err;
>>>> +	int time_out = 200;
>>>> +
>>>> +	if (reqd_mode == DRM_LSPCON_MODE_LS)
>>>> +		data = ~DP_DUAL_MODE_LSPCON_MODE_MASK;
>>>
>>> Is that really correct?
>>>
>> Oops, it was a blunder, but fortunately that register only bothers about
>> bit 0, and that's why it worked, I will fix this.
>>>> +	else
>>>> +		data = DP_DUAL_MODE_LSPCON_MODE_MASK;
>>>> +
>>>> +	/* Change mode */
>>>> +	err = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_LSPCON_MODE_CHANGE,
>>>> +			&data, sizeof(data));
>>>> +	if (err < 0) {
>>>> +		DRM_ERROR("LSPCON mode change failed\n");
>>>> +		return err;
>>>> +	}
>>>> +
>>>> +	/*
>>>> +	* 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.
>>>> +	*/
>>>
>>> indent fail
>> OK.
>>>
>>>> +	while (time_out) {
>>>> +		if (reqd_mode != drm_lspcon_get_current_mode(adapter)) {
>>>> +			mdelay(10);
>>>
>>> mdelay() is bad.
>> Do you think I should replace with some of the non-busy wait (like
>> msleep or so ?)
>
> How long would we typically have to wait for the mode to change?
>
In a normal scenario, it takes max 1-2 iterations (max 20ms) but
on Android trees, We had initially observed it taking as much as 300ms, 
(but thats once in a blue moon). MCA has made some changes in the latest 
LSPCON FW, to make it better. But 200ms is just to be in the safer side.
>>>
>>>> +			time_out -= 10;
>>>> +		} else {
>>>> +			DRM_DEBUG_KMS("LSPCON mode changed to %s\n",
>>>> +			reqd_mode == DRM_LSPCON_MODE_LS ? "LS" : "PCON");
>>>> +			return 0;
>>>> +		}
>>>> +	}
>>>> +
>>>> +	DRM_ERROR("LSPCON mode change timed out\n");
>>>> +	return -EFAULT;
>>>
>>> EFAULT doens't seem like a sensible error value here. ETIMEDOUT I
>>> suppose seems like what we should return.
>> Sure.
>>>
>>>> +}
>>>> +EXPORT_SYMBOL(drm_lspcon_change_mode);
>>>> diff --git a/include/drm/drm_dp_dual_mode_helper.h b/include/drm/drm_dp_dual_mode_helper.h
>>>> index e8a9dfd..f335df5 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
>>>> @@ -54,6 +55,9 @@
>>>>    #define DP_DUAL_MODE_HDMI_PIN_CTRL 0x21
>>>>    #define  DP_DUAL_MODE_CEC_ENABLE 0x01
>>>>    #define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
>>>
>>> Maybe leave an empty line here to separate the standard regs from the
>>> vendor specific ones. Hmm. Actually the vendor register space is
>>> 0x30-0x3f, whereas 0x40+ is reserved. But anyway empty line would
>>> seem warranted.
>>>
>> Got it.
>>>> +#define DP_DUAL_MODE_LSPCON_MODE_CHANGE		0x40
>>>> +#define DP_DUAL_MODE_LSPCON_CURRENT_MODE		0x41
>>>> +#define DP_DUAL_MODE_LSPCON_MODE_MASK			0x1
>>>
>>> Please indent the bit defnition by one space to make it stand out from
>>> the reg defines a little.
>>>
>> Ok, the first two are registers only, I guess this is for
>> DP_DUAL_MODE_LSPCON_MODE_MASK. I will align it.
>>>>    struct i2c_adapter;
>>>>
>>>> @@ -63,6 +67,20 @@ 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_invalid: No idea what's going on
>>>> +* @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,
>>>> +};
>>>
>>> If we change the _get_mode() thing to return the error status separately
>>> from the mode, we won't need the INVALID value.
>>>
>> Agree.
>>>> +
>>>> +/**
>>>>     * 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 +88,7 @@ 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 +97,7 @@ 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 +109,13 @@ 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_dp_dual_mode_ioa_read(struct i2c_adapter *adapter, u8 *buffer,
>>>> +		u8 offset, u8 no_of_bytes);
>>>> +int drm_dp_dual_mode_ioa_write(struct i2c_adapter *adapter, u8 *buffer,
>>>> +		u8 offset, u8 no_of_bytes);
>>>> +int drm_dp_dual_mode_get_edid(void *data,
>>>> +	u8 *buf, unsigned int block, size_t len);
>>>> +enum drm_lspcon_mode drm_lspcon_get_current_mode(struct i2c_adapter *adapter);
>>>> +int drm_lspcon_change_mode(struct i2c_adapter *adapter,
>>>> +		enum drm_lspcon_mode reqd_mode);
>>>>    #endif
>>>> --
>>>> 1.9.1
>>>
>
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