linux-kernel - Re: [alsa-devel] [PATCH v4 04/15] soundwire: Add MIPI DisCo property helpers

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Message-ID: <557584aa-a82b-f495-4e37-cec250178d50@linux.intel.com>
Date:   Sun, 3 Dec 2017 20:50:07 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Vinod Koul <vinod.koul@...el.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        ALSA <alsa-devel@...a-project.org>, Mark <broonie@...nel.org>,
        Takashi <tiwai@...e.de>, patches.audio@...el.com,
        alan@...ux.intel.com,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        Sagar Dharia <sdharia@...eaurora.org>,
        srinivas.kandagatla@...aro.org, plai@...eaurora.org,
        Sudheer Papothi <spapothi@...eaurora.org>
Subject: Re: [alsa-devel] [PATCH v4 04/15] soundwire: Add MIPI DisCo property
 helpers

On 12/3/17 10:52 AM, Vinod Koul wrote:
> On Fri, Dec 01, 2017 at 04:49:01PM -0600, Pierre-Louis Bossart wrote:
> 
>>> +int sdw_master_read_prop(struct sdw_bus *bus)
>>> +{
>>> +	struct sdw_master_prop *prop = &bus->prop;
>>> +	struct fwnode_handle *link;
>>> +	unsigned int count = 0;
>>> +	char name[32];
>>> +	int nval, i;
>>> +
>>> +	device_property_read_u32(bus->dev,
>>> +			"mipi-sdw-sw-interface-revision", &prop->revision);
>>> +	device_property_read_u32(bus->dev, "mipi-sdw-master-count", &count);
>>> +
>>> +	/* Find link handle */
>>> +	snprintf(name, sizeof(name),
>>> +			"mipi-sdw-link-%d-subproperties", bus->link_id);
>>
>> if you follow the DisCo spec, this property is at the controller level,
>> isn't there a confusion between controller/master here, and consequently are
>> we reading the same things multiple times or using the wrong bus parameter?
> 
> Not sure I follow, this one is for a specific master ie a specfic link.
> we need to read respective master thru mipi-sdw-link-N-subproperties
> 
>> If I look at intel_probe(), there is a clear reference to a link_id, and
>> then you set the pointer to this read_prop which reads the number of links,
>> which looks like the wrong order. You can't assign a link ID before knowing
>> how many links there are - or you may be unable to detect issues.
> 
> Sorry I dont follow this part. FWIW, when master driver is enumerated it
> know the link_id value and then sets the read_prop and then these are read.
> 
> Here we are reading "a specific link property" with the knowledge of link_id
> value...

the sdw_master-count is at the controller level, and the linkid has to 
be < master_count.

The fact that you are reading this property for each master instance is 
the problem.

> 
>>> +	fwnode_property_read_u32(link, "mipi-sdw-default-frame-rate",
>>> +				&prop->default_frame_rate);
>>> +	fwnode_property_read_u32(link, "mipi-sdw-default-frame-row-size",
>>> +				&prop->default_row);
>>> +	fwnode_property_read_u32(link, "mipi-sdw-default-frame-col-size",
>>
>> This is fine, just wondering if we should warnings if the values make no
>> sense, e.g. the DisCo spec states in Note1 page 15 that the values are
>> interrelated.
> 
> I think we discussed in past and that would kind of form the firmware
> validation. We check all the values to see if firmware gave us sane values..
> 
>>> +	/*
>>> +	 * Based on each DPn port, get source and sink dpn properties.
>>> +	 * Also, some ports can operate as both source or sink.
>>> +	 */
>>> +
>>> +	/* Allocate memory for set bits in port lists */
>>> +	nval = hweight32(prop->source_ports);
>>> +	num_of_ports += nval;
>>
>> this and...
>>
>>> +	prop->src_dpn_prop = devm_kcalloc(&slave->dev, nval,
>>> +				sizeof(*prop->src_dpn_prop), GFP_KERNEL);
>>> +	if (!prop->src_dpn_prop)
>>> +		return -ENOMEM;
>>> +
>>> +	/* Read dpn properties for source port(s) */
>>> +	sdw_slave_read_dpn(slave, prop->src_dpn_prop, nval,
>>> +			prop->source_ports, "source");
>>> +
>>> +	nval = hweight32(prop->sink_ports);
>>> +	num_of_ports += nval;
>>
>> ... this is no longer needed since...
>>
>>> +	prop->sink_dpn_prop = devm_kcalloc(&slave->dev, nval,
>>> +				sizeof(*prop->sink_dpn_prop), GFP_KERNEL);
>>> +	if (!prop->sink_dpn_prop)
>>> +		return -ENOMEM;
>>> +
>>> +	/* Read dpn properties for sink port(s) */
>>> +	sdw_slave_read_dpn(slave, prop->sink_dpn_prop, nval,
>>> +			prop->sink_ports, "sink");
>>> +
>>> +	/* some ports are bidirectional so check total ports by ORing */
>>> +	nval = prop->source_ports | prop->sink_ports;
>>> +	num_of_ports = hweight32(nval) + 1; /* add 1 for DP0 */
>>
>> ... you reassign the value here. That was one earlier feedback from me but
>> you left the variable incrementation in the code.
> 
> This seems to have artifact of merge conflicts as I clearly remember removing
> this, thanks for pointing will remove these..
> 
>>> +/**
>>> + * enum sdw_clk_stop_mode - Clock Stop modes
>>> + * @SDW_CLK_STOP_MODE0: Slave can continue operation seamlessly on clock
>>> + * restart
>>> + * @SDW_CLK_STOP_MODE1: Slave may have entered a deeper power-saving mode,
>>> + * not capable of continuing operation seamlessly when the clock restarts
>>> + */
>>> +enum sdw_clk_stop_mode {
>>> +	SDW_CLK_STOP_MODE0 = 1,
>>> +	SDW_CLK_STOP_MODE1 = 2,
>>
>> why not 0 and 1?
> 
> why not 1 and 2 :D
> 
> I think it was to ensure we have a non zero value, but am not sure, will
> check though..

I don't think the value matter and you should use the same conventions 
for such enums.

>