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

[Vinod Koul]

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...

> >+	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..

-- 
~Vinod