linux-kernel - Re: [PATCH 01/14] Documentation: Add SoundWire summary

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Message-ID: <20171019044443.GE30097@localhost>
Date:   Thu, 19 Oct 2017 10:14:43 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Randy Dunlap <rdunlap@...radead.org>
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>,
        Pierre <pierre-louis.bossart@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Shreyas NC <shreyas.nc@...el.com>, 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: [PATCH 01/14] Documentation: Add SoundWire summary


Thanks for the quick review Randy,

On Wed, Oct 18, 2017 at 08:33:08PM -0700, Randy Dunlap wrote:
> On 10/18/17 20:03, Vinod Koul wrote:

> > +SoundWire is a new interface ratified in 2015 by the MIPI Alliance.
> > +SoundWire is used for transporting data typically related to audio
> > +functions. SoundWire interface is optimized to integrate audio devices in
> > +mobile or mobile inspired systems.
> > +
> > +SoundWire is a 2-Pin multi-drop interface with data and clock line. It
> 
>                   2-pin

ok

> > +The SoundWire protocol supports up to eleven Slave interfaces. All the
> > +interfaces share the common Bus containing data and clock line. Each of the
> > +Slaves can support up to 14 Data Ports. 13 Data Ports are dedicated to audio
> > +transport. Data Port0 is dedicated to transport of Bulk control information,
> > +each of the audio Data Ports (1..14) can support up to 8 Channels in
> 
>                                 (1..13) ??

nope. 1 to 14, both inclusive, thats why 14 Data Ports

> > +Bus:
> > +Implements SoundWire Linux Bus which handles the SoundWire protocol.
> > +It programs all the MIPI defined Slave registers. It represents a SoundWire
> 
>                        MIPI-defined
> 
> > +Master. There can be multiple instances of Bus maybe present in a system.
> 
> eh?
>            Multiple instances of Bus may be present in a system.

sounds better

> > +int sdw_add_bus_master(struct sdw_bus *bus)
> > +{
> > +        if (!bus->dev)
> > +                return -ENODEV;
> > +
> > +        mutex_init(&bus->lock);
> > +        INIT_LIST_HEAD(&bus->slaves);
> > +
> > +	/* Check ACPI for Slave devices */
> > +        sdw_acpi_find_slaves(bus);
> > +
> > +	/* Check DT for Slave devices */
> > +	sdw_of_find_slaves(bus);
> 
> Please use same indentation as sdw_acpi_find_slaves().

ah not sure why it came like this, thanks for pointing out

> > +The MIPI specification requires each Slave interface to expose a unique
> > +48-bit identifier, stored in 6 read only dev_id registers. This dev_id
> 
>                                   read-only

right

> > +identifier, Bus enumerates the Slave device based on the 48-bit identifier.
> > +Slave device and driver match is done based on this 48-bit identifier. Probe
> > +of the Slave driver is called by Bus on successful match between device and
> > +driver id. A parent/child relationship is enforced between Slave and Master
> 
> maybe reverse this order.............                         Master and Slave
> 
> to be in the "parent/child" order?  Unless I have them backwards?

right, will update this

> > +devices (the logical representation is aligned with the physical
> > +connectivity).
> > +
> > +The information on Master/Slave dependencies is stored in platform data,
> > +board-file, ACPI or DT. The MIPI Software specification defines an
> 

ok

-- 
~Vinod