linux-kernel - Re: [RFC PATCH] Soundwire: Initialize multi

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Date:   Mon, 15 Aug 2022 08:37:44 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Khalid Masum <khalid.masum.92@...il.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Vinod Koul <vkoul@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Sanyog Kale <sanyog.r.kale@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Len Brown <lenb@...nel.org>
Subject: Re: [RFC PATCH] Soundwire: Initialize multi_link with fwnode props

On Mon, Aug 15, 2022 at 10:08:07AM +0600, Khalid Masum wrote:
> On 8/14/22 15:45, Greg KH wrote:
> > On Sun, Aug 14, 2022 at 02:04:15PM +0600, Khalid Masum wrote:
> > > According to the TODO, In sw_bus_master_add, bus->multi_link is to be
> > > populated with properties from FW node props. Make this happen by
> > > creating a new fwnode_handle flag FWNODE_FLAG_MULTI_LINKED and use
> > > the flag to store the multi_link value from intel_link_startup. Use
> > > this flag to initialize bus->multi_link.
> > > 
> > > Signed-off-by: Khalid Masum <khalid.masum.92@...il.com>
> > > ---
> > > I do not think adding a new flag for fwnode_handle is a good idea.
> > > So, what would be the best way to initialize bus->multilink with
> > > fwnode props?
> > > 
> > >    -- Khalid Masum
> > > 
> > >   drivers/soundwire/bus.c   | 4 ++--
> > >   drivers/soundwire/intel.c | 1 +
> > >   include/linux/fwnode.h    | 1 +
> > >   3 files changed, 4 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
> > > index a2bfb0434a67..80df1672c60b 100644
> > > --- a/drivers/soundwire/bus.c
> > > +++ b/drivers/soundwire/bus.c
> > > @@ -74,9 +74,9 @@ int sdw_bus_master_add(struct sdw_bus *bus, struct device *parent,
> > >   	/*
> > >   	 * Initialize multi_link flag
> > > -	 * TODO: populate this flag by reading property from FW node
> > >   	 */
> > > -	bus->multi_link = false;
> > > +	bus->multi_link = (fwnode->flags & FWNODE_FLAG_MULTI_LINKED)
> > > +		== FWNODE_FLAG_MULTI_LINKED;

I missed that this was an if statement here, please write this to be
more obvious and readable.

> > >   	if (bus->ops->read_prop) {
> > >   		ret = bus->ops->read_prop(bus);
> > >   		if (ret < 0) {
> > > diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
> > > index 505c5ef061e3..034d1c523ddf 100644
> > > --- a/drivers/soundwire/intel.c
> > > +++ b/drivers/soundwire/intel.c
> > > @@ -1347,6 +1347,7 @@ int intel_link_startup(struct auxiliary_device *auxdev)
> > >   		 */
> > >   		bus->multi_link = true;
> > >   		bus->hw_sync_min_links = 1;
> > > +		dev->fwnode->flags |= FWNODE_FLAG_MULTI_LINKED;
> > >   	}
> > >   	/* Initialize shim, controller */
> > > diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
> > > index 9a81c4410b9f..446a52744953 100644
> > > --- a/include/linux/fwnode.h
> > > +++ b/include/linux/fwnode.h
> > > @@ -32,6 +32,7 @@ struct device;
> > >   #define FWNODE_FLAG_NOT_DEVICE			BIT(1)
> > >   #define FWNODE_FLAG_INITIALIZED			BIT(2)
> > >   #define FWNODE_FLAG_NEEDS_CHILD_BOUND_ON_ADD	BIT(3)
> > > +#define FWNODE_FLAG_MULTI_LINKED		BIT(4)
> > 
> > What does this commit actually change?
> 
> The new flag will lets us save if the device has multilink in fwnode_handle
> whenever needed.
> Then for soundwire/intel, save the multi_link flag into fwnode during
> startup.
> Later at master_add, as written in todo, initialize the multilink flag with
> fwnode's flag property.

And what does that allow to happen?  What changes with all of this?

thanks,

greg k-h