linux-kernel - Re: [PATCH v3 03/11] i3c: master: Extend address status bit to 4 and add I3C_ADDR_SLOT_EXT

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Message-ID: <ZsjNA9JV0UKONV32@lizhi-Precision-Tower-5810>
Date: Fri, 23 Aug 2024 13:55:15 -0400
From: Frank Li <Frank.li@....com>
To: Miquel Raynal <miquel.raynal@...tlin.com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Boris Brezillon <boris.brezillon@...labora.com>,
	Parshuram Thombare <pthombar@...ence.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Boris Brezillon <bbrezillon@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Conor Culhane <conor.culhane@...vaco.com>,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
	imx@...ts.linux.dev
Subject: Re: [PATCH v3 03/11] i3c: master: Extend address status bit to 4 and
 add I3C_ADDR_SLOT_EXT_INIT

On Fri, Aug 23, 2024 at 06:04:26PM +0200, Miquel Raynal wrote:
> Hi Frank,
>
>
> >  static bool i3c_bus_dev_addr_is_avail(struct i3c_bus *bus, u8 addr)
> >  {
> >  	enum i3c_addr_slot_status status;
> > @@ -388,6 +405,14 @@ static int i3c_bus_get_free_addr(struct i3c_bus *bus, u8 start_addr)
> >  	enum i3c_addr_slot_status status;
> >  	u8 addr;
> >
> > +	/* try find an address, which have not pre-allocated by assigned-address */
>
> 	Try	to find			has   been
>
> pre-allocated?
>
> > +	for (addr = start_addr; addr < I3C_MAX_ADDR; addr++) {
> > +		status = i3c_bus_get_addr_slot_status_ext(bus, addr);
> > +		if (status == I3C_ADDR_SLOT_FREE)
> > +			return addr;
> > +	}
> > +
> > +	/* use pre-allocoated by assigned-address because such device was removed at bus*/
>
> 	  Use      allocated
>
> pre-allocated or assigned?
>
> I guess the logic should be:
> - try the assigned-address
> - look for a free slot
> - look for an already in use slot that must concern a disconnected
>   device
>
> But the comments are not precise enough IMHO. Can you rephrase them?

How about:

Follow the steps below to obtain the I3C dynamic address:

1. Retrieve the assigned-address from the device tree (DT).
2. Look for an available slot address.
3. Look for an address that is pre-reserved by another device with
assigned-address in DT, but where the device is currently offline.

>
> >  	for (addr = start_addr; addr < I3C_MAX_ADDR; addr++) {
> >  		status = i3c_bus_get_addr_slot_status(bus, addr);
> >  		if (status == I3C_ADDR_SLOT_FREE)
> > @@ -1906,9 +1931,9 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
> >  			goto err_rstdaa;
> >  		}
> >
> > -		i3c_bus_set_addr_slot_status(&master->bus,
> > -					     i3cboardinfo->init_dyn_addr,
> > -					     I3C_ADDR_SLOT_I3C_DEV);
> > +		i3c_bus_set_addr_slot_status_ext(&master->bus,
> > +						 i3cboardinfo->init_dyn_addr,
> > +						 I3C_ADDR_SLOT_I3C_DEV | I3C_ADDR_SLOT_EXT_INIT);
> >
> >  		/*
> >  		 * Only try to create/attach devices that have a static
> > diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
> > index 4601b6957f799..c923b76bbc321 100644
> > --- a/include/linux/i3c/master.h
> > +++ b/include/linux/i3c/master.h
> > @@ -284,6 +284,8 @@ enum i3c_bus_mode {
> >   * @I3C_ADDR_SLOT_I2C_DEV: address is assigned to an I2C device
> >   * @I3C_ADDR_SLOT_I3C_DEV: address is assigned to an I3C device
> >   * @I3C_ADDR_SLOT_STATUS_MASK: address slot mask
> > + * @I3C_ADDR_SLOT_EXT_INIT: the bit mask display of addresses is preferred by some devices,
>
> I'm sorry, but I don't understand what "bit mask display of addresses"
> means.
>
> > + *			    such as the "assigned-address" in device tree source (dts).
> >   *
> >   * On an I3C bus, addresses are assigned dynamically, and we need to know which
> >   * addresses are free to use and which ones are already assigned.
> > @@ -297,9 +299,11 @@ enum i3c_addr_slot_status {
> >  	I3C_ADDR_SLOT_I2C_DEV,
> >  	I3C_ADDR_SLOT_I3C_DEV,
> >  	I3C_ADDR_SLOT_STATUS_MASK = 3,
> > +	I3C_ADDR_SLOT_EXT_STATUS_MASK = 7,
> > +	I3C_ADDR_SLOT_EXT_INIT = BIT(2),
> >  };
> >
> > -#define I3C_ADDR_SLOT_BITS 2
> > +#define I3C_ADDR_SLOT_BITS 4
> >
> >  /**
> >   * struct i3c_bus - I3C bus object
> >
>
>
> Thanks,
> Miquèl