Re: [PATCH v7 2/3] i3c: master: Extend address status bit to 4 and add I3C_ADDR_SLOT_EXT_DESIRED

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Frank Li <Frank.li@nxp.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>,
	linux-i3c@lists.infradead.org, linux-kernel@vger.kernel.org,
	arnd@arndb.de, bbrezillon@kernel.org,
	boris.brezillon@collabora.com, conor.culhane@silvaco.com,
	gregkh@linuxfoundation.org, imx@lists.linux.dev,
	pthombar@cadence.com, ravindra.yashvant.shinde@nxp.com
Subject: Re: [PATCH v7 2/3] i3c: master: Extend address status bit to 4 and add I3C_ADDR_SLOT_EXT_DESIRED
Date: Thu, 17 Oct 2024 09:40:59 +0200	[thread overview]
Message-ID: <20241017094059.4e4ed56d@xps-13> (raw)
In-Reply-To: <Zw/lH9pCrkFoXsbH@lizhi-Precision-Tower-5810>

Hi Frank,

Frank.li@nxp.com wrote on Wed, 16 Oct 2024 12:09:03 -0400:

> On Tue, Oct 08, 2024 at 11:18:25AM -0400, Frank Li wrote:
> > Extend the address status bit to 4 and introduce the
> > I3C_ADDR_SLOT_EXT_DESIRED macro to indicate that a device prefers a
> > specific address. This is generally set by the 'assigned-address' in the
> > device tree source (dts) file.
> >
> >  ┌────┬─────────────┬───┬─────────┬───┐
> >  │S/Sr│ 7'h7E RnW=0 │ACK│ ENTDAA  │ T ├────┐
> >  └────┴─────────────┴───┴─────────┴───┘    │
> >  ┌─────────────────────────────────────────┘
> >  │  ┌──┬─────────────┬───┬─────────────────┬────────────────┬───┬─────────┐
> >  └─►│Sr│7'h7E RnW=1  │ACK│48bit UID BCR DCR│Assign 7bit Addr│PAR│ ACK/NACK│
> >     └──┴─────────────┴───┴─────────────────┴────────────────┴───┴─────────┘
> >
> > Some master controllers (such as HCI) need to prepare the entire above
> > transaction before sending it out to the I3C bus. This means that a 7-bit
> > dynamic address needs to be allocated before knowing the target device's
> > UID information.
> >
> > However, some I3C targets may request specific addresses (called as
> > "init_dyn_addr"), which is typically specified by the DT-'s
> > assigned-address property. Lower addresses having higher IBI priority. If
> > it is available, i3c_bus_get_free_addr() preferably return a free address
> > that is not in the list of desired addresses (called as "init_dyn_addr").
> > This allows the device with the "init_dyn_addr" to switch to its
> > "init_dyn_addr" when it hot-joins the I3C bus. Otherwise, if the
> > "init_dyn_addr" is already in use by another I3C device, the target device
> > will not be able to switch to its desired address.
> >
> > If the previous step fails, fallback returning one of the remaining
> > unassigned address, regardless of its state in the desired list.
> >
> > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > ---  
> 
> Miquel:
> 
> 	Do you have a chance to check this patch again?

No worries, it's in my todo list ;)

Thanks,
Miquèl

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