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: Mon, 21 Oct 2024 12:02:54 +0200	[thread overview]
Message-ID: <20241021120254.76831170@xps-13> (raw)
In-Reply-To: <20241008-i3c_dts_assign-v7-2-96ec93d1f34c@nxp.com>

Hi Frank,

Frank.Li@nxp.com wrote on Tue, 08 Oct 2024 11:18:25 -0400:

> 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>

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>

Thanks,
Miquèl

-- 
linux-i3c mailing list
linux-i3c@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-i3c