linux-kernel - Re: [PATCH 0/4] i3c: dw: Add support for Device NACK Retry count

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Message-ID: <20251106221048367d654a@mail.local>
Date: Thu, 6 Nov 2025 23:10:48 +0100
From: Alexandre Belloni <alexandre.belloni@...tlin.com>
To: adrianhoyin.ng@...era.com
Cc: Frank.Li@....com, wsa+renesas@...g-engineering.com, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, dinguyen@...nel.org,
	linux-i3c@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] i3c: dw: Add support for Device NACK Retry count

On 04/11/2025 16:51:07+0800, adrianhoyin.ng@...era.com wrote:
> From: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> 
> This series adds support for configuring the Device NACK Retry count
> in the Synopsys DesignWare I3C master controller and enables the
> corresponding property in the Altera Agilex5 device tree.
> 
> Some I3C slave devices may temporarily NACK transactions when they are
> busy or not ready to respond. To enhance bus reliability, the DesignWare
> I3C controller supports a programmable retry mechanism that automatically
> reissues NACKed transactions. This series introduces the
> snps,dev-nack-retry-cnt device tree property to configure this retry
> count. The value is written into the Device Address Table (DAT) entry for
> each I3C device, enabling fine-grained control of retry behavior.
> 

As Frank explained, this needs to be a per device sysfs file because
this is definitively policy and not HW related. This file should only be
visible when the bus supports retrying.

Don't forget to add documentation in ABI/testing/sysfs-bus-i3c

> This series also fixes an issue where existing DAT entries could be
> overwritten when the driver restores device addresses. Update
> dw_i3c_master_restore_addrs to preserve existing bits in each
> DAT entry when restoring addresses.
> 
> Adrian Ng Ho Yin (4):
>   dt-bindings: i3c: Add snps,dev-nack-retry-cnt property to Synopsys I3C
>     master
>   arm64: dts: intel: agilex5: Add snps,dev-nack-retry-cnt property for
>     I3C controllers
>   i3c: dw: Add support for Device NACK Retry count
>   i3c: dw: Preserve DAT entry bits when restoring addresses
> 
>  .../bindings/i3c/snps,dw-i3c-master.yaml      |  8 ++++
>  .../arm64/boot/dts/intel/socfpga_agilex5.dtsi |  2 +
>  drivers/i3c/master/dw-i3c-master.c            | 40 ++++++++++++++++++-
>  drivers/i3c/master/dw-i3c-master.h            |  1 +
>  4 files changed, 49 insertions(+), 2 deletions(-)
> 
> -- 
> 2.49.GIT
> 

-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com