linux-kernel - Re: [PATCH v3 2/3] i3c: dw: Add sysfs support for Device NACK Retry count

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aSSdEW4/WCpGxJ/o@lizhi-Precision-Tower-5810>
Date: Mon, 24 Nov 2025 12:59:45 -0500
From: Frank Li <Frank.li@....com>
To: adrianhoyin.ng@...era.com
Cc: alexandre.belloni@...tlin.com, linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] i3c: dw: Add sysfs support for Device NACK Retry
 count

On Sat, Nov 22, 2025 at 02:00:40AM +0800, adrianhoyin.ng@...era.com wrote:
> From: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
>
> The DesignWare I3C controller supports automatically retrying transactions
> when a device NACKs. This is useful for slave devices that may be
> temporarily busy and not ready to respond immediately.
>
> Adds a controller-wide sysfs attribute, dev_nack_retry_count, to read or
> adjust the retry count at runtime. Returns error when value exceeds hw
> specified limit, and the updated value is programmed into all active DAT
> entries.
>
> Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> ---
>  drivers/i3c/master/dw-i3c-master.c | 69 ++++++++++++++++++++++++++++++
>  drivers/i3c/master/dw-i3c-master.h |  1 +
>  2 files changed, 70 insertions(+)
>
> diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
> index 9ceedf09c3b6..e228c60840af 100644
> --- a/drivers/i3c/master/dw-i3c-master.c
> +++ b/drivers/i3c/master/dw-i3c-master.c
> @@ -204,8 +204,10 @@
>  #define EXTENDED_CAPABILITY		0xe8
>  #define SLAVE_CONFIG			0xec
>
> +#define DW_I3C_DEV_NACK_RETRY_CNT_MAX	0x3
>  #define DEV_ADDR_TABLE_IBI_MDB		BIT(12)
>  #define DEV_ADDR_TABLE_SIR_REJECT	BIT(13)
> +#define DEV_ADDR_TABLE_DEV_NACK_RETRY_CNT(x)	(((x) << 29) & GENMASK(30, 29))
>  #define DEV_ADDR_TABLE_LEGACY_I2C_DEV	BIT(31)
>  #define DEV_ADDR_TABLE_DYNAMIC_ADDR(x)	(((x) << 16) & GENMASK(23, 16))
>  #define DEV_ADDR_TABLE_STATIC_ADDR(x)	((x) & GENMASK(6, 0))
> @@ -295,6 +297,64 @@ to_dw_i3c_master(struct i3c_master_controller *master)
>  	return container_of(master, struct dw_i3c_master, base);
>  }
>
...
> +static ssize_t dw_dev_nack_retry_count_store(struct device *dev,
> +					     struct device_attribute *attr,
> +					     const char *buf, size_t count)
> +{
> +	struct dw_i3c_master *master = dev_get_drvdata(dev);
> +	unsigned long val, flags;
> +	int ret, i;
> +	u32 reg;
> +
> +	ret = kstrtoul(buf, 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val > DW_I3C_DEV_NACK_RETRY_CNT_MAX) {
> +		dev_err(dev,
> +			"Value %lu exceeds maximum %d\n",
> +			val, DW_I3C_DEV_NACK_RETRY_CNT_MAX);
> +		return -ERANGE;
> +	}
> +
> +	master->dev_nack_retry_cnt = val;
> +
> +	spin_lock_irqsave(&master->devs_lock, flags);

I think you'd better to hold i3c_bus_maintenance_lock() lock to make
sure not transfer on going.

Frank
> +	/*
> +	 * Update DAT entries for all currently attached devices.
> +	 * We directly iterate through the master's device array.
> +	 */
> +	for (i = 0; i < master->maxdevs; i++) {
> +		/* Skip free/empty slots */
> +		if (master->free_pos & BIT(i))
> +			continue;
> +
> +		reg = readl(master->regs +
> +				DEV_ADDR_TABLE_LOC(master->datstartaddr, i));
> +		reg &= ~GENMASK(30, 29);
> +		reg |= DEV_ADDR_TABLE_DEV_NACK_RETRY_CNT(val);
> +		writel(reg, master->regs +
> +			DEV_ADDR_TABLE_LOC(master->datstartaddr, i));
> +	}
> +	spin_unlock_irqrestore(&master->devs_lock, flags);
> +
> +	return count;
> +}
> +
...
> --
> 2.49.GIT
>