linux-kernel - Re: [PATCH v4 3/5] i3c: dw: Add sysfs support for Device NACK Retry count

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Message-ID: <aS3NlA4H/SX8kW2Y@lizhi-Precision-Tower-5810>
Date: Mon, 1 Dec 2025 12:17:08 -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 v4 3/5] i3c: dw: Add sysfs support for Device NACK Retry
 count

On Mon, Dec 01, 2025 at 02:41:56PM +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..a34b4f05dbd3 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_show(struct device *dev,
> +					    struct device_attribute *attr,
> +					    char *buf)
> +{
> +	struct dw_i3c_master *master = dev_get_drvdata(dev);
> +
> +	return sysfs_emit(buf, "%u\n", master->dev_nack_retry_cnt);
> +}
> +
> +static ssize_t dw_dev_nack_retry_count_store(struct device *dev,
> +					     struct device_attribute *attr,
> +					     const char *buf, size_t count)

https://lore.kernel.org/linux-i3c/cover.1763747151.git.adrianhoyin.ng@altera.com/T/#m825490f3f9d7e5332a128d604eed6aee62630ceb

Adrain hunter said MIPI I3C support nack_retry also. So moving it to
master.c should be good idea.

Frank

> +{
> +	struct dw_i3c_master *master = dev_get_drvdata(dev);
> +	unsigned long val;
> +	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;
> +
> +	i3c_bus_maintenance_lock(&master->base.bus);
> +	/*
> +	 * 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));
> +	}
> +	i3c_bus_maintenance_unlock(&master->base.bus);
> +
> +	return count;
> +}
> +
> +static struct device_attribute dev_attr_dev_nack_retry_count =
> +	__ATTR(dev_nack_retry_count, 0644,
> +	       dw_dev_nack_retry_count_show,
> +	       dw_dev_nack_retry_count_store);
> +
>  static void dw_i3c_master_disable(struct dw_i3c_master *master)
>  {
>  	writel(readl(master->regs + DEVICE_CTRL) & ~DEV_CTRL_ENABLE,
> @@ -1598,6 +1658,12 @@ int dw_i3c_common_probe(struct dw_i3c_master *master,
>  	if (ret)
>  		goto err_disable_pm;
>
> +	dev_set_drvdata(&master->base.dev, master);
> +	ret = device_create_file(&master->base.dev, &dev_attr_dev_nack_retry_count);
> +	if (ret)
> +		dev_warn(&master->base.dev,
> +			 "Failed to create dev_nack_retry_count sysfs: %d\n", ret);
> +
>  	return 0;
>
>  err_disable_pm:
> @@ -1617,6 +1683,9 @@ void dw_i3c_common_remove(struct dw_i3c_master *master)
>  	cancel_work_sync(&master->hj_work);
>  	i3c_master_unregister(&master->base);
>
> +	device_remove_file(&master->base.dev, &dev_attr_dev_nack_retry_count);
> +	dev_set_drvdata(&master->base.dev, NULL);
> +
>  	pm_runtime_disable(master->dev);
>  	pm_runtime_set_suspended(master->dev);
>  	pm_runtime_dont_use_autosuspend(master->dev);
> diff --git a/drivers/i3c/master/dw-i3c-master.h b/drivers/i3c/master/dw-i3c-master.h
> index c5cb695c16ab..45fc1774724a 100644
> --- a/drivers/i3c/master/dw-i3c-master.h
> +++ b/drivers/i3c/master/dw-i3c-master.h
> @@ -51,6 +51,7 @@ struct dw_i3c_master {
>  	u32 i2c_fm_timing;
>  	u32 i2c_fmp_timing;
>  	u32 quirks;
> +	u32 dev_nack_retry_cnt;
>  	/*
>  	 * Per-device hardware data, used to manage the device address table
>  	 * (DAT)
> --
> 2.49.GIT
>