linux-kernel - Re: [PATCH v6 3/5] i3c: dw: Add support for Device NACK Retry configuration

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Message-ID: <aTCfnCikUUuSF3uL@lizhi-Precision-Tower-5810>
Date: Wed, 3 Dec 2025 15:37:48 -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 v6 3/5] i3c: dw: Add support for Device NACK Retry
 configuration

On Wed, Dec 03, 2025 at 03:21:04PM +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.
>
> Add new ops to configure all active DAT entry with dev_nack_retry during
> runtime. Returns error when value exceeds hw specified limit.
>
> Signed-off-by: Adrian Ng Ho Yin <adrianhoyin.ng@...era.com>
> ---

Reviewed-by: Frank Li <Frank.Li@....com>

>  drivers/i3c/master/dw-i3c-master.c | 39 ++++++++++++++++++++++++++++++
>  1 file changed, 39 insertions(+)
>
> diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
> index 9ceedf09c3b6..252559ee2afa 100644
> --- a/drivers/i3c/master/dw-i3c-master.c
> +++ b/drivers/i3c/master/dw-i3c-master.c
> @@ -5,6 +5,7 @@
>   * Author: Vitor Soares <vitor.soares@...opsys.com>
>   */
>
> +#include <linux/bitfield.h>
>  #include <linux/bitops.h>
>  #include <linux/clk.h>
>  #include <linux/completion.h>
> @@ -204,8 +205,12 @@
>  #define EXTENDED_CAPABILITY		0xe8
>  #define SLAVE_CONFIG			0xec
>
> +#define DW_I3C_DEV_NACK_RETRY_CNT_MAX	0x3
> +#define DEV_ADDR_TABLE_DEV_NACK_RETRY_MASK   GENMASK(30, 29)
>  #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) \
> +	FIELD_PREP(DEV_ADDR_TABLE_DEV_NACK_RETRY_MASK, (x))
>  #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))
> @@ -1484,6 +1489,39 @@ static irqreturn_t dw_i3c_master_irq_handler(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>
> +static int dw_i3c_master_set_dev_nack_retry(struct i3c_master_controller *m)
> +{
> +	struct dw_i3c_master *master = to_dw_i3c_master(m);
> +	u32 reg;
> +	int i;
> +
> +	if (m->dev_nack_retry > DW_I3C_DEV_NACK_RETRY_CNT_MAX) {
> +		dev_err(&master->base.dev,
> +			"Value %x exceeds maximum %d\n",
> +			m->dev_nack_retry, DW_I3C_DEV_NACK_RETRY_CNT_MAX);
> +		return -ERANGE;
> +	}
> +
> +	/*
> +	 * 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 &= ~DEV_ADDR_TABLE_DEV_NACK_RETRY_MASK;
> +		reg |= DEV_ADDR_TABLE_DEV_NACK_RETRY_CNT(m->dev_nack_retry);
> +		writel(reg, master->regs +
> +			DEV_ADDR_TABLE_LOC(master->datstartaddr, i));
> +	}
> +
> +	return 0;
> +}
> +
>  static const struct i3c_master_controller_ops dw_mipi_i3c_ops = {
>  	.bus_init = dw_i3c_master_bus_init,
>  	.bus_cleanup = dw_i3c_master_bus_cleanup,
> @@ -1504,6 +1542,7 @@ static const struct i3c_master_controller_ops dw_mipi_i3c_ops = {
>  	.recycle_ibi_slot = dw_i3c_master_recycle_ibi_slot,
>  	.enable_hotjoin = dw_i3c_master_enable_hotjoin,
>  	.disable_hotjoin = dw_i3c_master_disable_hotjoin,
> +	.set_dev_nack_retry = dw_i3c_master_set_dev_nack_retry,
>  };
>
>  /* default platform ops implementations */
> --
> 2.49.GIT
>