linux-kernel - Re: [PATCH v2] i3c: master: svc: adjust the first broadcast speed

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Message-ID: <Zpp/uv0yeEhld6We@lizhi-Precision-Tower-5810>
Date: Fri, 19 Jul 2024 11:01:14 -0400
From: Frank Li <Frank.li@....com>
To: carlos.song@....com
Cc: miquel.raynal@...tlin.com, conor.culhane@...vaco.com,
	alexandre.belloni@...tlin.com, linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
	linux-imx@....com
Subject: Re: [PATCH v2] i3c: master: svc: adjust the first broadcast speed

On Fri, Jul 19, 2024 at 04:03:51PM +0800, carlos.song@....com wrote:
> From: Carlos Song <carlos.song@....com>
> 
> According to the i3c spec 6.2 Timing Specification, the first
> broadcast open drain timing should be adjust to High Period
> of SCL Clock is 200ns at least. I3C device working as a i2c
> device will see the broadcast to close its Spike Filter to
> change to i3c mode. After that I3C open drain SCL high level
> should be adjust to 32ns~45ns.
> 
> Signed-off-by: Carlos Song <carlos.song@....com>
> ---
> Change for V2:
> - use slow_speed instead of first_broadcast
> - add default_speed variable in svc_i3c_xfer to avoid set default
>   speed every time
> - change start_xfer if else for easy understand
> ---
>  drivers/i3c/master/svc-i3c-master.c | 55 +++++++++++++++++++++++++++++
>  1 file changed, 55 insertions(+)
> 
> diff --git a/drivers/i3c/master/svc-i3c-master.c b/drivers/i3c/master/svc-i3c-master.c
> index 78116530f431..7cd3a9a4d7dd 100644
> --- a/drivers/i3c/master/svc-i3c-master.c
> +++ b/drivers/i3c/master/svc-i3c-master.c
> @@ -142,6 +142,7 @@ struct svc_i3c_cmd {
>  	unsigned int actual_len;
>  	struct i3c_priv_xfer *xfer;
>  	bool continued;
> +	bool slow_address;
>  };
>  
>  struct svc_i3c_xfer {
> @@ -214,6 +215,11 @@ struct svc_i3c_master {
>  	} ibi;
>  	struct mutex lock;
>  	int enabled_events;
> +
> +	unsigned long fclk_rate;
> +	u32 mctrl_config;
> +	bool slow_speed;
> +	bool default_speed;

I think you needn't two varible 'slow_speed' and 'default_speed'.
	default_speed should always !slow_speed

Frank

>  };
>  
>  /**
> @@ -531,6 +537,43 @@ static irqreturn_t svc_i3c_master_irq_handler(int irq, void *dev_id)
>  	return IRQ_HANDLED;
>  }
>  
> +static void svc_i3c_master_set_slow_address_speed(struct svc_i3c_master *master)
> +{
> +	struct i3c_bus *bus = i3c_master_get_bus(&master->base);
> +	u32 ppbaud, odbaud, odhpp, mconfig;
> +
> +	master->mctrl_config = readl(master->regs + SVC_I3C_MCONFIG);
> +	mconfig = master->mctrl_config;
> +
> +	/*
> +	 * Set the I3C OPEN-DRAIN mode to the FM speed of 50% duty-cycle(400K/2500ns),
> +	 * so that the first broadcast is visible to all devices on the i3c bus.
> +	 * I3C device with 50ns filter will turn off the filter.
> +	 */
> +
> +	ppbaud = FIELD_GET(GENMASK(11, 8), mconfig);
> +	odhpp = 0;
> +	odbaud = DIV_ROUND_UP(master->fclk_rate, bus->scl_rate.i2c * (2 + 2 * ppbaud)) - 1;
> +	mconfig &= ~GENMASK(24, 16);
> +	mconfig |= SVC_I3C_MCONFIG_ODBAUD(odbaud) | SVC_I3C_MCONFIG_ODHPP(odhpp);
> +
> +	writel(mconfig, master->regs + SVC_I3C_MCONFIG);
> +	master->slow_speed = false;
> +}
> +
> +static void svc_i3c_master_set_default_speed(struct svc_i3c_master *master)
> +{
> +	/*
> +	 * The bus mode is already determined when the bus is initialized, so setting initial
> +	 * configuration back to the controller. No need to set it in every transfer, just
> +	 * restore it once time.
> +	 */
> +	if (!master->default_speed) {
> +		writel(master->mctrl_config, master->regs + SVC_I3C_MCONFIG);
> +		master->default_speed = true;
> +	}
> +}
> +
>  static int svc_i3c_master_bus_init(struct i3c_master_controller *m)
>  {
>  	struct svc_i3c_master *master = to_svc_i3c_master(m);
> @@ -624,6 +667,8 @@ static int svc_i3c_master_bus_init(struct i3c_master_controller *m)
>  	      SVC_I3C_MCONFIG_I2CBAUD(i2cbaud);
>  	writel(reg, master->regs + SVC_I3C_MCONFIG);
>  
> +	master->slow_speed = true;
> +	master->fclk_rate = fclk_rate;
>  	/* Master core's registration */
>  	ret = i3c_master_get_free_addr(m, 0);
>  	if (ret < 0)
> @@ -1251,6 +1296,11 @@ static void svc_i3c_master_start_xfer_locked(struct svc_i3c_master *master)
>  	for (i = 0; i < xfer->ncmds; i++) {
>  		struct svc_i3c_cmd *cmd = &xfer->cmds[i];
>  
> +		if (cmd->slow_address)
> +			svc_i3c_master_set_slow_address_speed(master);
> +		else
> +			svc_i3c_master_set_default_speed(master);
> +
>  		ret = svc_i3c_master_xfer(master, cmd->rnw, xfer->type,
>  					  cmd->addr, cmd->in, cmd->out,
>  					  cmd->len, &cmd->actual_len,
> @@ -1346,6 +1396,11 @@ static int svc_i3c_master_send_bdcast_ccc_cmd(struct svc_i3c_master *master,
>  	cmd->actual_len = 0;
>  	cmd->continued = false;
>  
> +	if (master->slow_speed)
> +		cmd->slow_address = true;
> +	else
> +		cmd->slow_address = false;
> +
>  	mutex_lock(&master->lock);
>  	svc_i3c_master_enqueue_xfer(master, xfer);
>  	if (!wait_for_completion_timeout(&xfer->comp, msecs_to_jiffies(1000)))
> -- 
> 2.34.1
>