linux-kernel - Re: [PATCH v6 3/5] i3c: master: svc: Add basic HDR mode support

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Message-ID: <aPnngQdwEqHgPc7R@smile.fi.intel.com>
Date: Thu, 23 Oct 2025 11:29:53 +0300
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Frank Li <Frank.Li@....com>
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-i3c@...ts.infradead.org,
	linux-kernel@...r.kernel.org, imx@...ts.linux.dev,
	linux-iio@...r.kernel.org, joshua.yeong@...rfivetech.com,
	devicetree@...r.kernel.org, Carlos Song <carlos.song@....com>
Subject: Re: [PATCH v6 3/5] i3c: master: svc: Add basic HDR mode support

On Tue, Oct 14, 2025 at 12:40:02PM -0400, Frank Li wrote:
> Add basic HDR mode support for the svs I3C master driver.
> 
> Only support for private transfers and does not support sending CCC
> commands in HDR mode.
> 
> Key differences:
> - HDR uses commands (0x00-0x7F for write, 0x80-0xFF for read) to
> distinguish transfer direction.
> - HDR read/write commands must be written to FIFO before issuing the I3C
> address command. The hardware automatically sends the standard CCC command
> to enter HDR mode.
> - HDR exit pattern must be sent instead of send a stop after transfer
> completion.
> - Read/write data size must be an even number.

...

> +static void svc_i3c_master_emit_force_exit(struct svc_i3c_master *master)
> +{
> +	u32 reg = 0;

Useless.

> +	writel(SVC_I3C_MCTRL_REQUEST_FORCE_EXIT, master->regs + SVC_I3C_MCTRL);
> +	readl_poll_timeout(master->regs + SVC_I3C_MSTATUS, reg,
> +			   SVC_I3C_MSTATUS_MCTRLDONE(reg), 0, 1000);

No error checks? Why is it okay?
Why is the first parameter 0 while it's not an _atomic() call?

> +	udelay(1);

No explanations given. Also is it really need to be atomic? If not, use
fsleep() and it will choose the best suitable API under the hood.

>  }

...

> +	if (xfer_type == SVC_I3C_MCTRL_TYPE_DDR) {
> +		/* DDR command need prefill into FIFO */
> +		writel(rnw_cmd, master->regs + SVC_I3C_MWDATAB);
> +		if (!rnw) {
> +			/* write data also need prefill into FIFO */
> +			ret = svc_i3c_master_write(master, out, xfer_len);
> +		if (ret)
> +			goto emit_stop;
> +		}

The indentation here is a mess.

> +	}

-- 
With Best Regards,
Andy Shevchenko