linux-kernel - Re: [PATCH v7 2/2] i2c: spacemit: add support for SpacemiT K1 SoC

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Message-ID: <401059d0-6b2c-4c40-8c4d-51749dca27f3@ieee.org>
Date: Mon, 17 Mar 2025 16:42:51 -0500
From: Alex Elder <elder@...e.org>
To: Troy Mitchell <troymitchell988@...il.com>,
 Andi Shyti <andi.shyti@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Yixun Lan <dlan@...too.org>
Cc: linux-riscv@...ts.infradead.org, linux-i2c@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 spacemit@...ts.linux.dev, Alex Elder <elder@...cstar.com>
Subject: Re: [PATCH v7 2/2] i2c: spacemit: add support for SpacemiT K1 SoC

On 3/16/25 2:43 AM, Troy Mitchell wrote:
> This patch introduces basic I2C support for the SpacemiT K1 SoC,
> utilizing interrupts for transfers.
> 
> The driver has been tested using i2c-tools on a Bananapi-F3 board,
> and basic I2C read/write operations have been confirmed to work.
> 
> Reviewed-by: Alex Elder <elder@...cstar.com>
> Link: https://lore.kernel.org/all/20250128-k1-maintainer-1-v1-1-e5dec4f379eb@gentoo.org [1]
> Signed-off-by: Troy Mitchell <troymitchell988@...il.com>

I know I said it was fine, but I'm going to reiterate two comments in
the probe function.

> ---
>   drivers/i2c/busses/Kconfig  |  17 ++
>   drivers/i2c/busses/Makefile |   1 +
>   drivers/i2c/busses/i2c-k1.c | 605 ++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 623 insertions(+)
> 

. . .

> diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..ae43dcd31e8aa480766b44be91656657c7aaaf4a
> --- /dev/null
> +++ b/drivers/i2c/busses/i2c-k1.c
> @@ -0,0 +1,605 @@

. . .

> +static int spacemit_i2c_probe(struct platform_device *pdev)
> +{
> +	struct clk *clk;
> +	struct device *dev = &pdev->dev;
> +	struct device_node *of_node = pdev->dev.of_node;
> +	struct spacemit_i2c_dev *i2c;
> +	int ret;
> +
> +	i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
> +	if (!i2c)
> +		return -ENOMEM;
> +
> +	ret = of_property_read_u32(of_node, "clock-frequency", &i2c->clock_freq);
> +	if (ret)
> +		dev_warn(dev, "failed to read clock-frequency property\n");

If the property doesn't exist, I don't think this warrants a warning,
because it's optional.  Perhaps if a different error (something other
than -EINVAL) is returned it would warrant a warning.

> +
> +	/* For now, this driver doesn't support high-speed. */
> +	if (!i2c->clock_freq || i2c->clock_freq < 1 ||

For an unsigned value, !i2c->clock_freq is *the same as*
i2c->clock_freq < 1.  Get rid of the latter.

I'll leave it up to the maintainer to decide whether these
comments can just be ignored--my Reviewed-by is fine, even
if you don't change these.

					-Alex

> +	    i2c->clock_freq > SPACEMIT_I2C_MAX_FAST_MODE_FREQ) {
> +		dev_warn(dev, "unsupported clock frequency %u; using %u\n",
> +			 i2c->clock_freq, SPACEMIT_I2C_MAX_FAST_MODE_FREQ);
> +		i2c->clock_freq = SPACEMIT_I2C_MAX_FAST_MODE_FREQ;
> +	} else if (i2c->clock_freq < SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ) {
> +		dev_warn(dev, "unsupported clock frequency %u; using %u\n",
> +			 i2c->clock_freq,  SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ);
> +		i2c->clock_freq = SPACEMIT_I2C_MAX_STANDARD_MODE_FREQ;
> +	}
> +
> +	i2c->dev = &pdev->dev;
> +
> +	i2c->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(i2c->base))
> +		return dev_err_probe(dev, PTR_ERR(i2c->base), "failed to do ioremap");
> +
> +	i2c->irq = platform_get_irq(pdev, 0);
> +	if (i2c->irq < 0)
> +		return dev_err_probe(dev, i2c->irq, "failed to get irq resource");
> +
> +	ret = devm_request_irq(i2c->dev, i2c->irq, spacemit_i2c_irq_handler,
> +			       IRQF_NO_SUSPEND | IRQF_ONESHOT, dev_name(i2c->dev), i2c);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "failed to request irq");
> +
> +	clk = devm_clk_get_enabled(dev, "func");
> +	if (IS_ERR(clk))
> +		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable func clock");
> +
> +	clk = devm_clk_get_enabled(dev, "bus");
> +	if (IS_ERR(clk))
> +		return dev_err_probe(dev, PTR_ERR(clk), "failed to enable bus clock");
> +
> +	spacemit_i2c_reset(i2c);
> +
> +	i2c_set_adapdata(&i2c->adapt, i2c);
> +	i2c->adapt.owner = THIS_MODULE;
> +	i2c->adapt.algo = &spacemit_i2c_algo;
> +	i2c->adapt.dev.parent = i2c->dev;
> +	i2c->adapt.nr = pdev->id;
> +
> +	i2c->adapt.dev.of_node = of_node;
> +
> +	strscpy(i2c->adapt.name, "spacemit-i2c-adapter", sizeof(i2c->adapt.name));
> +
> +	init_completion(&i2c->complete);
> +
> +	platform_set_drvdata(pdev, i2c);
> +
> +	ret = i2c_add_numbered_adapter(&i2c->adapt);
> +	if (ret)
> +		return dev_err_probe(&pdev->dev, ret, "failed to add i2c adapter");
> +
> +	return 0;
> +}
> +
> +static void spacemit_i2c_remove(struct platform_device *pdev)
> +{
> +	struct spacemit_i2c_dev *i2c = platform_get_drvdata(pdev);
> +
> +	i2c_del_adapter(&i2c->adapt);
> +}
> +
> +static const struct of_device_id spacemit_i2c_of_match[] = {
> +	{ .compatible = "spacemit,k1-i2c", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, spacemit_i2c_of_match);
> +
> +static struct platform_driver spacemit_i2c_driver = {
> +	.probe = spacemit_i2c_probe,
> +	.remove = spacemit_i2c_remove,
> +	.driver = {
> +		.name = "i2c-k1",
> +		.of_match_table = spacemit_i2c_of_match,
> +	},
> +};
> +module_platform_driver(spacemit_i2c_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("I2C bus driver for SpacemiT K1 SoC");
>