linux-kernel - Re: [PATCH v7 2/3] I2C: mediatek: Add driver for MediaTek I2C controller

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Date:	Tue, 12 May 2015 14:58:32 +0200
From:	wsa@...-dreams.de
To:	Eddie Huang <eddie.huang@...iatek.com>
Cc:	Sascha Hauer <kernel@...gutronix.de>, srv_heupstream@...iatek.com,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Jean Delvare <jdelvare@...e.de>,
	David Box <david.e.box@...ux.intel.com>,
	Doug Anderson <dianders@...omium.org>,
	Zhangfei Gao <zhangfei.gao@...aro.org>,
	Max Schwarz <max.schwarz@...ine.de>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Anders Berg <anders.berg@...gotech.com>,
	Neelesh Gupta <neelegup@...ux.vnet.ibm.com>,
	Lee Jones <lee.jones@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Ray Jui <rjui@...adcom.com>,
	Simon Glass <sjg@...omium.org>,
	Wei Yan <sledge.yanwei@...wei.com>,
	Beniamino Galvani <b.galvani@...il.com>,
	Xudong Chen <xudong.chen@...iatek.com>,
	Liguo Zhang <liguo.zhang@...iatek.com>,
	linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v7 2/3] I2C: mediatek: Add driver for MediaTek I2C
 controller

> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/sched.h>
> +#include <linux/delay.h>
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/device.h>
> +#include <linux/platform_device.h>
> +#include <linux/mm.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/scatterlist.h>
> +#include <linux/io.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/clk.h>
> +#include <linux/completion.h>

Please sort the includes to avoid duplicates.

> +struct mtk_i2c_compatible {
> +	const struct i2c_adapter_quirks *quirks;
> +	unsigned char pmic_i2c;
> +	unsigned char dcm;
> +};

I wonder if the unsigned char options can be bits in a flags variable?

> +static const struct i2c_adapter_quirks mt6577_i2c_quirks = {
> +	.flags = I2C_AQ_COMB_WRITE_THEN_READ,
> +	.max_num_msgs = MAX_MSG_NUM_MT6577,
> +	.max_write_len = MAX_DMA_TRANS_SIZE_MT6577,
> +	.max_read_len = MAX_DMA_TRANS_SIZE_MT6577,
> +	.max_comb_1st_msg_len = MAX_DMA_TRANS_SIZE_MT6577,
> +	.max_comb_2nd_msg_len = MAX_WRRD_TRANS_SIZE_MT6577,
> +};

I would think plain numbers are much more readable than defines here.
They are used only once, too.

> +static const struct of_device_id mtk_i2c_of_match[] = {
> +	{ .compatible = "mediatek,mt6577-i2c", .data = (void *)&mt6577_compat },
> +	{ .compatible = "mediatek,mt6589-i2c", .data = (void *)&mt6589_compat },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, mtk_i2c_of_match);

No need for casts.

> +static inline void mtk_i2c_writew(u16 value, struct mtk_i2c *i2c, u8 offset)
> +{
> +	writew(value, i2c->base + offset);
> +}
> +
> +static inline u16 mtk_i2c_readw(struct mtk_i2c *i2c, u8 offset)
> +{
> +	return readw(i2c->base + offset);
> +}

I am not a big fan of such extremly thin wrappers, but if you like them...

> +		rpaddr = dma_map_single(i2c->adap.dev.parent, msgs->buf,
> +						msgs->len, DMA_FROM_DEVICE);

I think you shouldn't use the adapter device here and later, but the dma
channel device.

> +	/* flush before sending start */
> +	mb();
> +	mtk_i2c_writel_dma(I2C_DMA_START_EN, i2c, OFFSET_EN);

Is mb() really needed when you use writel after that?

> +	if (i2c->irq_stat & (I2C_HS_NACKERR | I2C_ACKERR)) {
> +		dev_dbg(i2c->dev, "addr: %x, transfer ACK error\n", msgs->addr);
> +		mtk_i2c_init_hw(i2c);
> +		return -EREMOTEIO;

-ENXIO. Please check Documentation/i2c/fault-codes for a reference and
check all your error values.

> +	ret = of_property_read_u32(np, "clock-div", clk_src_div);
> +	if (ret < 0)
> +		return ret;

Do we need a property for that in the i2c-block? Can't the clock
provider driver deliver a properly divided clock already?


And cppcheck says:

drivers/i2c/busses/i2c-mt65xx.c:133: style: struct or union member 'mtk_i2c_data::clk_frequency' is never used.
drivers/i2c/busses/i2c-mt65xx.c:135: style: struct or union member 'mtk_i2c_data::clk_src_div' is never used.

Rest looks good, thanks!


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