linux-kernel - Re: [PATCH v6 1/2] i2c: add support for microchip fpga i2c controllers

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Date:   Wed, 6 Jul 2022 09:19:20 +0200
From:   Wolfram Sang <wsa@...nel.org>
To:     Conor Dooley <conor.dooley@...rochip.com>
Cc:     linux-i2c@...r.kernel.org, ben.dooks@...ethink.co.uk,
        linux-kernel@...r.kernel.org, linux-riscv@...ts.infradead.org,
        daire.mcnamara@...rochip.com
Subject: Re: [PATCH v6 1/2] i2c: add support for microchip fpga i2c
 controllers

Hi Conor,

thank you for sending this driver.

On Tue, Jun 21, 2022 at 08:42:38AM +0100, Conor Dooley wrote:
> Add Microchip CoreI2C i2c controller support. This driver supports the
> "hard" i2c controller on the Microchip PolarFire SoC & the basic feature
> set for "soft" i2c controller implemtations in the FPGA fabric.
> 
> Co-developed-by: Daire McNamara <daire.mcnamara@...rochip.com>
> Signed-off-by: Daire McNamara <daire.mcnamara@...rochip.com>
> Signed-off-by: Conor Dooley <conor.dooley@...rochip.com>

Where are the bindings? Are they already on the way upstream?

>  drivers/i2c/busses/i2c-microchip-core.c | 486 ++++++++++++++++++++++++

The biggest remark I have is to rename the driver a little. Usually a
"-core" suffix means that there are other drivers like "-platform" or
"-pci" use this core. Would "i2c-microchip-fpga" or
"i2c-microchip-corei2c" work for you?

> +#include <linux/clk.h>
> +#include <linux/clkdev.h>
> +#include <linux/err.h>
> +#include <linux/i2c.h>
> +#include <linux/iopoll.h>

Do you really need that?

...

> +static irqreturn_t mchp_corei2c_handle_isr(struct mchp_corei2c_dev *idev)
> +{
> +	u32 status = idev->isr_status;
> +	u8 ctrl;
> +	bool last_byte = false, finished = false;
> +
> +	if (!idev->buf)
> +		return IRQ_NONE;
> +
> +	switch (status) {
> +	case STATUS_M_START_SENT:
> +	case STATUS_M_REPEATED_START_SENT:
> +		ctrl = readb(idev->base + CORE_I2C_CTRL);
> +		ctrl &= ~CTRL_STA;
> +		writeb(idev->addr, idev->base + CORE_I2C_DATA);
> +		writeb(ctrl, idev->base + CORE_I2C_CTRL);
> +		if (idev->msg_len <= 0)
> +			finished = true;

How can it happen that len is < 0? Wouldn't that be an error case?

...

> +static u32 mchp_corei2c_func(struct i2c_adapter *adap)
> +{
> +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;

Have you testes SMBUS_QUICK as well?

...

> +	idev->dev = &pdev->dev;
> +	init_completion(&idev->msg_complete);
> +	spin_lock_init(&idev->lock);

You never use this lock.

...

> +	idev->adapter.owner = THIS_MODULE;
> +	idev->adapter.algo = &mchp_corei2c_algo;
> +	idev->adapter.dev.parent = &pdev->dev;
> +	idev->adapter.dev.of_node = pdev->dev.of_node;
> +	idev->adapter.timeout = MICROCHIP_I2C_TIMEOUT;

Simply use HZ here?

All in all, only minor stuff. Driver looks really good in general.

Thanks and happy hacking,

   Wolfram


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