linux-kernel - Re: [PATCH 1/3] i2c: tegra: implement slave mode

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Message-ID: <20150129114155.GA9080@katana>
Date:	Thu, 29 Jan 2015 12:41:55 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Andrey Danin <danindrey@...l.ru>
Cc:	linux-i2c@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	ac100@...ts.launchpad.net, Laxman Dewangan <ldewangan@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>,
	Marc Dietrich <marvin24@....de>
Subject: Re: [PATCH 1/3] i2c: tegra: implement slave mode

Hi,

> Initialization code is based on NVEC driver.
> 
> There is a HW bug in AP20 that was also mentioned in kernel sources
> for Toshiba AC100.
> 
> Signed-off-by: Andrey Danin <danindrey@...l.ru>

Cool, thanks for the converison. While I usually like to only get the
patches which I need to handle, please CC me to all patches next time. I
am interested what changes were needed for the user of the slave
framework, too.

> +static bool tegra_i2c_slave_isr(int irq, struct tegra_i2c_dev *i2c_dev)
> +{
> +	unsigned long status;
> +	u8 value;
> +
> +	if (!i2c_dev->slave || !i2c_dev->slave->slave_cb)
> +		return false;

Can this happen?

> +	/* i2c master sends data to us */
> +	if (is_write(status)) {
> +		i2c_slave_event(i2c_dev->slave, I2C_SLAVE_REQ_WRITE_START,
> +				NULL);

Can this HW create an interrupt once the address detection + RW bit are
received? Or only if a complete write has been received?

> +static int tegra_reg_slave(struct i2c_client *slave)
> +{
> +	struct tegra_i2c_dev *i2c_dev = i2c_get_adapdata(slave->adapter);
> +
> +	if (i2c_dev->slave)
> +		return -EBUSY;
> +
> +	i2c_dev->slave = slave;
> +
> +	tegra_i2c_clock_enable(i2c_dev);
> +
> +	reset_control_assert(i2c_dev->rst);
> +	udelay(2);
> +	reset_control_deassert(i2c_dev->rst);

Why do you need a reset when a slave gets registered?

> +
> +	i2c_writel(i2c_dev, I2C_SL_CNFG_NEWSL, I2C_SL_CNFG);
> +	i2c_writel(i2c_dev, 0x1E, I2C_SL_DELAY_COUNT);

What does this magic number mean?

> +
> +	i2c_writel(i2c_dev, slave->addr, I2C_SL_ADDR1);
> +	i2c_writel(i2c_dev, 0, I2C_SL_ADDR2);

Handling 10 bit addresses?

> +
> +	return 0;
> +}
> +

>  static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
> @@ -679,6 +808,7 @@ static const struct tegra_i2c_hw_feature tegra30_i2c_hw = {
>  	.has_single_clk_source = false,
>  	.clk_divisor_hs_mode = 3,
>  	.clk_divisor_std_fast_mode = 0,
> +	.slave_read_start_delay = 0,

No need to init to 0 IMO.


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