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Date: Mon, 4 Nov 2013 15:28:23 +0100
From: Maxime Coquelin <maxime.coquelin@...com>
To: Wolfram Sang <wsa@...-dreams.de>
Cc: <srinivas.kandagatla@...com>,
Rob Herring <rob.herring@...xeda.com>,
Pawel Moll <pawel.moll@....com>,
Mark Rutland <mark.rutland@....com>,
Stephen Warren <swarren@...dotorg.org>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Rob Landley <rob@...dley.net>,
Russell King <linux@....linux.org.uk>,
Grant Likely <grant.likely@...aro.org>,
<devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-i2c@...r.kernel.org>, <stephen.gallimore@...com>,
<stuart.menefy@...com>, Lee Jones <lee.jones@...aro.org>,
<gabriel.fernandez@...com>
Subject: Re: [PATCH v5 1/4] i2c: busses: i2c-st: Add ST I2C controller
Hi Wolfram,
On 11/01/2013 12:16 PM, Wolfram Sang wrote:
> Hi,
>
...
>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-st.txt b/Documentation/devicetree/bindings/i2c/i2c-st.txt
>> new file mode 100644
>> index 0000000..8b2fd0b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/i2c/i2c-st.txt
>> @@ -0,0 +1,38 @@
>> +ST SSC binding, for I2C mode operation
>> +
>> +Required properties :
>> +- compatible : Must be "st,comms-i2c"
>
> I personally don't care about naming here. Has there been a solution
> now?
Srini proposes to add 2 compatible strings, as the IP is compatible with
two SSC IPs:
"st,comms-ssc-i2c"
"st,comms-ssc4-i2c"
>> +
>> +Optional properties :
>> +- clock-frequency : Desired I2C bus clock frequency in Hz. If not specified,
>> + the default 100 kHz frequency will be used. As only Normal and Fast modes
>> + are supported, possible values are 100000 and 400000.
>> +- i2c-min-scl-pulse-width-us : The minimum valid SCL pulse width that is
>> + allowed through the deglitch circuit. In units of us.
>> +- i2c-min-sda-pulse-width-us : The minimum valid SDA pulse width that is
>> + allowed through the deglitch circuit. In units of us.
>
> Okay, so we had lots of dt bindings discussions at kernel summit. Since
> we don't have unstable bindings yet, I have been convinced that it is
> okay two have one or two vendor specific bindings before introducing a
> generic one. That will create a little bit of cruft, but increases
> chances that the generic bindings are proper. So, really sorry for going
> back and forth, but it was important for the process. Vendor binding is
> it now. Period.
>
> ...
No problem wolfram! Thanks for clarifying this thing.
>
>> +/**
>> + * struct st_i2c_deglitch - Anti-glitch filter configuration
>> + * @scl_min_width_us: SCL line minimum pulse width in ns
>> + * @sda_min_width_us: SDA line minimum pulse width in ns
>> + */
>> +struct st_i2c_deglitch {
>> + u32 scl_min_width_us;
>> + u32 sda_min_width_us;
>> +};
>
> Minor: Why a seperate struct?
This not needed, I will move its fields into st_i2c_dev struct.
>
>> +/**
>> + * st_i2c_handle_write() - Handle FIFO enmpty interrupt in case of read
>> + * @i2c_dev: Controller's private data
>> + */
>> +static void st_i2c_handle_read(struct st_i2c_dev *i2c_dev)
>> +{
>> + struct st_i2c_client *c = &i2c_dev->client;
>> + u32 ien;
>> +
>> + /* Trash the address read back */
>> + if (!c->xfered) {
>> + readl(i2c_dev->base + SSC_RBUF);
>> + st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_TXENB);
>> + } else
>> + st_i2c_read_rx_fifo(i2c_dev);
>
> Braces around else branch.
Okay
>
>> +
>> + if (!c->count) {
>> + /* End of xfer, send stop or repstart */
>> + st_i2c_terminate_xfer(i2c_dev);
>> + } else if (c->count == 1) {
>> + /* Penultimate byte to xfer, disable ACK gen. */
>> + st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_ACKG);
>> +
>> + /* Last received byte is to be handled by NACK interrupt */
>> + ien = SSC_IEN_NACKEN | SSC_IEN_ARBLEN;
>> + writel(ien, i2c_dev->base + SSC_IEN);
>> +
>> + st_i2c_rd_fill_tx_fifo(i2c_dev, c->count);
>> + } else
>> + st_i2c_rd_fill_tx_fifo(i2c_dev, c->count - 1);
>
> Braces around else branch.
Ditto
>
>> +}
>> +static int st_i2c_probe(struct platform_device *pdev)
>> +{
>> + struct device_node *np = pdev->dev.of_node;
>> + struct st_i2c_dev *i2c_dev;
>> + struct resource *res;
>> + u32 clk_rate;
>> + struct i2c_adapter *adap;
>> + int ret;
>> +
>> + i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
>> + if (!i2c_dev)
>> + return -ENOMEM;
>> +
>> + res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> + i2c_dev->base = devm_ioremap_resource(&pdev->dev, res);
>> + if (IS_ERR(i2c_dev->base))
>> + return PTR_ERR(i2c_dev->base);
>> +
>> + i2c_dev->irq = irq_of_parse_and_map(np, 0);
>> + if (!i2c_dev->irq) {
>> + dev_err(&pdev->dev, "IRQ missing or invalid\n");
>> + return -EINVAL;
>> + }
>> +
>> + i2c_dev->clk = of_clk_get_by_name(np, "ssc");
>> + if (IS_ERR(i2c_dev->clk)) {
>> + dev_err(&pdev->dev, "Unable to request clock\n");
>> + return PTR_ERR(i2c_dev->clk);
>> + }
>> +
>> + i2c_dev->mode = I2C_MODE_STANDARD;
>> + ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
>> + if ((!ret) && (clk_rate == 400000))
>> + i2c_dev->mode = I2C_MODE_FAST;
>> +
>> + i2c_dev->dev = &pdev->dev;
>> +
>> + ret = devm_request_irq(&pdev->dev, i2c_dev->irq, st_i2c_isr, 0,
>> + pdev->name, i2c_dev);
>
> Suggestion: Maybe threaded irq since you do fifo handling in the isr?
That's a good point, I will switch to threaded irq.
>
>> + if (ret) {
>> + dev_err(&pdev->dev, "Failed to request irq %i\n", i2c_dev->irq);
>> + return ret;
>> + }
>> +
>> + pinctrl_pm_select_default_state(i2c_dev->dev);
>> + /* In case idle state available, select it */
>> + pinctrl_pm_select_idle_state(i2c_dev->dev);
>> +
>> + ret = st_i2c_of_get_deglitch(np, i2c_dev);
>> + if (ret)
>> + return ret;
>> +
>> + adap = &i2c_dev->adap;
>> + i2c_set_adapdata(adap, i2c_dev);
>> + snprintf(adap->name, sizeof(adap->name), "ST I2C(0x%08x)", res->start);
>
> resource_size_t can also be 64 bit.
Okay, I will change to 0x%x
>
>> + adap->owner = THIS_MODULE;
>> + adap->timeout = 2 * HZ;
>> + adap->retries = 0;
>> + adap->class = I2C_CLASS_HWMON | I2C_CLASS_DDC | I2C_CLASS_SPD;
>
> This question is still open:
> Why do you need class based instantiation. It will most likely cost
> boot-time and you have devicetree means for doing instantiation.
Sorry, I missed to take your remark into account last time...
This is indeed useless and adds a cost at boot time, it will be removed
in next series.
>
>> + adap->algo = &st_i2c_algo;
>> + adap->dev.parent = &pdev->dev;
>> + adap->dev.of_node = pdev->dev.of_node;
>> +
>> + init_completion(&i2c_dev->complete);
>> +
>> + ret = i2c_add_adapter(adap);
>> + if (ret) {
>> + dev_err(&pdev->dev, "Failed to add adapter\n");
>> + return ret;
>> + }
>> +
>> + platform_set_drvdata(pdev, i2c_dev);
>> +
>> + dev_info(i2c_dev->dev, "%s initialized\n", adap->name);
>> +
>> + return 0;
>> +}
>> +
>
> Rest looks good! We are mostly ready to go.
Perfect! :)
I will try to send a new series this week.
Thanks,
Maxime
>
> Thanks,
>
> Wolfram
>
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