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Message-ID: <4FDB3642.5030804@linaro.org>
Date: Fri, 15 Jun 2012 14:18:58 +0100
From: Lee Jones <lee.jones@...aro.org>
To: Srinidhi Kasagar <srinidhi.kasagar@...ricsson.com>
CC: Linus WALLEIJ <linus.walleij@...ricsson.com>,
"arnd@...db.de" <arnd@...db.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"grant.likely@...retlab.ca" <grant.likely@...retlab.ca>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>
Subject: Re: Fwd: [PATCH 1/3] i2c: Add Device Tree support to the Nomadik
I2C driver
On 15/06/12 14:05, Srinidhi Kasagar wrote:
> On Fri, Jun 15, 2012 at 14:45:11 +0200, Lee Jones wrote:
>> On 15/06/12 12:50, Srinidhi Kasagar wrote:
>>> [...]
>>>>
>>>>
>>>> From: Lee Jones<lee.jones@...aro.org>
>>>> Date: Tue, 17 Apr 2012 16:04:13 +0100
>>>> Subject: [PATCH 1/1] i2c: Add Device Tree support to the Nomadik I2C driver
>>>>
>>>> Here we apply the bindings required for successful Device Tree
>>>> probing of the i2c-nomadik driver. We also apply a fall-back
>>>> configuration in case either one is not provided, or a required
>>>> element is missing from the one supplied.
>>>>
>>>> Cc: linux-i2c@...r.kernel.org
>>>> Signed-off-by: Lee Jones<lee.jones@...aro.org>
>>>> ---
>>>> drivers/i2c/busses/i2c-nomadik.c | 82 +++++++++++++++++++++++++++++++++++++-
>>>> 1 file changed, 80 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-nomadik.c b/drivers/i2c/busses/i2c-nomadik.c
>>>> index a92440d..58e8114 100644
>>>> --- a/drivers/i2c/busses/i2c-nomadik.c
>>>> +++ b/drivers/i2c/busses/i2c-nomadik.c
>>>> @@ -23,6 +23,7 @@
>>>> #include<linux/io.h>
>>>> #include<linux/regulator/consumer.h>
>>>> #include<linux/pm_runtime.h>
>>>> +#include<linux/of.h>
>>>>
>>>> #include<plat/i2c.h>
>>>>
>>>> @@ -899,15 +900,86 @@ static const struct i2c_algorithm nmk_i2c_algo = {
>>>> .functionality = nmk_i2c_functionality
>>>> };
>>>>
>>>> +static struct nmk_i2c_controller u8500_i2c = {
>>>> + /*
>>>> + * Slave data setup time; 250ns, 100ns, and 10ns, which
>>>> + * is 14, 6 and 2 respectively for a 48Mhz i2c clock.
>>>> + */
>>>> + .slsu = 0xe,
>>>> + .tft = 1, /* Tx FIFO threshold */
>>>> + .rft = 8, /* Rx FIFO threshold */
>>>> + .clk_freq = 100000, /* std. mode operation */
>>>> + .timeout = 200, /* Slave response timeout(ms) */
>>>> + .sm = I2C_FREQ_MODE_FAST,
>>>
>>> How is this possible? you are setting clk_freq as 100kb/s and mode
>>> as fast mode which is supposed to be 400kb/s.
>>
>> That's not how I read it:
>
> But it is not readable. It confuses people.
I understood it. :)
If you think it's unclear speak to the author, Linus. He's CC'ed.
>>> enum i2c_freq_mode {
>>> I2C_FREQ_MODE_STANDARD, /* up to 100 Kb/s */
>>> I2C_FREQ_MODE_FAST, /* up to 400 Kb/s */
>>> I2C_FREQ_MODE_HIGH_SPEED, /* up to 3.4 Mb/s */
>>> I2C_FREQ_MODE_FAST_PLUS, /* up to 1 Mb/s */
>>> };
>>
>> The operative words here are "up to".
>
> I know, then none of these modes does not make sense.
>
>>>> +};
>>>> +
>>>> +static int __devinit
>>>> +nmk_i2c_of_probe(struct device_node *np, struct nmk_i2c_controller *pdata)
>>>> +{
>>>> + of_property_read_u32(np, "clock-frequency", (u32*)&pdata->clk_freq);
>>>> + if (!pdata->clk_freq) {
>>>> + pr_warn("%s: Clock frequency not found\n", np->full_name);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + of_property_read_u32(np, "stericsson,slsu", (u32*)&pdata->slsu);
>>>> + if (!pdata->slsu) {
>>>> + pr_warn("%s: Data line delay not found\n", np->full_name);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + of_property_read_u32(np, "stericsson,tft", (u32*)&pdata->tft);
>>>> + if (!pdata->tft) {
>>>> + pr_warn("%s: Tx FIFO threshold not found\n", np->full_name);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + of_property_read_u32(np, "stericsson,rft", (u32*)&pdata->rft);
>>>> + if (!pdata->rft) {
>>>> + pr_warn("%s: Rx FIFO threshold not found\n", np->full_name);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + of_property_read_u32(np, "stericsson,timeout", (u32*)&pdata->timeout);
>>>> + if (!pdata->timeout) {
>>>> + pr_warn("%s: Timeout not found\n", np->full_name);
>>>> + return -EINVAL;
>>>> + }
>>>> +
>>>> + if (of_get_property(np, "stericsson,i2c_freq_mode_fast", NULL))
>>>> + pdata->sm = I2C_FREQ_MODE_FAST;
>>>> + else
>>>> + pdata->sm = I2C_FREQ_MODE_STANDARD;
>>>
>>> The controller has more modes like fast mode plus and high speed mode. You can't make
>>> assumptions like this.
>>
>> These are currently unsupported. Read the comments in the file:
>
> I wrote this code, I remember these comments very well :)
Yes, I saw. I thought that perhaps you'd forgotten. ;)
>>> /*
>>> * set the speed mode. Currently we support
>>> * only standard and fast mode of operation
>>> * TODO - support for fast mode plus (up to 1Mb/s)
>>> * and high speed (up to 3.4 Mb/s)
>>> */
>>
>> I can add a similar comment here if it make you feel better?
>
> Please.
No problem.
>>>> +
>>>> + return 0;
>>>> +}
>>>> +
>>>> static int __devinit nmk_i2c_probe(struct platform_device *pdev)
>>>> {
>>>> int ret = 0;
>>>> struct resource *res;
>>>> - struct nmk_i2c_controller *pdata =
>>>> - pdev->dev.platform_data;
>>>> + struct nmk_i2c_controller *pdata = pdev->dev.platform_data;
>>>> + struct device_node *np = pdev->dev.of_node;
>>>> struct nmk_i2c_dev *dev;
>>>> struct i2c_adapter *adap;
>>>>
>>>> + if (np) {
>>>> + if (!pdata) {
>>>> + pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
>>>> + if (!pdata) {
>>>> + ret = -ENOMEM;
>>>> + goto err_no_mem;
>>>> + }
>>>> + }
>>>> + ret = nmk_i2c_of_probe(np, pdata);
>>>> + if (ret)
>>>> + kfree(pdata);
>>>> + }
>>>> +
>>>> + if (!pdata)
>>>> + /* No i2c configuration found, using the default. */
>>>> + pdata =&u8500_i2c;
>>>
>>> There are redundant fallback configurations exists in the driver. You might need to remove
>>> those, if you want to fallback here.
>>
>> I only see a fall-back for clk_freq. Are there others?
>
> No, I can see that it only exists in setup_i2c_controller(). Please fix.
I can remove it, no problem.
>>>> +
>>>> dev = kzalloc(sizeof(struct nmk_i2c_dev), GFP_KERNEL);
>>>> if (!dev) {
>>>> dev_err(&pdev->dev, "cannot allocate memory\n");
>>>> @@ -1038,11 +1110,17 @@ static int __devexit nmk_i2c_remove(struct platform_device *pdev)
>>>> return 0;
>>>> }
>>>>
>>>> +static const struct of_device_id nmk_gpio_match[] = {
>>>> + { .compatible = "st,nomadik-i2c", },
>>>> + {},
>>>> +};
>>>> +
>>>> static struct platform_driver nmk_i2c_driver = {
>>>> .driver = {
>>>> .owner = THIS_MODULE,
>>>> .name = DRIVER_NAME,
>>>> .pm =&nmk_i2c_pm,
>>>> + .of_match_table = nmk_gpio_match,
>>>> },
>>>> .probe = nmk_i2c_probe,
>>>> .remove = __devexit_p(nmk_i2c_remove),
>>>> --
>>>> 1.7.9.5
>>>>
--
Lee Jones
Linaro ST-Ericsson Landing Team Lead
M: +44 77 88 633 515
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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