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Date: Fri, 15 Jun 2012 13:45:11 +0100
From: Lee Jones <lee.jones@...aro.org>
To: Srinidhi Kasagar <srinidhi.kasagar@...ricsson.com>
CC: linus.walleij@...ricsson.com, arnd@...db.de,
linux-kernel@...r.kernel.org, grant.likely@...retlab.ca,
linux-arm-kernel@...ts.infradead.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 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:
> 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".
>> +};
>> +
>> +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:
> /*
> * 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?
>> +
>> + 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?
>> +
>> 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
>>
Kind regards,
Lee
--
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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