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Message-ID: <20120615130544.GA28537@bnru02>
Date: Fri, 15 Jun 2012 18:35:46 +0530
From: Srinidhi Kasagar <srinidhi.kasagar@...ricsson.com>
To: Lee Jones <lee.jones@...aro.org>
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 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.
>
> > 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 :)
>
> > /*
> > * 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.
>
> >> +
> >> + 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.
>
> >> +
> >> 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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