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:

quoted

[...]

quoted

From: Lee Jones<redacted>
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 at vger.kernel.org
Signed-off-by: Lee Jones<redacted>
---
  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.

quoted

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.

quoted

quoted

+};
+
+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 :)

quoted

	/*
	 * 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.

quoted

quoted

+
+       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.

quoted

quoted

+
        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
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