Patchwork [2/2] i2c designware add support of I2C standard mode

login
register
mail settings
Submitter Romain Baeriswyl
Date Oct. 8, 2013, 3 p.m.
Message ID <1381244455-3836-2-git-send-email-romainba@abilis.com>
Download mbox | patch
Permalink /patch/281499/
State Changes Requested
Headers show

Comments

Romain Baeriswyl - Oct. 8, 2013, 3 p.m.
Some legacy devices support ony I2C standard mode at 100kHz. 
This patch allows to select the standard mode through the DTS 
with the use of the existing clock-frequency parameter.

When clock-frequency parameter is not set, the fast mode is selected.
Only when the parameter is set at 100000, the standard mode is selected.

Signed-off-by: Romain Baeriswyl <romainba@abilis.com>
Reviewed-by: Christian Ruppert <christian.ruppert@abilis.com>
---
 .../devicetree/bindings/i2c/i2c-designware.txt     |    1 +
 drivers/i2c/busses/i2c-designware-platdrv.c        |   17 +++++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)
Mika Westerberg - Oct. 9, 2013, 7:56 a.m.
On Tue, Oct 08, 2013 at 05:00:55PM +0200, Romain Baeriswyl wrote:
> Some legacy devices support ony I2C standard mode at 100kHz. 
> This patch allows to select the standard mode through the DTS 
> with the use of the existing clock-frequency parameter.
> 
> When clock-frequency parameter is not set, the fast mode is selected.
> Only when the parameter is set at 100000, the standard mode is selected.
> 
> Signed-off-by: Romain Baeriswyl <romainba@abilis.com>
> Reviewed-by: Christian Ruppert <christian.ruppert@abilis.com>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Shinya Kuribayashi - Oct. 13, 2013, 11:46 a.m.
On 10/9/13 4:56 PM, Mika Westerberg wrote:> On Tue, Oct 08, 2013 at 05:00:55PM +0200, Romain Baeriswyl wrote:
>> Some legacy devices support ony I2C standard mode at 100kHz.
>> This patch allows to select the standard mode through the DTS
>> with the use of the existing clock-frequency parameter.
>>
>> When clock-frequency parameter is not set, the fast mode is selected.
>> Only when the parameter is set at 100000, the standard mode is selected.
>>
>> Signed-off-by: Romain Baeriswyl <romainba@abilis.com>
>> Reviewed-by: Christian Ruppert <christian.ruppert@abilis.com>
>
> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

I don't have build environment for these patches right now, but both
changes 1/2 and 2/2 look good.

It's quite reasonable and makes the code readable to convert
{3 => 300} into nsec based one.  I should have done so from the
beginning, thanks for doing this.

   Shinya

--
To unsubscribe from this list: send the line "unsubscribe linux-i2c" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Wolfram Sang - Jan. 16, 2014, 7:33 p.m.
On Tue, Oct 08, 2013 at 05:00:55PM +0200, Romain Baeriswyl wrote:
> Some legacy devices support ony I2C standard mode at 100kHz. 
> This patch allows to select the standard mode through the DTS 
> with the use of the existing clock-frequency parameter.
> 
> When clock-frequency parameter is not set, the fast mode is selected.
> Only when the parameter is set at 100000, the standard mode is selected.
> 
> Signed-off-by: Romain Baeriswyl <romainba@abilis.com>
> Reviewed-by: Christian Ruppert <christian.ruppert@abilis.com>

Pretty much OK. One change needed, though:

> ---
>  .../devicetree/bindings/i2c/i2c-designware.txt     |    1 +
>  drivers/i2c/busses/i2c-designware-platdrv.c        |   17 +++++++++++++++--
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> index 5199b0c..16d0bef 100644
> --- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> +++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
> @@ -9,6 +9,7 @@ Required properties :
>  Recommended properties :
>  
>   - clock-frequency : desired I2C bus clock frequency in Hz.
> +   Only standard mode at 100kHz and fast mode at 400kHz are supported.

This should not go the bindings doc, since this is a linux specific
detail. It should go...

> +		if (clk_freq != 100000 && clk_freq != 400000)
> +			return -EINVAL;

... here as an dev_err message "Only x and y supported".

Rest looks good, thanks!

Patch

diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
index 5199b0c..16d0bef 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
@@ -9,6 +9,7 @@  Required properties :
 Recommended properties :
 
  - clock-frequency : desired I2C bus clock frequency in Hz.
+   Only standard mode at 100kHz and fast mode at 400kHz are supported.
 
 Optional properties :
  - i2c-sda-hold-time-ns : should contain the SDA hold time in nanoseconds.
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 0d6fe47..5f06848 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -87,6 +87,7 @@  static int dw_i2c_probe(struct platform_device *pdev)
 	struct i2c_adapter *adap;
 	struct resource *mem;
 	int irq, r;
+	u32 clk_freq;
 
 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0) {
@@ -122,6 +123,9 @@  static int dw_i2c_probe(struct platform_device *pdev)
 		return PTR_ERR(dev->clk);
 	clk_prepare_enable(dev->clk);
 
+	/* fast mode by default */
+	clk_freq = 400000;
+
 	if (pdev->dev.of_node) {
 		u32 ht = 0;
 		u32 ic_clk = dev->get_clk_rate_khz(dev);
@@ -136,6 +140,11 @@  static int dw_i2c_probe(struct platform_device *pdev)
 		of_property_read_u32(pdev->dev.of_node,
 				     "i2c-scl-falling-time-ns",
 				     &dev->scl_falling_time);
+
+		of_property_read_u32(pdev->dev.of_node, "clock-frequency",
+				     &clk_freq);
+		if (clk_freq != 100000 && clk_freq != 400000)
+			return -EINVAL;
 	}
 
 	dev->functionality =
@@ -145,8 +154,12 @@  static int dw_i2c_probe(struct platform_device *pdev)
 		I2C_FUNC_SMBUS_BYTE_DATA |
 		I2C_FUNC_SMBUS_WORD_DATA |
 		I2C_FUNC_SMBUS_I2C_BLOCK;
-	dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
-		DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
+	if (clk_freq == 100000)
+		dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
+			DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_STD;
+	else
+		dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
+			DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
 
 	/* Try first if we can configure the device from ACPI */
 	r = dw_i2c_acpi_configure(pdev);