[PATCH v2 0/2] dt: i2c: Add support for bus clock

[PATCH v2 0/2] dt: i2c: Add support for bus clock

[Gareth Williams]

The Synopsys I2C Controller has a bus clock that some SoCs require to access
the registers. This series also details the new clock property in the bindings
documentation.

v2:
 - Use new devm_clk_get_optional() function as it simplifies handling when
   the optional clock is not present.

Phil Edworthy (2):
  dt: snps,designware-i2c: Add clock bindings documentation
  i2c: designware: Add support for a bus clock

 Documentation/devicetree/bindings/i2c/i2c-designware.txt |  9 +++++++++
 drivers/i2c/busses/i2c-designware-common.c               | 12 +++++++++++-
 drivers/i2c/busses/i2c-designware-core.h                 |  1 +
 drivers/i2c/busses/i2c-designware-platdrv.c              |  5 +++++
 4 files changed, 26 insertions(+), 1 deletion(-)

-- 
2.7.4

[PATCH v2 1/2] dt: snps,designware-i2c: Add clock bindings documentation

[Gareth Williams]

From: Phil Edworthy <phil.edworthy@renesas.com>

The driver requires an undocumented clock property, so detail it.
Add documentation for a separate, optional, bus clock.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Gareth Williams <gareth.williams.jx@renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
---
v2:
 - No changes.
---
 Documentation/devicetree/bindings/i2c/i2c-designware.txt | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/i2c/i2c-designware.txt b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
index 3e4bcc2..822ebce 100644
--- a/Documentation/devicetree/bindings/i2c/i2c-designware.txt
+++ b/Documentation/devicetree/bindings/i2c/i2c-designware.txt
@@ -6,12 +6,21 @@ Required properties :
                 or "mscc,ocelot-i2c" with "snps,designware-i2c" for fallback
  - reg : Offset and length of the register set for the device
  - interrupts : <IRQ> where IRQ is the interrupt number.
+ - clocks : phandles for the clocks, see the description of clock-names below.
+   The phandle for the "ic_clk" clock is required. The phandle for the "bus"
+   clock is optional. If a single clock is specified but no clock-name, it is
+   the "ic_clk" clock. If both clocks are listed, the "ic_clk" must be first.
 
 Recommended properties :
 
  - clock-frequency : desired I2C bus clock frequency in Hz.
 
 Optional properties :
+
+ - clock-names : Contains the names of the clocks:
+    "ic_clk", for the core clock used to generate the external I2C clock.
+    "bus", the bus clock, sometimes described as pclk, for register accesses.
+
  - reg : for "mscc,ocelot-i2c", a second register set to configure the SDA hold
    time, named ICPU_CFG:TWI_DELAY in the datasheet.
 
-- 
2.7.4

[PATCH v2 2/2] i2c: designware: Add support for a bus clock

[Gareth Williams]

From: Phil Edworthy <phil.edworthy@renesas.com>

The Synopsys I2C Controller has a bus clock, but most SoCs hide this away.
However, on some SoCs you need to explicity enable the bus clock in order
to access the registers. Therefore, add support for an optional bus clock.

Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
Signed-off-by: Gareth Williams <gareth.williams.jx@renesas.com>

---
v2:
 - Use new devm_clk_get_optional() function as it simplifies handling when
   the optional clock is not present.
---
 drivers/i2c/busses/i2c-designware-common.c  | 12 +++++++++++-
 drivers/i2c/busses/i2c-designware-core.h    |  1 +
 drivers/i2c/busses/i2c-designware-platdrv.c |  5 +++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-common.c b/drivers/i2c/busses/i2c-designware-common.c
index a473011..febcea6 100644
--- a/drivers/i2c/busses/i2c-designware-common.c
+++ b/drivers/i2c/busses/i2c-designware-common.c
@@ -251,13 +251,23 @@ unsigned long i2c_dw_clk_rate(struct dw_i2c_dev *dev)
 
 int i2c_dw_prepare_clk(struct dw_i2c_dev *dev, bool prepare)
 {
+	int ret;
+
 	if (IS_ERR(dev->clk))
 		return PTR_ERR(dev->clk);
 
-	if (prepare)
+	if (prepare) {
+		/* Optional bus clock */
+		ret = clk_prepare_enable(dev->busclk);
+		if (ret)
+			return ret;
+
 		return clk_prepare_enable(dev->clk);
+	}
 
 	clk_disable_unprepare(dev->clk);
+	clk_disable_unprepare(dev->busclk);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(i2c_dw_prepare_clk);
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index b4a0b2b..9388ae3 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -226,6 +226,7 @@ struct dw_i2c_dev {
 	void __iomem		*ext;
 	struct completion	cmd_complete;
 	struct clk		*clk;
+	struct clk		*busclk;
 	struct reset_control	*rst;
 	struct i2c_client		*slave;
 	u32			(*get_clk_rate_khz) (struct dw_i2c_dev *dev);
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 9eaac3b..fbaa6aa 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -346,6 +346,11 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
 	else
 		i2c_dw_configure_master(dev);
 
+	/* Optional bus clock */
+	dev->busclk = devm_clk_get_optional(&pdev->dev, "bus");
+	if (IS_ERR(dev->busclk))
+		return PTR_ERR(dev->busclk);
+
 	dev->clk = devm_clk_get(&pdev->dev, NULL);
 	if (!i2c_dw_prepare_clk(dev, true)) {
 		u64 clk_khz;
-- 
2.7.4

Re: [PATCH v2 1/2] dt: snps,designware-i2c: Add clock bindings documentation

[Wolfram Sang]

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On Tue, Feb 19, 2019 at 03:10:41PM +0000, Gareth Williams wrote:
> From: Phil Edworthy <phil.edworthy@renesas.com>
> 
> The driver requires an undocumented clock property, so detail it.
> Add documentation for a separate, optional, bus clock.

Is it named "bus clock" in the datasheets? If so, then be it, but if
possible, I'd avoid this term because it is ambigious (Is it the I2C bus
or the interconnect bus or...?). pclk sounds more precise to me.


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Re: [PATCH v2 2/2] i2c: designware: Add support for a bus clock

[Wolfram Sang]

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> -	if (prepare)
> +	if (prepare) {
> +		/* Optional bus clock */
> +		ret = clk_prepare_enable(dev->busclk);
> +		if (ret)
> +			return ret;
> +
>  		return clk_prepare_enable(dev->clk);

This leaves 'busclk' enabled when the other clock fails.


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