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Subject[PATCH V3 2/2] i2c designware add support of I2C standard mode
Date
From: Romain Baeriswyl <Romain.Baeriswyl@abilis.com>

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>
---
drivers/i2c/busses/i2c-designware-platdrv.c | 23 +++++++++++++++++++++--
1 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index fc24399..3685893 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -122,6 +122,7 @@ 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) {
@@ -151,6 +152,9 @@ static int dw_i2c_probe(struct platform_device *pdev)
return PTR_ERR(dev->clk);
clk_prepare_enable(dev->clk);

+ /* fast mode by default because of legacy reasons */
+ clk_freq = 400000;
+
if (pdev->dev.of_node) {
u32 ht = 0;
u32 ic_clk = dev->get_clk_rate_khz(dev);
@@ -166,6 +170,17 @@ 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);
+
+ /* Only standard mode at 100kHz and fast mode at 400kHz
+ * are supported.
+ */
+ if (clk_freq != 100000 && clk_freq != 400000) {
+ dev_err(&pdev->dev, "Only 100kHz and 400kHz supported");
+ return -EINVAL;
+ }
}

dev->functionality =
@@ -175,8 +190,12 @@ 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);
--
1.7.1


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