i2c-designware: make SDA hold time configurable

This patch makes the SDA hold time configurable through device tree.

Signed-off-by: Christian Ruppert <christian.ruppert@abilis.com>
Signed-off-by: Pierrick Hascoet <pierrick.hascoet@abilis.com>
Acked-by: Vineet Gupta <vgupta@synopsys.com> for arch/arc bits
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

3 files changed, 24 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 3de549436992..ad46616de29e 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -67,9 +67,12 @@
 #define DW_IC_STATUS            0x70
 #define DW_IC_TXFLR             0x74
 #define DW_IC_RXFLR             0x78
+#define DW_IC_SDA_HOLD          0x7c
 #define DW_IC_TX_ABRT_SOURCE    0x80
 #define DW_IC_ENABLE_STATUS     0x9c
 #define DW_IC_COMP_PARAM_1      0xf4
+#define DW_IC_COMP_VERSION      0xf8
+#define DW_IC_SDA_HOLD_MIN_VERS 0x3131312A
 #define DW_IC_COMP_TYPE         0xfc
 #define DW_IC_COMP_TYPE_VALUE   0x44570140
 
@@ -332,6 +335,16 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
         dw_writel(dev, lcnt, DW_IC_FS_SCL_LCNT);
         dev_dbg(dev->dev, "Fast-mode HCNT:LCNT = %d:%d\n", hcnt, lcnt);
 
+        /* Configure SDA Hold Time if required */
+        if (dev->sda_hold_time) {
+                reg = dw_readl(dev, DW_IC_COMP_VERSION);
+                if (reg >= DW_IC_SDA_HOLD_MIN_VERS)
+                        dw_writel(dev, dev->sda_hold_time, DW_IC_SDA_HOLD);
+                else
+                        dev_warn(dev->dev,
+                                "Hardware too old to adjust SDA hold time.");
+        }
+
         /* Configure Tx/Rx FIFO threshold levels */
         dw_writel(dev, dev->tx_fifo_depth - 1, DW_IC_TX_TL);
         dw_writel(dev, 0, DW_IC_RX_TL);
diff --git a/drivers/i2c/busses/i2c-designware-core.h b/drivers/i2c/busses/i2c-designware-core.h
index e761ad18dd61..912aa2262866 100644
--- a/drivers/i2c/busses/i2c-designware-core.h
+++ b/drivers/i2c/busses/i2c-designware-core.h
@@ -90,6 +90,7 @@ struct dw_i2c_dev {
         unsigned int            tx_fifo_depth;
         unsigned int            rx_fifo_depth;
         int                     rx_outstanding;
+        u32                     sda_hold_time;
 };
 
 #define ACCESS_SWAP             0x00000001
diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index ee46c92d7e3c..def79b5fd4c8 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -34,6 +34,7 @@
 #include <linux/sched.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
+#include <linux/of.h>
 #include <linux/of_i2c.h>
 #include <linux/platform_device.h>
 #include <linux/pm.h>
@@ -115,6 +116,15 @@ static int dw_i2c_probe(struct platform_device *pdev)
                 return PTR_ERR(dev->clk);
         clk_prepare_enable(dev->clk);
 
+        if (pdev->dev.of_node) {
+                u32 ht = 0;
+                u32 ic_clk = dev->get_clk_rate_khz(dev);
+
+                of_property_read_u32(pdev->dev.of_node,
+                                        "i2c-sda-hold-time-ns", &ht);
+                dev->sda_hold_time = ((u64)ic_clk * ht + 500000) / 1000000;
+        }
+
         dev->functionality =
                 I2C_FUNC_I2C |
                 I2C_FUNC_10BIT_ADDR |