i2c: designware: Look for *CNT values in DT

The i2c-designware driver supports reading precise timing values from
ACPI, but the Device Tree support relies on a combination of standard
rise and fall times and hard-coded minimum timings. The result of this
is that it is difficult to get optimum timings, particularly given that
the values are bus speed-specific and only one set can be stored in
DT at a time.

Add support for initialisation from DT that is similar to that for
ACPI.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 855b698..47dfa13 100644 (file)
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -132,9 +132,18 @@ static int mscc_twi_set_sda_hold_time(struct dw_i2c_dev *dev)
        return 0;
 }
 
+static void dw_i2c_read_of_cnt(struct device_node *np, const char *name, u16 *pval)
+{
+       u32 val;
+
+       if (!of_property_read_u32(np, name, &val))
+               *pval = (u16)val;
+}
+
 static int dw_i2c_of_configure(struct platform_device *pdev)
 {
        struct dw_i2c_dev *dev = platform_get_drvdata(pdev);
+       struct device_node *np = pdev->dev.of_node;
 
        switch (dev->flags & MODEL_MASK) {
        case MODEL_MSCC_OCELOT:
@@ -146,6 +155,15 @@ static int dw_i2c_of_configure(struct platform_device *pdev)
                break;
        }
 
+       dw_i2c_read_of_cnt(np, "snps,ss_hcnt", &dev->ss_hcnt);
+       dw_i2c_read_of_cnt(np, "snps,ss_lcnt", &dev->ss_lcnt);
+       dw_i2c_read_of_cnt(np, "snps,fs_hcnt", &dev->fs_hcnt);
+       dw_i2c_read_of_cnt(np, "snps,fs_lcnt", &dev->fs_lcnt);
+       dw_i2c_read_of_cnt(np, "snps,fp_hcnt", &dev->fp_hcnt);
+       dw_i2c_read_of_cnt(np, "snps,fp_lcnt", &dev->fp_lcnt);
+       dw_i2c_read_of_cnt(np, "snps,hs_hcnt", &dev->hs_hcnt);
+       dw_i2c_read_of_cnt(np, "snps,hs_lcnt", &dev->hs_lcnt);
+
        return 0;
 }