[PATCH V5] i2c: designware: fix wrong Tx/Rx FIFO for ACPI

Tin Huynh
2016-12-14T09:24:15Z

ACPI always sets Tx/Rx FIFO to 32. This configuration will
cause problem if the IP core supports a FIFO size of less than 32.
The driver should read the FIFO size from the IP and select the smaller
one of the two.

Signed-off-by: Tin Huynh <tnhuynh@apm.com>

---
drivers/i2c/busses/i2c-designware-platdrv.c | 31 ++++++++++++++++++++------
1 files changed, 24 insertions(+), 7 deletions(-)

Change from V4:
-Change else condition and add some comments to clarify new approach.

Change from V3:
-Use uppercase of FIFO instead of lowercase.
-Correct else condition when IP core return 0 of FIFO.

Change from V2:
-Add a helper function to set FIFO size.

Change from V1:
-Revert the default 32 for FIFO, read parameter from IP core
and pick the smaller one of the two.
-Correct the title to describe new approach.

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index 0b42a12..682adc3 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -150,6 +150,29 @@ static int i2c_dw_plat_prepare_clk(struct dw_i2c_dev *i_dev, bool prepare)
return 0;
}

+static void dw_i2c_set_fifo_size(struct dw_i2c_dev *dev, int id)
+{
+ u32 param, tx_fifo_depth, rx_fifo_depth;
+
+ /*
+ * Try to detect the FIFO depth if not set by interface driver,
+ * the depth could be from 2 to 256 from HW spec.
+ */
+ param = i2c_dw_read_comp_param(dev);
+ tx_fifo_depth = ((param >> 16) & 0xff) + 1;
+ rx_fifo_depth = ((param >> 8) & 0xff) + 1;
+ if (!dev->tx_fifo_depth) {
+ dev->tx_fifo_depth = tx_fifo_depth;
+ dev->rx_fifo_depth = rx_fifo_depth;
+ dev->adapter.nr = id;
+ } else if (tx_fifo_depth >= 2) {
+ dev->tx_fifo_depth = min_t(u32, dev->tx_fifo_depth,
+ tx_fifo_depth);
+ dev->rx_fifo_depth = min_t(u32, dev->rx_fifo_depth,
+ rx_fifo_depth);
+ }
+}
+
static int dw_i2c_plat_probe(struct platform_device *pdev)
{
struct dw_i2c_platform_data *pdata = dev_get_platdata(&pdev->dev);
@@ -246,13 +269,7 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
1000000);
}

- if (!dev->tx_fifo_depth) {
- u32 param1 = i2c_dw_read_comp_param(dev);
-
- dev->tx_fifo_depth = ((param1 >> 16) & 0xff) + 1;
- dev->rx_fifo_depth = ((param1 >> 8) & 0xff) + 1;
- dev->adapter.nr = pdev->id;
- }
+ dw_i2c_set_fifo_size(dev, pdev->id);

adap = &dev->adapter;
adap->owner = THIS_MODULE;
--
1.7.1