Re: [PATCH v3 2/3] i2c: designware: detect when dynamic tar update is possible

From: Jarkko Nikula
Date: Tue Aug 16 2016 - 10:00:19 EST


Hi, + Wolfram

On 07/29/2016 01:03 AM, Lucas De Marchi wrote:
This adapter can be synthesized with dynamic tar update enabled or disabled.
When enabled it is not necessary to disable the adapter to change the slave
address in some situations, which saves some time per transaction.

There is no direct register to know if this feature is enabled but we can do it
indirectly by writing to the 10BIT_ADDR field in IC_CON: this field is
read only when dynamic tar update is enabled.

Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Signed-off-by: Josà Roberto de Souza <jose.souza@xxxxxxxxx>
---
drivers/i2c/busses/i2c-designware-core.c | 37 ++++++++++++++++++++++----------
drivers/i2c/busses/i2c-designware-core.h | 1 +
2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 2c61585..a8408db 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -388,6 +388,20 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
/* configure the i2c master */
dw_writel(dev, dev->master_cfg , DW_IC_CON);

+ /*
+ * Test if dynamic TAR update is enabled in this controller by writing to

Over 80 characters in this line.

+ */
+ reg = dw_readl(dev, DW_IC_CON);
+ dw_writel(dev, reg ^ DW_IC_CON_10BITADDR_MASTER, DW_IC_CON);
+
+ if ((dw_readl(dev, DW_IC_CON) & DW_IC_CON_10BITADDR_MASTER) ==
+ (reg & DW_IC_CON_10BITADDR_MASTER)) {
+ dev->dynamic_tar_update_enabled = true;
+ dev_dbg(dev->dev, "Dynamic TAR update enabled");
+ }

Is this possible to move to i2c_dw_probe()? I guess the enabled status doesn't change runtime?

--
Jarkko