Hello Stephen,
Am 01.08.2013 07:39, schrieb Stephen Warren:
On 07/31/2013 10:32 PM, Heiko Schocher wrote:
Hello Stephen,
Am 31.07.2013 21:31, schrieb Stephen Warren:
On 07/30/2013 11:46 PM, Heiko Schocher wrote:
...
Hmm.. each i2c adapter has its own init function ... why the tegra
driver do not use it? And do the necessary inits in it? So we
initialize an adapater only if we use it, which is also a rule
for u-boot ...
I have no hw, but it should be possible to add to process_nodes()
a parameter "controller_number" and call
process_nodes(controller_number, ...) from the i2c drivers init
function ...
There are two steps to initializing I2C on a Tegra system:
1) Parsing the DT to determine which/how-many I2C adapters exist in the
SoC. This will yield information such as the register address of the I2C
adapters, which clock/reset signal they rely on, perhaps the max bus
clock rate, etc.
This is a single global operation that needs to happen one single time
before anything else.
Why?
That's simply the way the code is written.
Ok.
This stage initializes the i2c_controllers[] array, since that's what
stores all the data parsed from DT.
2) Actually initializing or using the I2C HW. That could certainly be
part of the per-I2C-controller init() function you mention.
For that purpose is the i2c_init function.
And why we could not do step 1 when we do step 2? Why doing step 1
for hw we later do not use?
I suppose you could. It seems conceptually /far/ simpler to just scan
the DT once up-front rather than having to defer all this stuff until
on the other hand we ring for every ms boot time ... and here we want
to scan a complete dt with maybe a lot of nodes, we do not want to
use?
you actually use an I2C bus. If you do that, how can you know how many
I2C buses exist without trying to use every possible one and seeing
Do I really need to know that?
which fail? Also, the mapping from I2C bus number to register address is
Hmm.. there are max TEGRA_I2C_NUM_CONTROLLERS. If one gets used,
it scans the dt ... if only 1 adapter is used, only one is activated
through i2c_init ...
only created by actually scanning the whole DT; there's no need to every
I2C DT node to have a /aliases entry that dictates its U-Boot device ID,
so you really do have to scan everything completely up-front before you
can determine which registers to use.
But the i2c bus number is coded static all over the u-boot code (Should
be changed) in the code. Saying a board has an i2c eeprom on bus "2",
it calls i2c_set_bus_number(2) ... this "2" must be somewhere in the dt
or?
If this "2" is used on different boards with the same u-boot code only
different in dt, bus 2 maybe not exist ...
or if you change the order of i2c nodes in the dt "2" is no longer
"2" ... or?
saying something like this (just as an example, should be tested):
diff --git a/drivers/i2c/tegra_i2c.c b/drivers/i2c/tegra_i2c.c
index 9ac3969..7bbd3c7 100644
--- a/drivers/i2c/tegra_i2c.c
+++ b/drivers/i2c/tegra_i2c.c
@@ -378,81 +378,91 @@ static int i2c_get_config(const void *blob, int
node, struct i2c_bus *i2c_bus)
* @param is_scs 1 if this HW uses a single clock source (T114+)
* @return 0 if ok, -1 on error
*/
-static int process_nodes(const void *blob, int node_list[], int count,
+static int process_nodes(const void *blob, int node_list[],
+ struct i2c_adapter *adap, int count,
int is_dvc, int is_scs)
{
struct i2c_bus *i2c_bus;
- int i;
-
- /* build the i2c_controllers[] for each controller */
- for (i = 0; i< count; i++) {
- int node = node_list[i];
+ int node = node_list[i];
How do you determine i here? There's no guarantee that all I2C DT nodes
adap->hwadapnr
as in drivers/i2c/tegra_i2c.c:
static struct i2c_bus *tegra_i2c_get_bus(struct i2c_adapter *adap)
{
struct i2c_bus *bus;
bus = &i2c_controllers[adap->hwadapnr];
[...]
end up being processed in a single call to process_nodes(); there might
be some "Tegra20 I2C", some "Tegra20 I2C DVC", some "Tegra30 I2C"
modules in the same SoC.
bye,
Heiko
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