On 11/06/12 21:37, Linus Walleij wrote:
On Mon, Jun 11, 2012 at 5:25 PM, Lee Jones<lee.jones@xxxxxxxxxx> wrote:
As new users are
added, it is expected that they will be Device Tree compliant.
If this is the case, we will look up their initialisation values
by compatible entry, then apply them forthwith.
(...)
+static struct nmk_i2c_controller u8500_i2c = {
+ /*
+ * slave data setup time, which is
+ * 250 ns,100ns,10ns which is 14,6,2
+ * respectively for a 48 Mhz
+ * i2c clock
+ */
+ .slsu = 0xe,
+ /* Tx FIFO threshold */
+ .tft = 1,
+ /* Rx FIFO threshold */
+ .rft = 8,
+ /* std. mode operation */
+ .clk_freq = 100000,
+ /* Slave response timeout(ms) */
+ .timeout = 200,
+ .sm = I2C_FREQ_MODE_FAST,
+};
So why don't we create proper device tree bindings for the above platform
data?
For example several driver under
Documentation/devicetree/bindings/i2c/*
define the .clk_freq above as "clock-frequency"
samsung-i2c even has this:
samsung,i2c-sda-delay =<100>;
samsung,i2c-max-bus-freq =<100000>;
Where i2c-sda-delay corresponds to slsu above.
I suspect .sm can be derived from the frequency so it
is "FAST" whenever the frequency> 100000.
This looks to me like a way to push the burden of doing the real
device tree binding for the above to the next user.
(Which will likely be me, so therefore I care a bit ...)
On the contrary. This will avoid any added Device Tree complexity and
ensure that no extra vendor specific bindings are required. When a new
user wishes to use the driver, all they (you) have to do is create a new
struct with the platform specific information and add the entry to
nmk_gpio_match[], simples.
I've even added the logic to extract any information you provide via
nmk_gpio_match[] for use as platform data. This keeps it both out of
platform code and the Device Tree binary. Everyone's a winner. :)
--
Lee Jones
Linaro ST-Ericsson Landing Team Lead
M: +44 77 88 633 515
Linaro.org │ Open source software for ARM SoCs
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