Ohad Ben-Cohen <ohad@xxxxxxxxxx> writes: > On Wed, Oct 20, 2010 at 1:53 AM, Kevin Hilman > <khilman@xxxxxxxxxxxxxxxxxxx> wrote: >>> And to allow early board code to reserve specific hwspinlock numbers >>> for predefined use-cases, we probably want to be before arch_initcall. >> >> There's no reason for board code to have to do this at initcall time. > > If we want to have allow both allocations of predefined hwspinlocks > with omap_hwspinlock_request_specific(int), and dynamic allocations > (where we don't care about the specific instance of the hwspinlock we > will get) with omap_hwspinlock_request(), we must ensure that the > former _specific() API will never be called after the latter. > > If we will allow drivers to call omap_hwspinlock_request() before all > callers of omap_hwspinlock_request_specific() completed, then things > will break (because drivers might start getting hwspinlocks that are > predefined for dedicated use cases on the system). > > So if we want the _specific API to work, we can only allow early board > code to use it in order to reserve those predefined hwspinlocks before > drivers get the chance to call omap_hwspinlock_request(). > > The tempting alternative is not to provide the > omap_hwspinlock_request_specific() API at all (which is something we > discussed internally). > > Let's take the i2c-omap for example. > > It sounds like it must have a predefined hwspinlock, but what if: > > 1. It will use omap_hwspinlock_request() to dynamically allocate a hwspinlock > 2. Obviously, the hwspinlock id number must be communicated to the M3 > BIOS, so the i2c-omap will publish that id using a small shared memory > entry that will be allocated for this sole purpose > 3. we will make sure that 1+2 completes before the remote processor is > taken out of reset > > This does not require any smart IPC and it will allow us to get rid of > the omap_hwspinlock_request_specific() API and its early-callers > requirement. Yes, that would indeed simplify things. > All we will be left to take care of is the order of the ->probe() > execution (assuming we want both the i2c and the hwspinlock drivers to > be device_initcall) I understand the dependency between i2c and hwspinlock for some platforms with a shared i2c bus. Besides that being a broken hardware design, I can see the need for the i2c driver to take a hwspinlock for i2c xfers, but why does the i2c driver need to take the hwspinlock at probe time? Presumably, this is before the remote cores are executing code. >> >> This kind of thing needs to be done by platform_data function pointers, >> as is done for every other driver that needs platform-specific driver >> customization. > > Why would we need platform-specific function pointers here ? I'm not > sure I'm following this one. So that board code (built-in) does not call the hwspinlock driver (potentially a module.) The way to solve this is to have platform_data with function pointers, so that when the driver's ->probe() is done, it can call cany custom hooks registered by the board code. Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
