On Fri, Jun 7, 2013 at 3:08 AM, Dave Martin <Dave.Martin@xxxxxxx> wrote: >> I think we need to separate the concept of support for *a* secure >> monitor, from support for a *particular* secure monitor. > > There is no fixed set of functionality implemented by these interfaces, > so it might be better to think in terms of a generic "firmware" concept. > > > Come to think of it... > > One option could be to have some standard baseline firmware calling > conventions, so that we could have a few specific backends -- perhaps > this could be built on the "method" notion used by PSCI > > (see Documentation/devicetree/bindings/arm/psci.tst; this is probably > the most developed firmware interface binding we have today) > > There, method = "smc" means: > > populate registers in a certain way > SMC #0 > return results from register to caller in a certain way > > and method = "hvc" means: > > populate registers in a certain way > HVC #0 > return results from register to caller in a certain way > > > The backend method arch/arm/kernel/psci.c:__invoke_psci_fn_smc() > is probably close to what's needed for the tegra secureos case, > so in theory it could be common, along with some of the DT binding > conventions. > > The backends, and the convention for binding a firmware interface > to the appropriate backend, could then theoretically be handled > by a common framework. I'm not sure whether we could use the same backend for many different firmwares. If I understand you correctly, you propose to have a backend to the "smc" call that would cover the needs of all firmwares that rely on the smc instruction to invoke the firmware/secure monitor. I can understand the logic, but I'm not sure this is needed or even possible. For instance, the implementation you have in __invoke_psci_fn_smc assumes 4 arguments, while Tegra's only needs 3. Also (and although I have to confess I am not very knowledgeable about the "SecureOS" covered by this patch and need to double-check what follows), in Tegra's case registers r3-r11 can be altered by the secure monitor and need to be preserved - something you don't need to do with PSCI. Another example is the function that Tomasz shown (https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/arch/arm/mach-exynos/exynos-smc.S?id=refs/tags/next-20130606 ), which preserves r4-r11 but also assumes r3 is an argument - that's again another slightly different convention. All in all the needs of the various firmwares might end up being just different enough that we need to have a different backend for each of them. The firmware_ops defined in arch/arm/include/asm/firmware.h perform the abstraction at a higher level, which seems more fit here IMHO. Alex. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
