On Thu, Aug 16, 2012 at 22:27:42, Hunter, Jon wrote: > > On 08/15/2012 04:13 AM, Vaibhav Hiremath wrote: > > > > > > On 7/14/2012 3:56 AM, Jon Hunter wrote: > >> OMAP3 devices may or may not have security features enabled. Security enabled > >> devices are known as high-secure (HS) and devices without security are known as > >> general purpose (GP). > >> > >> For OMAP3 devices there are 12 general purpose timers available. On secure > >> devices the 12th timer is reserved for secure usage and so cannot be used by > >> the kernel, where as for a GP device it is available. We can detect the OMAP > >> device type, secure or GP, at runtime via an on-chip register. Today, when not > >> using DT, we do not register the 12th timer as a linux device if the device is > >> secure. > >> > >> When using device tree, device tree is going to register all the timer devices > >> it finds in the device tree blob. To prevent device tree from registering 12th > >> timer on a secure OMAP3 device we can add a status property to the timer > >> binding with the value "disabled" at boot time. Note that timer 12 on a OMAP3 > >> device has a property "ti,timer-secure" to indicate that it will not be > >> available on a secure device and so for secure OMAP3 devices, we search for > >> timers with this property and then disable them. Using the prom_add_property() > >> function to dynamically add a property was a recommended approach suggested by > >> Rob Herring [1]. > >> > >> I have tested this on an OMAP3 GP device and faking it to pretend to be a > >> secure device to ensure that any timers marked with "ti,timer-secure" are not > >> registered on boot. I have also made sure that all timers are registered as > >> expected on a GP device by default. > >> > >> [1] http://comments.gmane.org/gmane.linux.ports.arm.omap/79203 > >> > >> Signed-off-by: Jon Hunter <jon-hunter@xxxxxx> > >> --- > >> arch/arm/mach-omap2/board-generic.c | 1 + > >> arch/arm/mach-omap2/common.h | 1 + > >> arch/arm/mach-omap2/timer.c | 36 +++++++++++++++++++++++++++++++++++ > >> 3 files changed, 38 insertions(+) > >> > >> diff --git a/arch/arm/mach-omap2/board-generic.c b/arch/arm/mach-omap2/board-generic.c > >> index 6f93a20..20124d7 100644 > >> --- a/arch/arm/mach-omap2/board-generic.c > >> +++ b/arch/arm/mach-omap2/board-generic.c > >> @@ -40,6 +40,7 @@ static struct of_device_id omap_dt_match_table[] __initdata = { > >> static void __init omap_generic_init(void) > >> { > >> omap_sdrc_init(NULL, NULL); > >> + omap_dmtimer_init(); > >> > >> of_platform_populate(NULL, omap_dt_match_table, NULL, NULL); > >> } > >> diff --git a/arch/arm/mach-omap2/common.h b/arch/arm/mach-omap2/common.h > >> index 1f65b18..d6a4875 100644 > >> --- a/arch/arm/mach-omap2/common.h > >> +++ b/arch/arm/mach-omap2/common.h > >> @@ -326,6 +326,7 @@ extern void omap_sdrc_init(struct omap_sdrc_params *sdrc_cs0, > >> struct omap_sdrc_params *sdrc_cs1); > >> struct omap2_hsmmc_info; > >> extern int omap4_twl6030_hsmmc_init(struct omap2_hsmmc_info *controllers); > >> +extern void omap_dmtimer_init(void); > >> > >> #endif /* __ASSEMBLER__ */ > >> #endif /* __ARCH_ARM_MACH_OMAP2PLUS_COMMON_H */ > >> diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c > >> index 13d20c8..e3b9931 100644 > >> --- a/arch/arm/mach-omap2/timer.c > >> +++ b/arch/arm/mach-omap2/timer.c > >> @@ -36,6 +36,7 @@ > >> #include <linux/clocksource.h> > >> #include <linux/clockchips.h> > >> #include <linux/slab.h> > >> +#include <linux/of.h> > >> > >> #include <asm/mach/time.h> > >> #include <plat/dmtimer.h> > >> @@ -482,6 +483,41 @@ static int __init omap2_dm_timer_init(void) > >> } > >> arch_initcall(omap2_dm_timer_init); > >> > >> +static struct property timer_disabled = { > >> + .name = "status", > >> + .length = sizeof("disabled"), > >> + .value = "disabled", > >> +}; > >> + > >> +static struct of_device_id omap3_timer_match[] __initdata = { > >> + { .compatible = "ti,omap3-timer", }, > >> + { } > >> +}; > >> + > >> +/** > >> + * omap_dmtimer_init - initialisation function when device tree is used > >> + * > >> + * For secure OMAP3 devices, timers with device type "timer-secure" cannot > >> + * be used by the kernel as they are reserved. Therefore, to prevent the > >> + * kernel registering these devices remove them dynamically from the device > >> + * tree on boot. > >> + */ > >> +void __init omap_dmtimer_init(void) > >> +{ > >> + struct device_node *np; > >> + > >> + if (!cpu_is_omap34xx()) > >> + return; > >> + > > > > Sorry for responding so late, but why only omap34xx check here? > > Isn't this applicable to all omap & non-omap devices? > > It is only applicable to omap3 devices as far as omap is concerned. > > By non-omap, you are referring to the AMxxx stuff? > > Do AMxxx devices even support security (ie. secure boot and have secure > peripherals)? If not then this will work for AMxxx devices too. > Yes it does. AM33xx has 8 timers and Timer-0 is a secure timer. As in case of OMAP3, we do not even register timer-0 to kernel. > Let me know if the changelog is not clear why this is needed for an > omap3 device. > The changelog description is clear, but it is not only restricted to OMAP3. Thanks, Vaibhav -- 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
