Linaro Connect is happening in San Francisco. They’ve got their presentations online, including a few firmware-related and security-related talks. I like the “Advanced Toolchain Usage” series.
http://www.linaro.org/blog/linaro-connect-2015-kicks-off-in-san-francisco/
http://www.linaro.org/blog/day-2-of-linaro-connect-sfo15/
https://www.linaro.org/blog/day-3-of-linaro-connect-sfo15/
https://www.linaro.org/blog/day-4-of-linaro-connect-sfo15/