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First published at: https://forums.sifive.com/t/dont-fear-the-bricking-unbricking-unmatched-via-jtag/5449 Despite, as i think, this is quite obvious, some people miss the point. So let me show you how to unbrick the HiFive Unmatched board, that’s usefull in case of: installing BSP without the need of preparing the SD card in advance (you still have to insert it through) unbricking the board in case of deleting U-Boot testing U-Boot + OpenSBI on fly hijacking the load addresses The scheme works independently of selected MSEL value. ...

Intoduction This article is a logical continuation of the previous one and it is recommended to stady after reading the previous material. The current note is necessary for understanding the subsequent material, a further understanding gpio subsystem as a whole and helps with the development of own gpio drivers. The provisions of this article have not only apply to our virtual driver gpio, but also to any mmio gpio driver in general. It will focus on “optimizing” referred to in the preceding article. ...

Introduction It’s hard to underestimate the role of GPIO’s, especially in ARM embedded systems. Apart of being a very popular material for starters, GPIO’s provide a way for controlling the many peripheral devices, act as source of valuable interrupts, or even can be the only way to communicate the world for a SOC. ...