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Diffstat (limited to 'doc/README.x86')
| -rw-r--r-- | doc/README.x86 | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/doc/README.x86 b/doc/README.x86 index 5f9c46f05d..d6b24ee75a 100644 --- a/doc/README.x86 +++ b/doc/README.x86 @@ -733,6 +733,30 @@ Example output: PCI_BDF(0, 3, 0) INTA PIRQA ... +Porting Hints +------------- + +Quark-specific considerations: + +To port U-Boot to other boards based on the Intel Quark SoC, a few things need +to be taken care of. The first important part is the Memory Reference Code (MRC) +parameters. Quark MRC supports memory-down configuration only. All these MRC +parameters are supplied via the board device tree. To get started, first copy +the MRC section of arch/x86/dts/galileo.dts to your board's device tree, then +change these values by consulting board manuals or your hardware vendor. +Available MRC parameter values are listed in include/dt-bindings/mrc/quark.h. +The other tricky part is with PCIe. Quark SoC integrates two PCIe root ports, +but by default they are held in reset after power on. In U-Boot, PCIe +initialization is properly handled as per Quark's firmware writer guide. +In your board support codes, you need provide two routines to aid PCIe +initialization, which are board_assert_perst() and board_deassert_perst(). +The two routines need implement a board-specific mechanism to assert/deassert +PCIe PERST# pin. Care must be taken that in those routines that any APIs that +may trigger PCI enumeration process are strictly forbidden, as any access to +PCIe root port's configuration registers will cause system hang while it is +held in reset. For more details, check how they are implemented by the Intel +Galileo board support codes in board/intel/galileo/galileo.c. + TODO List --------- - Audio |
