Anastasia Klimchuk has submitted this change. ( https://review.coreboot.org/c/flashrom/+/86312?usp=email )
Change subject: doc: Migrate doc about raspberry pi ......................................................................
doc: Migrate doc about raspberry pi
Old doc: https://wiki.flashrom.org/RaspberryPi
Change-Id: Ie3b7f2ed31f0b756815de055a2c58602263dac66 Signed-off-by: Anastasia Klimchuk aklm@flashrom.org Reviewed-on: https://review.coreboot.org/c/flashrom/+/86312 Tested-by: build bot (Jenkins) no-reply@coreboot.org Reviewed-by: Stefan Reinauer stefan.reinauer@coreboot.org --- M doc/user_docs/index.rst A doc/user_docs/raspberry_pi.rst 2 files changed, 57 insertions(+), 0 deletions(-)
Approvals: build bot (Jenkins): Verified Stefan Reinauer: Looks good to me, approved
diff --git a/doc/user_docs/index.rst b/doc/user_docs/index.rst index e03789e..7c56a28 100644 --- a/doc/user_docs/index.rst +++ b/doc/user_docs/index.rst @@ -12,6 +12,7 @@ misc_intel in_system msi_jspi1 + raspberry_pi misc_notes
.. Keep misc notes last diff --git a/doc/user_docs/raspberry_pi.rst b/doc/user_docs/raspberry_pi.rst new file mode 100644 index 0000000..db0e75f --- /dev/null +++ b/doc/user_docs/raspberry_pi.rst @@ -0,0 +1,56 @@ +=========== +RaspberryPi +=========== + +`RaspberryPi http://www.raspberrypi.org/faqs`_ is a cheap single-board computer developed in the UK +by the Raspberry Pi Foundation with the intention of stimulating the teaching of basic computer science in schools. +It can run a fully-functional GNU/Linux distribution and exposes SPI, I2C and several GPIOs on its expansion header. + +Prerequisites +============= + +Use latest Raspbian (or any other distribution with a recent kernel). +Run the following commands (or make sure these kernel modules are loaded successfully):: + + modprobe spi_bcm2835 # If that fails you may wanna try the older spi_bcm2708 module instead + modprobe spidev + +Connecting the flash chip +========================= + +To learn more about the RPi's expansion header refer to http://elinux.org/Rpi_Low-level_peripherals . +If you use one of the first A or B models, please make sure to not draw more than 50mA from the 3.3V pin. +Official numbers for newer models are hard to find but they use a switching regulator +that should provide a much higher margin. If the flash chip is still placed in a foreign circuit +(e.g. soldered to a PC mainboard) please refer to :doc:`/user_docs/in_system` for further details. + +========== ======================= +RPi header SPI flash +========== ======================= +25 GND +24 /CS +23 SCK +21 DO +19 DI +17 VCC 3.3V (+ /HOLD, /WP) +========== ======================= + +.. container:: danger, admonition + + Always connect all input pins of integrated circuits (not only flash chips). + +In general the other pins (usually pin 3 is /WP and pin 7 is /HOLD) should be connected to Vcc +unless they are required to be floating or connected to GND (both extremely uncommon for SPI flash chips). +Please consult the datasheet for the flash chip in question. + +If your flash chip is detected but your read/write/verify operations tend to fail, try to add decoupling capacitors (one 100nF and one 4.7uF ceramic capacitor is preferred) close to the flash chip's power pin. + +Running flashrom +================ + +Flashrom uses the Linux-native SPI driver, which is implemented by flashrom's linux_spi programmer. +To use the RaspberryPi with flashrom, you have to specify that programmer. You should always tell +it at what speed the SPI bus should run; you specify that with the spispeed parameter (given in kHz). +You also have to specify the Linux SPI device, e.g.:: + + flashrom -p linux_spi:dev=/dev/spidev0.0,spispeed=1000
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Anastasia Klimchuk (Code Review)