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https://github.com/fail0verflow/switch-coreboot.git
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More information, we are on the next step, which is smbus support for
dram. Per the discussion on v3 list, I am self-acking this one. Signed-off-by: Ronald G. Minnich <rminnich@gmail.com> Acked-by: Ronald G. Minnich <rminnich@gmail.com> git-svn-id: svn://coreboot.org/repository/LinuxBIOSv3@340 f3766cd6-281f-0410-b1cd-43a5c92072e9
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Ronald G. Minnich
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@ -2077,6 +2077,8 @@ We pretty much get a ton of errors once include is fixed.
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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/home/rminnich/src/bios/LinuxBIOSv3/mainboard/amd/norwich/initram.c: In function
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'spd_read_byte': /home/rminnich/src/bios/LinuxBIOSv3/mainboard/amd/norwich/init
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ram.c:30: error: implicit declaration of function 'smbus_read_byte' /home/rminnic
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@ -2122,5 +2124,320 @@ Now what we have to do is start building initram in the familiar way, via
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\end_layout
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\begin_layout Paragraph
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Hold on.
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What are we doing here?
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\end_layout
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\begin_layout Standard
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We need to create an initram file for the LAR.
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This initram file is going to set up DRAM.
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LinuxBIOS supplies a skeleton function, which we show below, and the programmer
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needs to supply some functions for their chipsets, so that this function
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can work.
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\end_layout
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\begin_layout Standard
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What code is needed? A few things.
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The northbridge code must supply register set functions.
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The southbridge or superio must supply smbus read functions.
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The basic sdram setup is found in lib/ram.c, and is dead simple:
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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void ram_initialize(int controllers, void *ctrl) {
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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int i;
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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/* Set the registers we can set once to reasonable values.
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*/
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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for (i = 0; i < controllers; i++) {
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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printk(BIOS_INFO,
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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"Setting registers of RAM controller %d
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\backslash
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n", i);
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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ram_set_registers(ctrl, i);
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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}
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\end_layout
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\begin_layout LyX-Code
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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/* Now setup those things we can auto detect.
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*/
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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for (i = 0; i < controllers; i++) {
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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printk(BIOS_INFO,
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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"Setting SPD based registers of RAM controller %d
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\backslash
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n", i);
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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ram_set_spd_registers(ctrl, i);
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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}
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\end_layout
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\begin_layout LyX-Code
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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/* Now that everything is setup enable the RAM.
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Some chipsets do
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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* the work for us while on others we need to it by hand.
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*/
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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printk(BIOS_DEBUG, "Enabling RAM
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\backslash
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n");
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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ram_enable(controllers, ctrl);
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\end_layout
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\begin_layout LyX-Code
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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/* RAM initialization is done.
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*/
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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printk(BIOS_DEBUG, "RAM enabled successfully
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\backslash
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n");
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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}
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\end_layout
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\begin_layout Standard
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Ram_initialize is a core function of initram.
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When it is called, RAM is not working; after it is called, RAM is working.
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This function in turn calls functions in the northbridge code (or, in some
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cases, CPU code; it depends on the part).
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The basic idea is that this code is called with a pointer to an opaque
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type (ctlr *), and an int indicating how many controllers, dram slots,
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or whatever
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\begin_inset Quotes eld
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\end_inset
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things
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\begin_inset Quotes erd
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\end_inset
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there are, where a
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\begin_inset Quotes eld
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\end_inset
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thing
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\begin_inset Quotes erd
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\end_inset
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is totally chipset dependent.
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The lib/ram.c code sets hardcoded settings, then sets dynamic settings by
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querying the SPD bus, then enables the RAM.
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This basic cycle has been refined now for eight years and has worked well
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on many systems.
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\end_layout
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\begin_layout Standard
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The northbridge code has to provide three basic functions.
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The first function, ram_set_registers, sets up basic parameters.
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It will be called for each of the ram
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\begin_inset Quotes eld
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\end_inset
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things
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\begin_inset Quotes erd
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\end_inset
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, where, as described above,
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\begin_inset Quotes eld
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\end_inset
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thing
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\begin_inset Quotes erd
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\end_inset
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can be just about anything, depending on the chipset.
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The function will be called with the ctlr pointer, and in index in the
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range 0..controllers-1.
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The second function, ram_set_spd_registers, is called to tell the northbridge
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code that it should do spd setup for
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\begin_inset Quotes eld
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\end_inset
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thing
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\begin_inset Quotes erd
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\end_inset
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i.
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Finally, the northbridge-provided enable function is called.
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\end_layout
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\begin_layout Standard
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Any or all of these functions may be empty.
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In the common case, they all do something.
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These functions, in turn, may require other functions from other chipset
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parts.
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The most important, and common, set of functions reads SPD values using
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the SMBUS.
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The mainboard must configure, as part of stage2, a file to be compiled
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which provides these functions.
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The simplest function is called smbus_read_byte(unsigned device, unsigned
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address).
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This function should do any needed initialization, to keep life simple
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for the northbridge code, and then read from SMBUS device 'device' at address
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'address'.
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Typically, the device address range is 0xa0 up to 0xa8.
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The address depends on the DRAM technology.
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\end_layout
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\begin_layout Standard
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All of the LinuxBIOS code that is run after this point uses the device tree;
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none of the initram code uses the device tree.
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The reason is simple: the device tree lives in RAM.
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This bootstrap code is intentionally simple and does not use the device
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tree.
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\end_layout
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\begin_layout Standard
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We will start by providing SMBUS functions.
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The SMBUS for this board is supported on the AMD CS5536 chip.
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The file we create will be in southbridge/amd/cs5536/smbus_initram.c.
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\end_layout
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\begin_layout Standard
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The revision numbers skip a bit here, since others are also working on V3.
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We start with revision 339.
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\end_layout
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\begin_layout Subsubsection
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R339
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\end_layout
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\begin_layout Standard
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Get the old code:
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\end_layout
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\begin_layout LyX-Code
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cp LinuxBIOSv2/src/southbridge/amd/cs5536/cs5536_early_smbus.c southbridge/amd/cs
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5536/smbus_initram.c
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\end_layout
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\begin_layout Standard
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Then we need to set up the mainboard Makefile to include this file in the
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mainboard stage2.
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This is pretty easy: add the .o for this file to the INITRAM_OBJ in the
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mainboard Makefile:
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\end_layout
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\begin_layout LyX-Code
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\size tiny
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INITRAM_OBJ=$(obj)/stage0.init $(obj)/stage0.o $(obj)/mainboard/$(MAINBOARDDIR)/in
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itram.o $(obj)/southbridge/amd/cs5536/smbus_initram.o
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\end_layout
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\begin_layout Standard
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Now we get lots more errors, so off we go to fix them!
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\end_layout
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\begin_layout Standard
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\end_layout
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\end_body
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\end_document
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Loading…
Add table
Reference in a new issue