| Message ID | 1369410236-22398-1-git-send-email-javi.merino@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, May 24, 2013 at 04:43:56PM +0100, Javi Merino wrote: > The Booting documentation assumes that the initial pagetables are > 16KiB but since 1b6ba46 (ARM: LPAE: MMU setup for the 3-level page > table format) they are 20KiB for LPAE kernels. Thus, the > recommendation to put atags or the dtb in the first 16KiB is wrong, > there's only 12KiB of space there in LPAE kernels, so update the > documentation accordingly. > --- > Documentation/arm/Booting | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) Missing Signed-off-by?
On Sun, May 26, 2013 at 01:27:52AM +0100, Rob Landley wrote: > On 05/24/2013 10:43:56 AM, Javi Merino wrote: > > The Booting documentation assumes that the initial pagetables are > > 16KiB but since 1b6ba46 (ARM: LPAE: MMU setup for the 3-level page > > table format) they are 20KiB for LPAE kernels. Thus, the > > recommendation to put atags or the dtb in the first 16KiB is wrong, > > there's only 12KiB of space there in LPAE kernels, so update the > > documentation accordingly. > > --- > > Documentation/arm/Booting | 9 +++++---- > > 1 file changed, 5 insertions(+), 4 deletions(-) > > Acked-by: Rob Landley <rob@landley.net> Thanks. As Catalin pointed out, I'm missing my SoB. > With one comment: > > > diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting > > index 0c1f475..f6f9cd8 100644 > > --- a/Documentation/arm/Booting > > +++ b/Documentation/arm/Booting > > @@ -105,7 +105,7 @@ The tagged list should be stored in system RAM. > > > > The tagged list must be placed in a region of memory where neither > > the kernel decompressor nor initrd 'bootp' program will overwrite > > -it. The recommended placement is in the first 16KiB of RAM. > > +it. The recommended placement is in the first 12KiB of RAM. > > > > 4b. Setup the device tree > > ------------------------- > > @@ -120,7 +120,7 @@ tagged list. > > The boot loader must pass at a minimum the size and location of the > > system memory, and the root filesystem location. The dtb must be > > placed in a region of memory where the kernel decompressor will not > > -overwrite it. The recommended placement is in the first 16KiB of RAM > > +overwrite it. The recommended placement is in the first 12KiB of RAM > > with the caveat that it may not be located at physical address 0 > > since > > the kernel interprets a value of 0 in r2 to mean neither a tagged > > list > > nor a dtb were passed. > > @@ -137,8 +137,9 @@ then it is legal for the boot loader to call the > > zImage in flash > > directly. > > > > The zImage may also be placed in system RAM (at any location) and > > -called there. Note that the kernel uses 16K of RAM below the image > > -to store page tables. The recommended placement is 32KiB into RAM. > > +called there. Note that the kernel may use up to 20KiB of RAM below > > +the image to store page tables. The recommended placement is 32KiB > > +into RAM. > > Now that we have three memory entires, possibly some sort of memory > layout would be in order? > > 0k-12k boot data (tagged list or device tree) > 12k-32k page tables > 32k-xxx kernel image > > Perhaps at the end of section 4's introduction? It's not quite obvious > from the document... Sounds like a good idea, I'll add it and send a v2. Cheers, Javi
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting index 0c1f475..f6f9cd8 100644 --- a/Documentation/arm/Booting +++ b/Documentation/arm/Booting @@ -105,7 +105,7 @@ The tagged list should be stored in system RAM. The tagged list must be placed in a region of memory where neither the kernel decompressor nor initrd 'bootp' program will overwrite -it. The recommended placement is in the first 16KiB of RAM. +it. The recommended placement is in the first 12KiB of RAM. 4b. Setup the device tree ------------------------- @@ -120,7 +120,7 @@ tagged list. The boot loader must pass at a minimum the size and location of the system memory, and the root filesystem location. The dtb must be placed in a region of memory where the kernel decompressor will not -overwrite it. The recommended placement is in the first 16KiB of RAM +overwrite it. The recommended placement is in the first 12KiB of RAM with the caveat that it may not be located at physical address 0 since the kernel interprets a value of 0 in r2 to mean neither a tagged list nor a dtb were passed. @@ -137,8 +137,9 @@ then it is legal for the boot loader to call the zImage in flash directly. The zImage may also be placed in system RAM (at any location) and -called there. Note that the kernel uses 16K of RAM below the image -to store page tables. The recommended placement is 32KiB into RAM. +called there. Note that the kernel may use up to 20KiB of RAM below +the image to store page tables. The recommended placement is 32KiB +into RAM. In either case, the following conditions must be met: