On Mon, Dec 28, 2020 at 7:05 PM Vitaly Wool [off-list ref] wrote:

On Mon, Dec 28, 2020 at 12:59 PM Anup Patel [off-list ref] wrote:

quoted

On Sat, Dec 26, 2020 at 10:03 PM Vitaly Wool [off-list ref] wrote:

quoted

Sometimes, especially in a production system we may not want to
use a "smart bootloader" like u-boot to load kernel, ramdisk and
device tree from a filesystem on eMMC, but rather load the kernel
from a NAND partition and just run it as soon as we can, and in
this case it is convenient to have device tree compiled into the
kernel binary. Since this case is not limited to MMU-less systems,
let's support it for these which have MMU enabled too.

Signed-off-by: Vitaly Wool <redacted>
---
 arch/riscv/Kconfig   |  1 -
 arch/riscv/mm/init.c | 12 ++++++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 2b41f6d8e458..9464b4e3a71a 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig

@@ -419,7 +419,6 @@ endmenu

 config BUILTIN_DTB
        def_bool n
-       depends on RISCV_M_MODE
        depends on OF

 menu "Power management options"

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 87c305c566ac..5d1c7a3ec01c 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c

@@ -194,12 +194,20 @@ void __init setup_bootmem(void)
        setup_initrd();
 #endif /* CONFIG_BLK_DEV_INITRD */

+       /*
+        * If DTB is built in, no need to reserve its memblock.
+        * OTOH, initial_boot_params has to be set to properly copy DTB
+        * before unflattening later on.
+        */
+       if (IS_ENABLED(CONFIG_BUILTIN_DTB))
+               initial_boot_params = __va(dtb_early_pa);

Don't assign initial_boot_params directly here because the
early_init_dt_scan() will do it.

early_init_dt_scan will set initial_boot_params to dtb_early_va from
the early mapping which will be gone by the time
unflatten_and_copy_device_tree() is called.

That's why we are doing early_init_dt_verify() again for the MMU-enabled
case which already takes care of your concern.

We use early_init_dt_verify() like most architectures to set the initial DTB.

quoted

The setup_vm() is supposed to setup dtb_early_va and dtb_early_pa
for MMU-enabled case so please add a "#ifdef" over there for the
built-in DTB case.

quoted

+       else
+               memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
+
        /*
         * Avoid using early_init_fdt_reserve_self() since __pa() does
         * not work for DTB pointers that are fixmap addresses
         */

This comment needs to be updated and moved along the memblock_reserve()
statement.

quoted

-       memblock_reserve(dtb_early_pa, fdt_totalsize(dtb_early_va));
-
        early_init_fdt_scan_reserved_mem();
        dma_contiguous_reserve(dma32_phys_limit);
        memblock_allow_resize();
--
2.29.2

This patch should be based upon Damiens builtin DTB patch.
Refer, https://www.spinics.net/lists/linux-gpio/msg56616.html

Thanks for the pointer, however I don't think our patches have
intersections. Besides, Damien is dealing with the MMU-less case
there.

Damien's patch is also trying to move to use generic BUILTIN_DTB
support for the MMU-less case so it is similar work hence the chance
of patch conflict.

Regards,
Anup