Re: [PATCH] devicetree: zynqmp.dtsi: Add bootmode selection support

From: Mike Looijmans
Date: Thu Feb 20 2020 - 03:01:19 EST

On 20-02-2020 08:01, Michal Simek wrote:
On 20. 02. 20 7:56, Mike Looijmans wrote:
On 19-02-2020 19:23, Vesa JÃÃskelÃinen wrote:
Hi Mike,

On 19.2.2020 14.20, Mike Looijmans wrote:
Add bootmode override support for ZynqMP devices. Allows one to select
a boot device by running "reboot qspi32" for example. Activate config
item CONFIG_SYSCON_REBOOT_MODE to make this work.

Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
 arch/arm64/boot/dts/xilinx/zynqmp.dtsi | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
index 26d926eb1431..4c38d77ecbba 100644
--- a/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
+++ b/arch/arm64/boot/dts/xilinx/zynqmp.dtsi
@@ -246,6 +246,30 @@
+ÂÂÂÂÂÂÂ /* Clock and Reset control registers for LPD */
+ÂÂÂÂÂÂÂ lpd_apb: apb@ff5e0000 {
+ÂÂÂÂÂÂÂÂÂÂÂ compatible = "syscon", "simple-mfd";
+ÂÂÂÂÂÂÂÂÂÂÂ reg = <0x0 0xff5e0000 0x0 0x400>;
+ÂÂÂÂÂÂÂÂÂÂÂ reboot-mode {
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ compatible = "syscon-reboot-mode";
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ offset = <0x200>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mask = <0xf100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /* Bit(8) is the "force user" bit */
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-normal = <0x0000>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-psjtag = <0x0100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-qspi24 = <0x1100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-qspi32 = <0x2100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-sd0ÂÂÂ = <0x3100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-nandÂÂ = <0x4100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-sd1ÂÂÂ = <0x6100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-emmcÂÂ = <0x6100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-usb0ÂÂ = <0x7100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-pjtag0 = <0x8100>;
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ mode-pjtag1 = <0x9100>;
+ mode-sd1ls = <0xe100>;

This kinda looks a bit misuse of reboot mode support.

Usually you are signal with reboot-mode that you want to do factory
reset, enter recovery mode or such things.

Now this signaling here is telling that this is used for selecting
from what device to boot from.

On the ZynqMP this is the only way to communicate with the ROM.

Another problem is that this now modifies all Xilinx Zynq MPSoCs which
is kinda wrong. This behavior should really be product/board specific
and not common for all boards -- undoing this in product/board is
somewhat cumbersome.

The boot mode setting is in the SOC, and is not board specific. The ROM
interprets this field. The only board specific thing is that you may not
actually have a NAND chip attached to it.

My idea was that a board could easily add say 'mode-recovery=<0x2100>;'
to make the QPSI boot the method of recovery. The bootloader also has
access to this register, so it can see that there was a boot mode
override in effect.

Now this change hijacks the "reboot <arg>" with this behavior which is
not so nice.

If anyone has a better suggestion as to where this should go, I'd be
more than happy to hear about it. It's the only interface that I could
find in the kernel to attach a bootmode override to.

IIRC as the part of PSCI 1.1 spec is SYSTEM_RESET2 where you can device
reset_type. IIRC that 0 as warm reset was coming based on discussion
with Xilinx (and maybe others) and I think this is what Xilinx is still
using. But didn't track it if that was really implemented or not.

I checked the arm-trusted-firmware code, there's no Xilinx vendor specific implementation of SYSTEM_RESET2 today, so it will only do a generic warm reboot and nothing else.

I'll move the patch to our BSP, we need the functionality for software update/recovery mechanisms.