[PATCH 2/5] arm: mvebu: Move internal registers in arch_very_early_init() function

[Pali Rohár]

On Friday 06 May 2022 14:04:53 Stefan Roese wrote:
> On 06.05.22 11:05, Pali Rohár wrote:
> > Moving of internal registers from INTREG_BASE_ADDR_REG to SOC_REGS_PHY_BASE
> > needs to be done very early, prior calling any function which may touch
> > internal registers, like debug_uart_init().
> > 
> > So do it earlier in arch_very_early_init() instead of arch_cpu_init().
> > 
> > Movement is done in proper U-Boot, not in SPL. SPL may return to bootrom
> > and bootrom requires internal registers at (old) expected location.
> > 
> > Signed-off-by: Pali Rohár <pali at kernel.org>
> > ---
> >   arch/arm/mach-mvebu/Kconfig    |  1 +
> >   arch/arm/mach-mvebu/Makefile   |  1 +
> >   arch/arm/mach-mvebu/cpu.c      | 31 -------------------------------
> >   arch/arm/mach-mvebu/lowlevel.S | 27 +++++++++++++++++++++++++++
> >   4 files changed, 29 insertions(+), 31 deletions(-)
> >   create mode 100644 arch/arm/mach-mvebu/lowlevel.S
> > 
> > diff --git a/arch/arm/mach-mvebu/Kconfig b/arch/arm/mach-mvebu/Kconfig
> > index a3f273f4f949..98b13d1e336d 100644
> > --- a/arch/arm/mach-mvebu/Kconfig
> > +++ b/arch/arm/mach-mvebu/Kconfig
> > @@ -16,6 +16,7 @@ config ARMADA_32BIT
> >   	select SUPPORT_SPL
> >   	select TRANSLATION_OFFSET
> >   	select SPL_SYS_NO_VECTOR_TABLE if SPL
> > +	select ARCH_VERY_EARLY_INIT
> >   config ARMADA_64BIT
> >   	bool
> > diff --git a/arch/arm/mach-mvebu/Makefile b/arch/arm/mach-mvebu/Makefile
> > index 1b451889d242..8bd2246325ca 100644
> > --- a/arch/arm/mach-mvebu/Makefile
> > +++ b/arch/arm/mach-mvebu/Makefile
> > @@ -21,6 +21,7 @@ else # CONFIG_ARCH_KIRKWOOD
> >   obj-y	= cpu.o
> >   obj-y	+= dram.o
> > +obj-y	+= lowlevel.o
> >   obj-$(CONFIG_DM_RESET) += system-controller.o
> >   ifndef CONFIG_SPL_BUILD
> >   obj-$(CONFIG_ARMADA_375) += ../../../drivers/ddr/marvell/axp/xor.o
> > diff --git a/arch/arm/mach-mvebu/cpu.c b/arch/arm/mach-mvebu/cpu.c
> > index 1e893777b292..173d95a760a3 100644
> > --- a/arch/arm/mach-mvebu/cpu.c
> > +++ b/arch/arm/mach-mvebu/cpu.c
> > @@ -413,20 +413,7 @@ static void update_sdram_window_sizes(void)
> >   	}
> >   }
> > -void mmu_disable(void)
> > -{
> > -	asm volatile(
> > -		"mrc p15, 0, r0, c1, c0, 0\n"
> > -		"bic r0, #1\n"
> > -		"mcr p15, 0, r0, c1, c0, 0\n");
> > -}
> > -
> >   #ifdef CONFIG_ARCH_CPU_INIT
> > -static void set_cbar(u32 addr)
> > -{
> > -	asm("mcr p15, 4, %0, c15, c0" : : "r" (addr));
> > -}
> > -
> >   #define MV_USB_PHY_BASE			(MVEBU_AXP_USB_BASE + 0x800)
> >   #define MV_USB_PHY_PLL_REG(reg)		(MV_USB_PHY_BASE | (((reg) & 0xF) << 2))
> >   #define MV_USB_X3_BASE(addr)		(MVEBU_AXP_USB_BASE | BIT(11) | \
> > @@ -476,24 +463,6 @@ int arch_cpu_init(void)
> >   	struct pl310_regs *const pl310 =
> >   		(struct pl310_regs *)CONFIG_SYS_PL310_BASE;
> > -	/*
> > -	 * Only with disabled MMU its possible to switch the base
> > -	 * register address on Armada 38x. Without this the SDRAM
> > -	 * located at >= 0x4000.0000 is also not accessible, as its
> > -	 * still locked to cache.
> > -	 */
> > -	mmu_disable();
> > -
> > -	/* Linux expects the internal registers to be at 0xf1000000 */
> > -	writel(SOC_REGS_PHY_BASE, INTREG_BASE_ADDR_REG);
> > -	set_cbar(SOC_REGS_PHY_BASE + 0xC000);
> > -
> > -	/*
> > -	 * From this stage on, the SoC detection is working. As we have
> > -	 * configured the internal register base to the value used
> > -	 * in the macros / defines in the U-Boot header (soc.h).
> > -	 */
> > -
> >   	if (mvebu_soc_family() == MVEBU_SOC_A38X) {
> >   		/*
> >   		 * To fully release / unlock this area from cache, we need
> > diff --git a/arch/arm/mach-mvebu/lowlevel.S b/arch/arm/mach-mvebu/lowlevel.S
> > new file mode 100644
> > index 000000000000..2491310eb0c1
> > --- /dev/null
> > +++ b/arch/arm/mach-mvebu/lowlevel.S
> > @@ -0,0 +1,27 @@
> > +/* SPDX-License-Identifier: GPL-2.0+ */
> > +
> > +#include <config.h>
> > +#include <linux/linkage.h>
> > +
> > +ENTRY(arch_very_early_init)
> > +#ifdef CONFIG_ARMADA_38X
> > +	/*
> > +	 * Only with disabled MMU its possible to switch the base
> > +	 * register address on Armada 38x. Without this the SDRAM
> > +	 * located at >= 0x4000.0000 is also not accessible, as its
> > +	 * still locked to cache.
> > +	 */
> > +	mrc	p15, 0, r0, c1, c0, 0
> > +	bic	r0, #1
> > +	mcr	p15, 0, r0, c1, c0, 0
> > +#endif
> 
> You are disabling the MMU here only for CONFIG_ARMADA_38X. In the
> non-asm version removed above, it's disabled in all cases in
> arch_cpu_init(). Is this correct? I might be missing something - it's
> been quite some time, since I worked on this code.

I'm not sure. I was in impression from that comment that disabling MMU
is needed only for A38x. But runtime detection of the board was not
possible until registers are relocated to the new location, so code
disabling MMU was called always.

So, this change should be tested on some AXP, A370 or A375 board to
verify that everything is working correctly.

I tested it only on A385 Turris Omnia.

> Thanks,
> Stefan
> 
> > +
> > +	/* Move internal registers from INTREG_BASE_ADDR_REG to SOC_REGS_PHY_BASE */
> > +	ldr	r0, =SOC_REGS_PHY_BASE
> > +	ldr	r1, =INTREG_BASE_ADDR_REG
> > +	str	r0, [r1]
> > +	add	r0, r0, #0xC000
> > +	mcr	p15, 4, r0, c15, c0
> > +
> > +	bx lr
> > +ENDPROC(arch_very_early_init)
> 
> Viele Grüße,
> Stefan Roese
> 
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