[PATCH] riscv: Split SiFive CLINT support between SPL and U-Boot proper

[Sean Anderson]

On 5/11/21 8:04 AM, Bin Meng wrote:
> At present there is only one Kconfig option CONFIG_SIFIVE_CLINT to
> control the enabling of SiFive CLINT support in both SPL (M-mode)
> and U-Boot proper (S-mode). So for a typical SPL config that the
> SiFive CLINT driver is enabled in both SPL and U-Boot proper, that
> means the S-mode U-Boot tries to access the memory-mapped CLINT
> registers directly, instead of the normal 'rdtime' instruction.
> 
> This was not a problem before, as the hardware does not forbid the
> access from S-mode. However this becomes an issue now with OpenSBI
> commit 8b569803475e ("lib: utils/sys: Add CLINT memregion in the root domain")
> that the SiFive CLINT register space is protected by PMP for M-mode
> access only. U-Boot proper does not boot any more with the latest
> OpenSBI, that access exceptions are fired forever from U-Boot when
> trying to read the timer value via the SiFive CLINT driver in U-Boot.
> 
> To solve this, we need to split current SiFive CLINT support between
> SPL and U-Boot proper, using 2 separate Kconfig options.
> 
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
> ---
> 
>   arch/riscv/Kconfig                   | 9 ++++++++-
>   arch/riscv/cpu/fu540/Kconfig         | 2 +-
>   arch/riscv/cpu/generic/Kconfig       | 3 ++-
>   arch/riscv/include/asm/global_data.h | 2 +-
>   arch/riscv/lib/Makefile              | 2 +-
>   drivers/timer/Makefile               | 2 +-
>   6 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 3f221dccdb..82e10da11e 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -158,7 +158,14 @@ config DMA_ADDR_T_64BIT
>   
>   config SIFIVE_CLINT
>   	bool
> -	depends on RISCV_MMODE || SPL_RISCV_MMODE
> +	depends on RISCV_MMODE
> +	help
> +	  The SiFive CLINT block holds memory-mapped control and status registers
> +	  associated with software and timer interrupts.
> +
> +config SPL_SIFIVE_CLINT
> +	bool
> +	depends on SPL_RISCV_MMODE
>   	help
>   	  The SiFive CLINT block holds memory-mapped control and status registers
>   	  associated with software and timer interrupts.
> diff --git a/arch/riscv/cpu/fu540/Kconfig b/arch/riscv/cpu/fu540/Kconfig
> index 616b25650f..dcf099447b 100644
> --- a/arch/riscv/cpu/fu540/Kconfig
> +++ b/arch/riscv/cpu/fu540/Kconfig
> @@ -11,7 +11,7 @@ config SIFIVE_FU540
>   	imply CPU
>   	imply CPU_RISCV
>   	imply RISCV_TIMER if (RISCV_SMODE || SPL_RISCV_SMODE)
> -	imply SIFIVE_CLINT if (RISCV_MMODE || SPL_RISCV_MMODE)
> +	imply SPL_SIFIVE_CLINT
>   	imply CMD_CPU
>   	imply SPL_CPU
>   	imply SPL_OPENSBI
> diff --git a/arch/riscv/cpu/generic/Kconfig b/arch/riscv/cpu/generic/Kconfig
> index a4934bb957..e025134b23 100644
> --- a/arch/riscv/cpu/generic/Kconfig
> +++ b/arch/riscv/cpu/generic/Kconfig
> @@ -9,7 +9,8 @@ config GENERIC_RISCV
>   	imply CPU
>   	imply CPU_RISCV
>   	imply RISCV_TIMER if (RISCV_SMODE || SPL_RISCV_SMODE)
> -	imply SIFIVE_CLINT if (RISCV_MMODE || SPL_RISCV_MMODE)
> +	imply SIFIVE_CLINT if RISCV_MMODE
> +	imply SPL_SIFIVE_CLINT if SPL_RISCV_MMODE
>   	imply CMD_CPU
>   	imply SPL_CPU
>   	imply SPL_OPENSBI
> diff --git a/arch/riscv/include/asm/global_data.h b/arch/riscv/include/asm/global_data.h
> index d3a0b1d221..095484a635 100644
> --- a/arch/riscv/include/asm/global_data.h
> +++ b/arch/riscv/include/asm/global_data.h
> @@ -18,7 +18,7 @@
>   struct arch_global_data {
>   	long boot_hart;		/* boot hart id */
>   	phys_addr_t firmware_fdt_addr;
> -#ifdef CONFIG_SIFIVE_CLINT
> +#if CONFIG_IS_ENABLED(SIFIVE_CLINT)
>   	void __iomem *clint;	/* clint base address */
>   #endif
>   #ifdef CONFIG_ANDES_PLIC
> diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
> index d08cbe9b79..c4cc41434b 100644
> --- a/arch/riscv/lib/Makefile
> +++ b/arch/riscv/lib/Makefile
> @@ -11,7 +11,7 @@ obj-$(CONFIG_CMD_BOOTI) += bootm.o image.o
>   obj-$(CONFIG_CMD_GO) += boot.o
>   obj-y	+= cache.o
>   ifeq ($(CONFIG_$(SPL_)RISCV_MMODE),y)
> -obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint.o
> +obj-$(CONFIG_$(SPL_)SIFIVE_CLINT) += sifive_clint.o
>   obj-$(CONFIG_ANDES_PLIC) += andes_plic.o
>   else
>   obj-$(CONFIG_SBI) += sbi.o
> diff --git a/drivers/timer/Makefile b/drivers/timer/Makefile
> index eb5c48cc6c..2ebdeab0ce 100644
> --- a/drivers/timer/Makefile
> +++ b/drivers/timer/Makefile
> @@ -19,7 +19,7 @@ obj-$(CONFIG_RENESAS_OSTM_TIMER) += ostm_timer.o
>   obj-$(CONFIG_RISCV_TIMER) += riscv_timer.o
>   obj-$(CONFIG_ROCKCHIP_TIMER) += rockchip_timer.o
>   obj-$(CONFIG_SANDBOX_TIMER)	+= sandbox_timer.o
> -obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint_timer.o
> +obj-$(CONFIG_$(SPL_)SIFIVE_CLINT) += sifive_clint_timer.o
>   obj-$(CONFIG_STI_TIMER)		+= sti-timer.o
>   obj-$(CONFIG_STM32_TIMER)	+= stm32_timer.o
>   obj-$(CONFIG_X86_TSC_TIMER)	+= tsc_timer.o
> 

Reviewed-by: Sean Anderson <seanga2 at gmail.com>