riscv: Rework riscv timer driver to only support S-mode

The riscv-timer driver currently serves as a shim for several riscv timer
drivers. This is not too desirable because it bypasses the usual timer
selection via the driver model. There is no easy way to specify an
alternate timing driver, or have the tick rate depend on the cpu's
configured frequency. The timer drivers also do not have device structs,
and so have to rely on storing parameters in gd_t. Lastly, there is no
initialization call, so driver init is done in the same function which
reads the time. This can result in confusing error messages. To a user, it
looks like the driver failed when trying to read the time, whereas it may
have failed while initializing.

This patch removes the shim functionality from the riscv-timer driver, and
has it instead implement the former rdtime.c timer driver. This is because
existing u-boot users who pass in a device tree (e.g. qemu) do not create a
timer device for S-mode u-boot. The existing behavior of creating the
riscv-timer device in the riscv cpu driver must be kept. The actual reading
of the CSRs has been redone in the style of Linux's get_cycles64.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Rick Chen <rick@andestech.com>

2 files changed, 0 insertions, 39 deletions

diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index 6c503ff2b2b..10ac5b06d3c 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -15,7 +15,6 @@ obj-$(CONFIG_SIFIVE_CLINT) += sifive_clint.o
 obj-$(CONFIG_ANDES_PLIC) += andes_plic.o
 obj-$(CONFIG_ANDES_PLMT) += andes_plmt.o
 else
-obj-$(CONFIG_RISCV_RDTIME) += rdtime.o
 obj-$(CONFIG_SBI) += sbi.o
 obj-$(CONFIG_SBI_IPI) += sbi_ipi.o
 endif
diff --git a/arch/riscv/lib/rdtime.c b/arch/riscv/lib/rdtime.c
deleted file mode 100644
index e128d7fce69..00000000000
--- a/arch/riscv/lib/rdtime.c
+++ /dev/null
@@ -1,38 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0+
-/*
- * Copyright (C) 2018, Anup Patel <anup@brainfault.org>
- * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
- *
- * The riscv_get_time() API implementation that is using the
- * standard rdtime instruction.
- */
-
-#include <common.h>
-
-/* Implement the API required by RISC-V timer driver */
-int riscv_get_time(u64 *time)
-{
-#ifdef CONFIG_64BIT
-	u64 n;
-
-	__asm__ __volatile__ (
-		"rdtime %0"
-		: "=r" (n));
-
-	*time = n;
-#else
-	u32 lo, hi, tmp;
-
-	__asm__ __volatile__ (
-		"1:\n"
-		"rdtimeh %0\n"
-		"rdtime %1\n"
-		"rdtimeh %2\n"
-		"bne %0, %2, 1b"
-		: "=&r" (hi), "=&r" (lo), "=&r" (tmp));
-
-	*time = ((u64)hi << 32) | lo;
-#endif
-
-	return 0;
-}