[PATCH v4 3/4] riscv: cpu: fixes to display proper CPU features

[Sagar Shrikant Kadam]

The cmd "cpu detail" fetches uninitialized cpu feature information
and thus displays wrong / inconsitent details as below. FU540-C000 doesn't
have any microcode, yet the cmd display's it.
=> cpu detail
  0: cpu at 0      rv64imac
        ID = 0, freq = 999.100 MHz: L1 cache, MMU, Microcode, Device ID
        Microcode version 0x0
        Device ID 0x0
  1: cpu at 1      rv64imafdc
        ID = 1, freq = 999.100 MHz: L1 cache, MMU, Microcode, Device ID
        Microcode version 0x0
        Device ID 0x0
  2: cpu at 2      rv64imafdc
        ID = 2, freq = 999.100 MHz: L1 cache, MMU, Microcode, Device ID
        Microcode version 0x0
        Device ID 0x0
  3: cpu at 3      rv64imafdc
        ID = 3, freq = 999.100 MHz: L1 cache, MMU, Microcode, Device ID
        Microcode version 0x0
        Device ID 0x0
  4: cpu at 4      rv64imafdc
        ID = 4, freq = 999.100 MHz: L1 cache, MMU, Microcode, Device ID
        Microcode version 0x0
        Device ID 0x0

The L1 cache or MMU entry seen above is also displayed inconsistently.
So initialize features to zero before fetching from device tree.
Additionally the conditional check to read "mmu-type" from device tree
is not rightly handled due to which the cpu feature doesn't include
CPU_FEAT_MMU even if it's corresponding entry is present in device tree.

We now see correct features as:

=> cpu detail
  0: cpu at 0      rv64imac
        ID = 0, freq = 999.100 MHz
  1: cpu at 1      rv64imafdc
        ID = 1, freq = 999.100 MHz: MMU
  2: cpu at 2      rv64imafdc
        ID = 2, freq = 999.100 MHz: MMU
  3: cpu at 3      rv64imafdc
        ID = 3, freq = 999.100 MHz: MMU
  4: cpu at 4      rv64imafdc
        ID = 4, freq = 999.100 MHz: MMU

Signed-off-by: Sagar Shrikant Kadam <sagar.kadam at sifive.com>
Reviewed-by: Pragnesh Patel <pragnesh.patel at sifive.com>
---
 drivers/cpu/riscv_cpu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/cpu/riscv_cpu.c b/drivers/cpu/riscv_cpu.c
index 76b0489..8c4b5e7 100644
--- a/drivers/cpu/riscv_cpu.c
+++ b/drivers/cpu/riscv_cpu.c
@@ -38,6 +38,8 @@ static int riscv_cpu_get_info(struct udevice *dev, struct cpu_info *info)
 
 	/* Zero out the frequency, in case sizeof(ulong) != sizeof(u32) */
 	info->cpu_freq = 0;
+	/* Initialise cpu features before updating from device tree */
+	info->features = 0;
 
 	/* First try getting the frequency from the assigned clock */
 	ret = clk_get_by_index(dev, 0, &clk);
@@ -52,7 +54,7 @@ static int riscv_cpu_get_info(struct udevice *dev, struct cpu_info *info)
 		dev_read_u32(dev, "clock-frequency", (u32 *)&info->cpu_freq);
 
 	mmu = dev_read_string(dev, "mmu-type");
-	if (!mmu)
+	if (mmu)
 		info->features |= BIT(CPU_FEAT_MMU);
 
 	return 0;
-- 
2.7.4