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

[Simon Glass]

Hi Bin,

On Tue, 23 Jun 2020 at 19:26, Bin Meng <bmeng.cn at gmail.com> wrote:
>
> Hi Simon,
>
> On Sun, Jun 21, 2020 at 9:10 PM Sagar Shrikant Kadam
> <sagar.kadam at sifive.com> wrote:
> >
> > 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;
>
> For this one, do you think we should fix the cpu_get_info() in
> cpu-uclass driver instead? With fix in the cpu-uclass driver we can
> avoid similar issue in any single CPU driver.

Yes it would be best to fix that function to zero the data.

Regards,
Simon