[PATCH 1/2] riscv: sbi: Remove sbi_spec_version

[Bin Meng]

Hi Rick,

On Tue, Jun 2, 2020 at 5:13 PM Rick Chen <rickchen36 at gmail.com> wrote:
>
> Hi Bin
>
> Bin Meng <bmeng.cn at gmail.com> 於 2020年6月1日 週一 下午5:06寫道：
> >
> > Hi Rick,
> >
> > On Mon, Jun 1, 2020 at 4:14 PM Rick Chen <rickchen36 at gmail.com> wrote:
> > >
> > > Hi Bin
> > >
> > > > From: Bin Meng [mailto:bmeng.cn at gmail.com]
> > > > Sent: Wednesday, May 27, 2020 5:05 PM
> > > > To: Rick Jian-Zhi Chen(陳建志); U-Boot Mailing List
> > > > Cc: Atish Patra; Bin Meng
> > > > Subject: [PATCH 1/2] riscv: sbi: Remove sbi_spec_version
> > > >
> > > > From: Bin Meng <bin.meng at windriver.com>
> > > >
> > > > U-Boot defaults to use SBI v0.2. Howerver there is a global variable sbi_spec_version that stills refers to v0.1. Since it is not used anywhere, let's remove it.
> > > >
> > > > Signed-off-by: Bin Meng <bin.meng at windriver.com>
> > > > ---
> > > >
> > > >  arch/riscv/include/asm/sbi.h | 2 --
> > > >  arch/riscv/lib/sbi.c         | 3 ---
> > > >  2 files changed, 5 deletions(-)
> > > >
> > > > diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h index 453cb5c..08e1ac0 100644
> > > > --- a/arch/riscv/include/asm/sbi.h
> > > > +++ b/arch/riscv/include/asm/sbi.h
> > > > @@ -77,7 +77,6 @@ enum sbi_ext_rfence_fid {
> > > >  #define SBI_FID_REMOTE_SFENCE_VMA_ASID SBI_EXT_RFENCE_REMOTE_SFENCE_VMA_ASID
> > > >  #endif
> > > >
> > > > -#define SBI_SPEC_VERSION_DEFAULT       0x1
> > > >  #define SBI_SPEC_VERSION_MAJOR_SHIFT   24
> > > >  #define SBI_SPEC_VERSION_MAJOR_MASK    0x7f
> > > >  #define SBI_SPEC_VERSION_MINOR_MASK    0xffffff
> > > > @@ -90,7 +89,6 @@ enum sbi_ext_rfence_fid {
> > > >  #define SBI_ERR_DENIED                 -4
> > > >  #define SBI_ERR_INVALID_ADDRESS                -5
> > > >
> > > > -extern unsigned long sbi_spec_version;
> > > >  struct sbiret {
> > > >         long error;
> > > >         long value;
> > > > diff --git a/arch/riscv/lib/sbi.c b/arch/riscv/lib/sbi.c index 993597e..f298846 100644
> > > > --- a/arch/riscv/lib/sbi.c
> > > > +++ b/arch/riscv/lib/sbi.c
> > > > @@ -11,9 +11,6 @@
> > > >  #include <asm/encoding.h>
> > > >  #include <asm/sbi.h>
> > > >
> > > > -/* default SBI version is 0.1 */
> > > > -unsigned long sbi_spec_version = SBI_SPEC_VERSION_DEFAULT;
> > >
> > > Why not keep this variable and get version of openSbi automatically,
> > > then register v01 or v02 callback function just like sbi_init() of
> > > Atish' patch.
> >
> > I feel this is not needed anyway, because we are using Kconfig option
> > to pass the same information.
>
> U-Boot proper has been configured as SBI_V02 by default currently.
> About backward compatible issue, it is not so friendly for users.
> They shall select SBI_VERSION configurations correctly in U-Boot
> proper and re-compile between different versions of openSbi.
> If U-Boot proper can probe openSbi and switch V01 or V02 mode
> automatically, users can run smoothly without awareness of SBI
> versions.
>

OpenSBI v0.7 is not backward compatible with previous version
regarding the multicore boot. Dynamically detecting SBI and the SBI
implementation version will make U-Boot codes very complicated. In
addition to SBI v0.1 vs. v0.2, we need detect whether SBI HSM
extension is available and if that's not available, U-Boot has to do
the lottery multi-core boot in every stage (SPL and proper). RISC-V is
a new architecture and without a lot of legacy burden to carry on, I
hope we can do the clean room implementation from the beginning.

Regards,
Bin