[U-Boot] [PATCH 6/6] riscv: ax25: use CCTL to flush d-cache

[Bin Meng]

Hi Rick,

On Wed, Jun 5, 2019 at 5:38 PM Rick Chen <rickchen36 at gmail.com> wrote:
>
> Hi Bin
>
> >
> > Hi Rick,
> >
> > On Tue, May 28, 2019 at 5:45 PM Andes <uboot at andestech.com> wrote:
> > >
> > > From: Rick Chen <rick at andestech.com>
> > >
> > > Use CCTL command to do d-cache write back and invalidate
> > > instead of fence.
> > >
> > > Signed-off-by: Rick Chen <rick at andestech.com>
> > > Cc: Greentime Hu <greentime at andestech.com>
> > > ---
> > >  arch/riscv/cpu/ax25/cache.c | 22 +++++++++++++---------
> > >  1 file changed, 13 insertions(+), 9 deletions(-)
> > >
> > > diff --git a/arch/riscv/cpu/ax25/cache.c b/arch/riscv/cpu/ax25/cache.c
> > > index 228fc55..d30071e 100644
> > > --- a/arch/riscv/cpu/ax25/cache.c
> > > +++ b/arch/riscv/cpu/ax25/cache.c
> > > @@ -5,17 +5,21 @@
> > >   */
> > >
> > >  #include <common.h>
> > > +#include <asm/csr.h>
> > > +
> > > +#ifdef CONFIG_RISCV_NDS_CACHE
> > > +/* mcctlcommand */
> > > +#define CCTL_REG_MCCTLCOMMAND_NUM      0x7cc
> > > +
> > > +/* D-cache operation */
> > > +#define CCTL_L1D_WBINVAL_ALL   6
> > > +#endif
> > >
> > >  void flush_dcache_all(void)
> > >  {
> > > -       /*
> > > -        * Andes' AX25 does not have a coherence agent. U-Boot must use data
> > > -        * cache flush and invalidate functions to keep data in the system
> > > -        * coherent.
> > > -        * The implementation of the fence instruction in the AX25 flushes the
> > > -        * data cache and is used for this purpose.
> > > -        */
> > > -       asm volatile ("fence" ::: "memory");
> > > +#ifdef CONFIG_RISCV_NDS_CACHE
> > > +       csr_write(CCTL_REG_MCCTLCOMMAND_NUM, CCTL_L1D_WBINVAL_ALL);
> >
> > I think CCTL_REG_MCCTLCOMMAND_NUM is a vendor specific CSR. Does
> > upstream GCC support this CSR?
>
> Yes. It is a vendor specific CSR. Upstream GCC shall not support it.
> So I isolate it by CONFIG_RISCV_NDS_CACHE.
>

OK, but I suspect you will need do something for the travis build
since upstream gcc is used?

Regards,
Bin