Re: [PATCH v1] cache_v8: agilex5: Disable Dcache in the SPL

[Marc Zyngier <maz@kernel.org>]

On Mon, 26 Jun 2023 10:00:09 +0100,
"Lim, Jit Loon" <jit.loon.lim@intel.com> wrote:
> 
> 
> 
> > -----Original Message-----
> > From: Marek Vasut <marex@denx.de>
> > Sent: Wednesday, 21 June, 2023 10:20 PM
> > To: Marc Zyngier <maz@kernel.org>; Lim, Jit Loon <jit.loon.lim@intel.com>
> > Cc: u-boot@lists.denx.de; Jagan Teki <jagan@amarulasolutions.com>; Simon
> > <simon.k.r.goldschmidt@gmail.com>; Chee, Tien Fong
> > <tien.fong.chee@intel.com>; Hea, Kok Kiang <kok.kiang.hea@intel.com>;
> > Lokanathan, Raaj <raaj.lokanathan@intel.com>; Maniyam, Dinesh
> > <dinesh.maniyam@intel.com>; Ng, Boon Khai <boon.khai.ng@intel.com>;
> > Yuslaimi, Alif Zakuan <alif.zakuan.yuslaimi@intel.com>; Chong, Teik Heng
> > <teik.heng.chong@intel.com>; Zamri, Muhammad Hazim Izzat
> > <muhammad.hazim.izzat.zamri@intel.com>; Tang, Sieu Mun
> > <sieu.mun.tang@intel.com>; Ying-Chun Liu <paul.liu@linaro.org>; Lee, Kah
> > Jing <kah.jing.lee@intel.com>
> > Subject: Re: [PATCH v1] cache_v8: agilex5: Disable Dcache in the SPL
> > 
> > On 6/21/23 16:15, Marc Zyngier wrote:
> > > On Wed, 21 Jun 2023 15:06:51 +0100,
> > > Jit Loon Lim <jit.loon.lim@intel.com> wrote:
> > >>
> > >> From: Kah Jing Lee <kah.jing.lee@intel.com>
> > >>
> > >> Dcache feature is not enabled in SPL and enable it will cause ISR
> > >> exception. Since the Dcache is not supported in SPL, new
> > >> CONFIG_SPL_SYS_DISABLE_DCACHE_OPS is added to Kconfig to disable
> > >> Dcache in SPL.
> > >>
> > >> Signed-off-by: Kah Jing Lee <kah.jing.lee@intel.com>
> > >
> > > This is missing your own SoB.
> > >
> > > Now, I'd like to understand what you are actually trying to fix. What
> > > is this 'ISR' exception? This isn't something the architecture
> > > describes. Unless you are using CMOs on something that isn't memory or
> > > for which you don't have a mapping, this should never generate an
> > > exception.
> > 
> > You beat me to it, indeed, thanks !
> 
> The intention of doing this is because when we init SDMMC driver,
> the driver will call the invalidate_dcache_range.  However, during
> that time, the dcache is not available in SPL yet thus causing
> exception.

Again: which exception?

There is no such thing as "the dcache isn't available". It is always
valid to invalidate it, irrespective of it being enabled or not.

My impression is that you are papering over another bug (such as
feeding non-memory to the CMOs), and are getting an SError back, which
would be entirely justified.

	M.

-- 
Without deviation from the norm, progress is not possible.