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From: Evan Green <evgreen@chromium.org>
To: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Rob Herring <robh+dt@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Douglas Anderson <dianders@chromium.org>,
	Stephen Boyd <swboyd@chromium.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 3/3] nvmem: qfprom: Don't touch certain fuses
Date: Thu, 1 Oct 2020 14:49:26 -0700	[thread overview]
Message-ID: <CAE=gft4eDRBSuAQmiZQs3LegVyERWAJSmvmHKEY1N=z5HSViJQ@mail.gmail.com> (raw)
In-Reply-To: <d79de840-25cc-0e8e-15e6-3cc2fda2e38b@linaro.org>

On Thu, Oct 1, 2020 at 9:30 AM Srinivas Kandagatla
<srinivas.kandagatla@linaro.org> wrote:
>
>
>
> On 01/10/2020 17:27, Evan Green wrote:
> > On Thu, Oct 1, 2020 at 7:17 AM Srinivas Kandagatla
> > <srinivas.kandagatla@linaro.org> wrote:
> >>
> >> Hi Evan,
> >>
> >> On 29/09/2020 21:58, Evan Green wrote:
> >>> Some fuse ranges are protected by the XPU such that the AP cannot
> >>> access them. Attempting to do so causes an SError. Use the newly
> >>> introduced per-soc compatible string to attach the set of regions
> >>> we should not access. Then tiptoe around those regions.
> >>>
> >>
> >> This is a generic feature that can be used by any nvmem provider, can
> >> you move this logic to nvmem core instead of having it in qfprom!
> >
> > Sure! I'd prefer to keep this data in the driver for now rather than
> Ofcourse these can come from driver directly based on compatible!
>
> > trying to define DT bindings for the keepout zones. So then I'll pass
> > in my keepout array via struct nvmem_config at registration time, and
> > then the core can handle the keepout logic instead of qfprom.c.
> >
>
> Yes, that is inline with what am thinking of as well!

Oh no, I realized this isn't nearly as beautiful when I try to move it
into the core. The low level read/write interface between the nvmem
core and the driver is a range. So to move this into the core I'd have
to implement all the overlap computation logic to potentially break up
a read into several small reads in cases where there are many little
keepout ranges. It was much simpler when I could just check each byte
offset individually, and because I was doing it in this one
rarely-used driver I could make that performance tradeoff without much
penalty.

I could do all range/overlap handling if you want, but it'll be a
bigger change, and I worry my driver would be the only one to end up
using it. What do you think?
-Evan

>
>
> 00srini
> > -Evan
> >

  reply	other threads:[~2020-10-01 21:50 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-29 20:58 [PATCH 0/3] nvmem: qfprom: Avoid untouchable regions Evan Green
2020-09-29 20:58 ` [PATCH 1/3] dt-bindings: nvmem: Add qcom,sc7180-qfprom compatible string Evan Green
2020-10-02 22:20   ` Doug Anderson
2020-10-02 23:14     ` Evan Green
2020-10-05  9:15       ` Srinivas Kandagatla
2020-09-29 20:58 ` [PATCH 2/3] arm64: dts: qcom: sc7180: Add soc-specific qfprom compat string Evan Green
2020-10-02 22:24   ` Doug Anderson
2020-09-29 20:58 ` [PATCH 3/3] nvmem: qfprom: Don't touch certain fuses Evan Green
2020-10-01 14:17   ` Srinivas Kandagatla
2020-10-01 16:27     ` Evan Green
2020-10-01 16:30       ` Srinivas Kandagatla
2020-10-01 21:49         ` Evan Green [this message]
2020-10-05  9:12           ` Srinivas Kandagatla

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