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Date:   Fri, 3 Jun 2022 17:25:56 +0200
From:   Ansuel Smith <ansuelsmth@gmail.com>
To:     Manivannan Sadhasivam <mani@kernel.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        linux-mtd@lists.infradead.org, linux-arm-msm@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 0/2] Add support for unprotected spare data page
References: <20220519190112.6344-1-ansuelsmth@gmail.com>
 <20220603151806.GB26696@thinkpad>
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On Fri, Jun 03, 2022 at 08:48:06PM +0530, Manivannan Sadhasivam wrote:
> On Thu, May 19, 2022 at 09:01:10PM +0200, Ansuel Smith wrote:
> > Some background about this.
> > On original qsdk ipq8064 based firmware there was a big separation from
> > boot partition and user partition. With boot partition we refer to
> > partition used to init the router (bootloader, spm firmware and other
> > internal stuff) With user partition we refer to linux partition and data
> > partition not used to init the router.
> > When someone had to write to these boot partition a special mode was
> > needed, to switch the nand driver to this special configuration.
> > 
> > Upstream version of the nandc driver totally dropped this and the result
> > is that if someone try to read data from these partition a CRC warning
> > is printed and if someone try to write that (if for example someone
> > wants to replace the bootloader) result is a broken system as the data
> > is badly written.
> > 
> 
> Can you please point me to the downstream/vendor driver that has this
> implementation?
> 
> Thanks,
> Mani
>

Actually found the repo...This is the link [1].

My implementation is a variant of this since originally they used a
sysfs entry to swap the ecc configuration.

[1] https://github.com/marxfang/ipq807x-spf100-cs/blob/master/qsdk/qca/src/linux-4.4/drivers/mtd/nand/qcom_nandc.c

> > This series comes to fix this.
> > 
> > A user can declare offset and size of these special partition using the
> > qcom,boot-pages binding.
> > 
> > An initial implementation of this assumed that the boot-pages started
> > from the start of the nand but we discover that some device have backup
> > of these special partition and we can have situation where we have this
> > partition scheme
> > - APPSBL (require special mode)
> > - APPSBLENV (doesn't require special mode)
> > - ART
> > - APPSBLBK (back of APPSBL require special mode)
> > - APPSBLENVBK (back of APPSBLENV doesn't require special mode)
> > With this configuration we need to declare sparse boot page and we can't
> > assume boot-pages always starts from the start of the nand.
> > 
> > A user can use this form to declare sparse boot pages
> > qcom,boot-pages = <0x0 0x0c80000 0x0c80000 0x0500000>;
> > 
> > The driver internally will parse this array, convert it to nand pages
> > and check internally on every read/write if this special configuration
> > should used for that page or the normal one.
> > 
> > The reason for all of this is that qcom FOR SOME REASON, disable ECC for
> > spare data only for these boot partition and we need to reflect this
> > special configuration to mute these warning and to permit actually
> > writing to these pages.
> > 
> > v4:
> > - Fix wrong compatible set for boot-pages (ipq8074 instead of ipq806x)
> > v3:
> > - Fix typo in Docmunetation commit desription
> > - Add items description for uint32-matrix
> > v2:
> > - Add fixes from Krzysztof in Documentation
> > 
> > Ansuel Smith (2):
> >   mtd: nand: raw: qcom_nandc: add support for unprotected spare data
> >     pages
> >   dt-bindings: mtd: qcom_nandc: document qcom,boot-pages binding
> > 
> >  .../devicetree/bindings/mtd/qcom,nandc.yaml   |  26 +++
> >  drivers/mtd/nand/raw/qcom_nandc.c             | 148 +++++++++++++++++-
> >  2 files changed, 169 insertions(+), 5 deletions(-)
> > 
> > -- 
> > 2.34.1
> > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்

-- 
	Ansuel