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Date:   Fri, 3 Jun 2022 20:48:06 +0530
From:   Manivannan Sadhasivam <mani@kernel.org>
To:     Ansuel Smith <ansuelsmth@gmail.com>
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
Message-ID: <20220603151806.GB26696@thinkpad>
References: <20220519190112.6344-1-ansuelsmth@gmail.com>
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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

> 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
> 

-- 
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