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Date:   Thu, 27 Jan 2022 10:18:32 +0100
From:   Michael Walle <michael@walle.cc>
To:     Chen-Tsung Hsieh <chentsung@chromium.org>
Cc:     Tudor Ambarus <tudor.ambarus@microchip.com>,
        Pratyush Yadav <p.yadav@ti.com>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org
Subject: Re: [RESEND PATCH] mtd: spi-nor: core: Check written SR value in
 spi_nor_write_16bit_sr_and_check()
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References: <20220126073227.3401275-1-chentsung@chromium.org>
 <8625876c695685fc5409997403130194@walle.cc>
 <CAMu4cy5onQ2JNKhoLVmR4Nb7Cqv2L59SoE=2Q9CK8bhfPvvHTQ@mail.gmail.com>
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Am 2022-01-27 04:31, schrieb Chen-Tsung Hsieh:
> On Thu, Jan 27, 2022 at 6:38 AM Michael Walle <michael@walle.cc> wrote:
>> Out of curiosity, on what flash did you discover this?
> 
> It's Winbond W25Q64JWZPIM
> https://www.winbond.com/hq/product/code-storage-flash-memory/serial-nor-flash/?__locale=en&partNo=W25Q64JW
> 
> We are verifying the write protection on W25Q64JWZPIM and run into an
> issue that spi_nor_sr_unlock() always return success even if HW & SW
> write protection are both enabled.

Ah that ring a bell... Anyway, could you dump the SFDP data please?
See [1], you'll find the files in sysfs. I wonder why that flash is
using the 16bit write at all.

-michael

[1] 
https://lore.kernel.org/linux-mtd/4304e19f3399a0a6e856119d01ccabe0@walle.cc/