linux-kernel - [PATCH 1/2] nvmem: stm32: add warning when upper OTPs are updated

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Date:   Fri, 14 Oct 2022 17:04:28 +0200
From:   Patrick Delaunay <patrick.delaunay@...s.st.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>
CC:     Patrick Delaunay <patrick.delaunay@...s.st.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: [PATCH 1/2] nvmem: stm32: add warning when upper OTPs are updated

As the upper OTPs are ECC protected, they support only one 32 bits word
programming.
For a second modification of this word, these ECC become invalid and
this OTP will be no more accessible, the shadowed value is invalid.

This patch adds a warning to indicate an upper OTP update, because this
operation is dangerous as OTP is not locked by the driver after the first
update to avoid a second update.

Signed-off-by: Patrick Delaunay <patrick.delaunay@...s.st.com>
---

 drivers/nvmem/stm32-romem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/nvmem/stm32-romem.c b/drivers/nvmem/stm32-romem.c
index 354be526897f..e3c3c333b5d1 100644
--- a/drivers/nvmem/stm32-romem.c
+++ b/drivers/nvmem/stm32-romem.c
@@ -133,6 +133,9 @@ static int stm32_bsec_write(void *context, unsigned int offset, void *buf,
 		}
 	}
 
+	if (offset + bytes >= priv->lower * 4)
+		dev_warn(dev, "Update of upper OTPs with ECC protection (word programming, only once)\n");
+
 	return 0;
 }
 
-- 
2.25.1