linux-kernel - [PATCH v2 8/8] crypto: stm32/cryp

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Date:   Tue, 2 Nov 2021 17:47:29 +0100
From:   Nicolas Toromanoff <nicolas.toromanoff@...s.st.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>
CC:     Marek Vasut <marex@...x.de>,
        Nicolas Toromanoff <nicolas.toromanoff@...s.st.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        <linux-crypto@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2 8/8] crypto: stm32/cryp - reorder hw initialization

The CRYP IP checks the written key depending of the configuration, it's
safer to write the whole configuration to hardware then the key to avoid
unexpected key rejection.

Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@...s.st.com>
---
 drivers/crypto/stm32/stm32-cryp.c | 39 ++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/drivers/crypto/stm32/stm32-cryp.c b/drivers/crypto/stm32/stm32-cryp.c
index 5962fbb0bc91..d99eea9cb8cd 100644
--- a/drivers/crypto/stm32/stm32-cryp.c
+++ b/drivers/crypto/stm32/stm32-cryp.c
@@ -232,6 +232,11 @@ static inline int stm32_cryp_wait_busy(struct stm32_cryp *cryp)
 			!(status & SR_BUSY), 10, 100000);
 }
 
+static inline void stm32_cryp_enable(struct stm32_cryp *cryp)
+{
+	writel_relaxed(readl_relaxed(cryp->regs + CRYP_CR) | CR_CRYPEN, cryp->regs + CRYP_CR);
+}
+
 static inline int stm32_cryp_wait_enable(struct stm32_cryp *cryp)
 {
 	u32 status;
@@ -534,9 +539,6 @@ static int stm32_cryp_hw_init(struct stm32_cryp *cryp)
 	/* Disable interrupt */
 	stm32_cryp_write(cryp, CRYP_IMSCR, 0);
 
-	/* Set key */
-	stm32_cryp_hw_write_key(cryp);
-
 	/* Set configuration */
 	cfg = CR_DATA8 | CR_FFLUSH;
 
@@ -562,23 +564,36 @@ static int stm32_cryp_hw_init(struct stm32_cryp *cryp)
 	/* AES ECB/CBC decrypt: run key preparation first */
 	if (is_decrypt(cryp) &&
 	    ((hw_mode == CR_AES_ECB) || (hw_mode == CR_AES_CBC))) {
-		stm32_cryp_write(cryp, CRYP_CR, cfg | CR_AES_KP | CR_CRYPEN);
+		/* Configure in key preparation mode */
+		stm32_cryp_write(cryp, CRYP_CR, cfg | CR_AES_KP);
 
+		/* Set key only after full configuration done */
+		stm32_cryp_hw_write_key(cryp);
+
+		/* Start prepare key */
+		stm32_cryp_enable(cryp);
 		/* Wait for end of processing */
 		ret = stm32_cryp_wait_busy(cryp);
 		if (ret) {
 			dev_err(cryp->dev, "Timeout (key preparation)\n");
 			return ret;
 		}
-	}
 
-	cfg |= hw_mode;
+		cfg |= hw_mode | CR_DEC_NOT_ENC;
 
-	if (is_decrypt(cryp))
-		cfg |= CR_DEC_NOT_ENC;
+		/* Apply updated config (Decrypt + algo) and flush */
+		stm32_cryp_write(cryp, CRYP_CR, cfg);
+	} else {
+		cfg |= hw_mode;
+		if (is_decrypt(cryp))
+			cfg |= CR_DEC_NOT_ENC;
 
-	/* Apply config and flush (valid when CRYPEN = 0) */
-	stm32_cryp_write(cryp, CRYP_CR, cfg);
+		/* Apply config and flush */
+		stm32_cryp_write(cryp, CRYP_CR, cfg);
+
+		/* Set key only after configuration done */
+		stm32_cryp_hw_write_key(cryp);
+	}
 
 	switch (hw_mode) {
 	case CR_AES_GCM:
@@ -606,9 +621,7 @@ static int stm32_cryp_hw_init(struct stm32_cryp *cryp)
 	}
 
 	/* Enable now */
-	cfg |= CR_CRYPEN;
-
-	stm32_cryp_write(cryp, CRYP_CR, cfg);
+	stm32_cryp_enable(cryp);
 
 	return 0;
 }
-- 
2.17.1