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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Nicolas Toromanoff <nicolas.toromanoff@st.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 133/633] crypto: stm32/crc32 - Avoid lock if hardware is already used
Date:   Tue, 27 Oct 2020 14:47:56 +0100
Message-Id: <20201027135528.927823983@linuxfoundation.org>
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From: Nicolas Toromanoff <nicolas.toromanoff@st.com>

[ Upstream commit bbf2cb1ea1e1428589d7f4d652bed15b265ce92d ]

If STM32 CRC device is already in use, calculate CRC by software.

This will release CPU constraint for a concurrent access to the
hardware, and avoid masking irqs during the whole block processing.

Fixes: 7795c0baf5ac ("crypto: stm32/crc32 - protect from concurrent accesses")

Signed-off-by: Nicolas Toromanoff <nicolas.toromanoff@st.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/crypto/stm32/Kconfig       |  1 +
 drivers/crypto/stm32/stm32-crc32.c | 15 ++++++++++++---
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/stm32/Kconfig b/drivers/crypto/stm32/Kconfig
index 4ef3eb11361c2..4a4c3284ae1f3 100644
--- a/drivers/crypto/stm32/Kconfig
+++ b/drivers/crypto/stm32/Kconfig
@@ -3,6 +3,7 @@ config CRYPTO_DEV_STM32_CRC
 	tristate "Support for STM32 crc accelerators"
 	depends on ARCH_STM32
 	select CRYPTO_HASH
+	select CRC32
 	help
 	  This enables support for the CRC32 hw accelerator which can be found
 	  on STMicroelectronics STM32 SOC.
diff --git a/drivers/crypto/stm32/stm32-crc32.c b/drivers/crypto/stm32/stm32-crc32.c
index 3ba41148c2a46..2c13f5214d2cf 100644
--- a/drivers/crypto/stm32/stm32-crc32.c
+++ b/drivers/crypto/stm32/stm32-crc32.c
@@ -6,6 +6,7 @@
 
 #include <linux/bitrev.h>
 #include <linux/clk.h>
+#include <linux/crc32.h>
 #include <linux/crc32poly.h>
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
@@ -147,7 +148,6 @@ static int burst_update(struct shash_desc *desc, const u8 *d8,
 	struct stm32_crc_desc_ctx *ctx = shash_desc_ctx(desc);
 	struct stm32_crc_ctx *mctx = crypto_shash_ctx(desc->tfm);
 	struct stm32_crc *crc;
-	unsigned long flags;
 
 	crc = stm32_crc_get_next_crc();
 	if (!crc)
@@ -155,7 +155,15 @@ static int burst_update(struct shash_desc *desc, const u8 *d8,
 
 	pm_runtime_get_sync(crc->dev);
 
-	spin_lock_irqsave(&crc->lock, flags);
+	if (!spin_trylock(&crc->lock)) {
+		/* Hardware is busy, calculate crc32 by software */
+		if (mctx->poly == CRC32_POLY_LE)
+			ctx->partial = crc32_le(ctx->partial, d8, length);
+		else
+			ctx->partial = __crc32c_le(ctx->partial, d8, length);
+
+		goto pm_out;
+	}
 
 	/*
 	 * Restore previously calculated CRC for this context as init value
@@ -195,8 +203,9 @@ static int burst_update(struct shash_desc *desc, const u8 *d8,
 	/* Store partial result */
 	ctx->partial = readl_relaxed(crc->regs + CRC_DR);
 
-	spin_unlock_irqrestore(&crc->lock, flags);
+	spin_unlock(&crc->lock);
 
+pm_out:
 	pm_runtime_mark_last_busy(crc->dev);
 	pm_runtime_put_autosuspend(crc->dev);
 
-- 
2.25.1