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Subject[PATCH v2] crypto: stm32/crc32 - Avoid lock if hardware is already used
Date
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>
---
v2: select CRC32 and not (CRYPTO_CRC32 and CRYPTO_CRC32C) in Kconfig
---
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 4ef3eb11361c..4a4c3284ae1f 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 783a64f3f635..75867c0b0017 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/io.h>
#include <linux/kernel.h>
@@ -149,7 +150,6 @@ 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)
@@ -157,7 +157,15 @@ 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
@@ -197,8 +205,9 @@ 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);

--
2.18.1
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