[PATCH] crypto: stm32/crc32 - Avoid lock if hardware is already used

[Nicolas Toromanoff]

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.toroman...@st.com>
---
 drivers/crypto/stm32/Kconfig       |  2 ++
 drivers/crypto/stm32/stm32-crc32.c | 15 ++++++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/stm32/Kconfig b/drivers/crypto/stm32/Kconfig
index 4ef3eb11361c..8d605b07571f 100644
--- a/drivers/crypto/stm32/Kconfig
+++ b/drivers/crypto/stm32/Kconfig
@@ -3,6 +3,8 @@ config CRYPTO_DEV_STM32_CRC
        tristate "Support for STM32 crc accelerators"
        depends on ARCH_STM32
        select CRYPTO_HASH
+       select CRYPTO_CRC32
+       select CRYPTO_CRC32C
        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);
 
-- 
2.17.1