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[84.74.0.139]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48a4b329542sm352469085e9.3.2026.04.22.14.09.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Apr 2026 14:09:51 -0700 (PDT) From: Lothar Rubusch To: herbert@gondor.apana.org.au, thorsten.blum@linux.dev, davem@davemloft.net, nicolas.ferre@microchip.com, alexandre.belloni@bootlin.com, claudiu.beznea@tuxon.dev, ardb@kernel.org, linusw@kernel.org Cc: linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, l.rubusch@gmail.com Subject: [PATCH v3 3/3] crypto: atmel-sha204a - fix non-blocking read logic Date: Wed, 22 Apr 2026 21:09:36 +0000 Message-Id: <20260422210936.20095-4-l.rubusch@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260422210936.20095-1-l.rubusch@gmail.com> References: <20260422210936.20095-1-l.rubusch@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260422_140953_304640_C1BBDE7F X-CRM114-Status: GOOD ( 16.87 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The non-blocking path was (also) failing to provide valid entropy due to improper buffer management and a lack of hardware execution time. Ensure cmd.msecs (30ms) and cmd.rxsize (35ms) are initialized before enqueuing the background work. Fix the data offset to skip the 1-byte hardware count header when copying bits to the caller. Correctly return 0 (busy) to the hwrng core while hardware execution is in progress, preventing zero-filled buffers, which was the situation before. With this fix applied, tests will look similar to this: $ socat -u OPEN:/dev/hwrng,nonblock - | head -c 32 | hexdump -C 00000000 23 cc 42 3c 90 b1 38 fc 54 37 35 4b 09 c5 e1 0d |#.B<..8.T75K....| 2026/03/23 14:30:18 socat[858] E read(5, 0x55be363000, 8192): Resource temporarily unavailable 00000010 73 3b af d9 02 70 76 bd 2d 59 4b 12 01 ac ae 2b |s;...pv.-YK....+| 00000020 Fixes: da001fb651b0 ("crypto: atmel-i2c - add support for SHA204A random number generator") Signed-off-by: Lothar Rubusch --- drivers/crypto/atmel-sha204a.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/drivers/crypto/atmel-sha204a.c b/drivers/crypto/atmel-sha204a.c index f7dc00d0f4cd..04cbf80c1411 100644 --- a/drivers/crypto/atmel-sha204a.c +++ b/drivers/crypto/atmel-sha204a.c @@ -33,7 +33,6 @@ static void atmel_sha204a_rng_done(struct atmel_i2c_work_data *work_data, "i2c transaction failed (%d)\n", status); kfree(work_data); - rng->priv = 0; atomic_dec(&i2c_priv->tfm_count); return; } @@ -49,20 +48,19 @@ static int atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void *data, i2c_priv = container_of(rng, struct atmel_i2c_client_priv, hwrng); - /* Verify if data available from last run */ if (rng->priv) { work_data = (struct atmel_i2c_work_data *)rng->priv; - max = min(sizeof(work_data->cmd.data), max); - memcpy(data, &work_data->cmd.data, max); + max = min_t(size_t, ATMEL_RNG_BLOCK_SIZE, max); + memcpy(data, &work_data->cmd.data[1], max); - /* Now, free memory */ + /* Free memory and clear the in-flight flag */ kfree(work_data); rng->priv = 0; atomic_dec(&i2c_priv->tfm_count); return max; } - /* When a request is still in-flight but not processed */ + /* If a request is still in-flight, return 0 (busy) */ if (atomic_read(&i2c_priv->tfm_count) > 0) return 0; @@ -76,8 +74,14 @@ static int atmel_sha204a_rng_read_nonblocking(struct hwrng *rng, void *data, work_data->client = i2c_priv->client; atmel_i2c_init_random_cmd(&work_data->cmd); + + /* Set the execution time for the RNG command (from datasheet) */ + work_data->cmd.msecs = ATMEL_RNG_EXEC_TIME; + work_data->cmd.rxsize = RANDOM_RSP_SIZE; + atmel_i2c_enqueue(work_data, atmel_sha204a_rng_done, rng); + /* Return 0 to indicate 'busy', data will be ready on next call */ return 0; } -- 2.53.0