[PATCH V2] crypto: qcom-rng - Add hw_random interface support

[Om Prakash Singh]

Add hw_random interface support in qcom-rng driver as new IP block
in Qualcomm SoC has inbuilt NIST SP800 90B compliant entropic source
to generate true random number.

Keeping current rng_alg interface as well for random number generation
using Kernel Crypto API.

Signed-off-by: Om Prakash Singh <quic_omprsing@xxxxxxxxxxx>
---

Changes in V2:
- Updated patch to fix the return value from qcom_rng_generate() to be
  consistent with current implementation
- Updated patch to make it more concise
- Removed unnecessary use local variable and it's initialization
- Updated patch to use devm_hwrng_register() instead of hwrng_register()
- Updated subject line of the patch

This patch is depends on [1]
[1] https://lore.kernel.org/lkml/20230824-topic-sm8550-rng-v2-4-dfcafbb16a3e@xxxxxxxxxx/

 drivers/crypto/qcom-rng.c | 65 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 58 insertions(+), 7 deletions(-)

diff --git a/drivers/crypto/qcom-rng.c b/drivers/crypto/qcom-rng.c
index fb54b8cfc35f..e5a574a3cc59 100644
--- a/drivers/crypto/qcom-rng.c
+++ b/drivers/crypto/qcom-rng.c
@@ -7,6 +7,7 @@
 #include <linux/acpi.h>
 #include <linux/clk.h>
 #include <linux/crypto.h>
+#include <linux/hw_random.h>
 #include <linux/io.h>
 #include <linux/iopoll.h>
 #include <linux/kernel.h>
@@ -32,13 +33,18 @@ struct qcom_rng {
 	struct mutex lock;
 	void __iomem *base;
 	struct clk *clk;
-	unsigned int skip_init;
+	struct qcom_rng_of_data *of_data;
 };
 
 struct qcom_rng_ctx {
 	struct qcom_rng *rng;
 };
 
+struct qcom_rng_of_data {
+	bool skip_init;
+	bool hwrng_support;
+};
+
 static struct qcom_rng *qcom_rng_dev;
 
 static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
@@ -70,7 +76,7 @@ static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
 		}
 	} while (currsize < max);
 
-	return 0;
+	return currsize;
 }
 
 static int qcom_rng_generate(struct crypto_rng *tfm,
@@ -92,6 +98,9 @@ static int qcom_rng_generate(struct crypto_rng *tfm,
 	mutex_unlock(&rng->lock);
 	clk_disable_unprepare(rng->clk);
 
+	if (ret == dlen)
+		ret = 0;
+
 	return ret;
 }
 
@@ -101,6 +110,13 @@ static int qcom_rng_seed(struct crypto_rng *tfm, const u8 *seed,
 	return 0;
 }
 
+static int qcom_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct qcom_rng *qrng = (struct qcom_rng *)rng->priv;
+
+	return qcom_rng_read(qrng, data, max);
+}
+
 static int qcom_rng_enable(struct qcom_rng *rng)
 {
 	u32 val;
@@ -136,7 +152,7 @@ static int qcom_rng_init(struct crypto_tfm *tfm)
 
 	ctx->rng = qcom_rng_dev;
 
-	if (!ctx->rng->skip_init)
+	if (!ctx->rng->of_data->skip_init)
 		return qcom_rng_enable(ctx->rng);
 
 	return 0;
@@ -157,6 +173,12 @@ static struct rng_alg qcom_rng_alg = {
 	}
 };
 
+static struct hwrng qcom_hwrng = {
+	.name = "qcom-hwrng",
+	.read = qcom_hwrng_read,
+	.quality = 1024,
+};
+
 static int qcom_rng_probe(struct platform_device *pdev)
 {
 	struct qcom_rng *rng;
@@ -177,15 +199,29 @@ static int qcom_rng_probe(struct platform_device *pdev)
 	if (IS_ERR(rng->clk))
 		return PTR_ERR(rng->clk);
 
-	rng->skip_init = (unsigned long)device_get_match_data(&pdev->dev);
+	rng->of_data = (struct qcom_rng_of_data *)of_device_get_match_data(&pdev->dev);
 
 	qcom_rng_dev = rng;
 	ret = crypto_register_rng(&qcom_rng_alg);
 	if (ret) {
 		dev_err(&pdev->dev, "Register crypto rng failed: %d\n", ret);
 		qcom_rng_dev = NULL;
+		return ret;
+	}
+
+	if (rng->of_data->hwrng_support) {
+		qcom_hwrng.priv = (unsigned long)qcom_rng_dev;
+		ret = devm_hwrng_register(&pdev->dev, &qcom_hwrng);
+		if (ret) {
+			dev_err(&pdev->dev, "Register hwrng failed: %d\n", ret);
+			qcom_rng_dev = NULL;
+			goto fail;
+		}
 	}
 
+	return ret;
+fail:
+	crypto_unregister_rng(&qcom_rng_alg);
 	return ret;
 }
 
@@ -198,6 +234,21 @@ static int qcom_rng_remove(struct platform_device *pdev)
 	return 0;
 }
 
+struct qcom_rng_of_data qcom_prng_of_data = {
+	.skip_init = false,
+	.hwrng_support = false,
+};
+
+struct qcom_rng_of_data qcom_prng_ee_of_data = {
+	.skip_init = true,
+	.hwrng_support = false,
+};
+
+struct qcom_rng_of_data qcom_trng_of_data = {
+	.skip_init = true,
+	.hwrng_support = true,
+};
+
 static const struct acpi_device_id __maybe_unused qcom_rng_acpi_match[] = {
 	{ .id = "QCOM8160", .driver_data = 1 },
 	{}
@@ -205,9 +256,9 @@ static const struct acpi_device_id __maybe_unused qcom_rng_acpi_match[] = {
 MODULE_DEVICE_TABLE(acpi, qcom_rng_acpi_match);
 
 static const struct of_device_id __maybe_unused qcom_rng_of_match[] = {
-	{ .compatible = "qcom,prng", .data = (void *)0},
-	{ .compatible = "qcom,prng-ee", .data = (void *)1},
-	{ .compatible = "qcom,trng", .data = (void *)1},
+	{ .compatible = "qcom,prng", .data = &qcom_prng_of_data },
+	{ .compatible = "qcom,prng-ee", .data = &qcom_prng_ee_of_data },
+	{ .compatible = "qcom,trng", .data = &qcom_trng_of_data },
 	{}
 };
 MODULE_DEVICE_TABLE(of, qcom_rng_of_match);
-- 
2.25.1