[PATCH] crypto: qcom-rng: Add hwrng support

[Om Prakash Singh <quic_omprsing@quicinc.com>]

This is follow patch on top of [1] to add hwrng support for newer
platform with trng capability.

[1] https://lore.kernel.org/lkml/20230824-topic-sm8550-rng-v2-4-dfcafbb16a3e@linaro.org/

Signed-off-by: Om Prakash Singh <quic_omprsing@quicinc.com>
---
 drivers/crypto/qcom-rng.c | 72 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 63 insertions(+), 9 deletions(-)

diff --git a/drivers/crypto/qcom-rng.c b/drivers/crypto/qcom-rng.c
index fb54b8cfc35f..f78ffdcc66ec 100644
--- a/drivers/crypto/qcom-rng.c
+++ b/drivers/crypto/qcom-rng.c
@@ -13,6 +13,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
+#include <linux/hw_random.h>
 
 /* Device specific register offsets */
 #define PRNG_DATA_OUT		0x0000
@@ -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,
@@ -79,7 +85,8 @@ static int qcom_rng_generate(struct crypto_rng *tfm,
 {
 	struct qcom_rng_ctx *ctx = crypto_rng_ctx(tfm);
 	struct qcom_rng *rng = ctx->rng;
-	int ret;
+	int ret = -EFAULT;
+	int read_size = 0;
 
 	ret = clk_prepare_enable(rng->clk);
 	if (ret)
@@ -87,11 +94,14 @@ static int qcom_rng_generate(struct crypto_rng *tfm,
 
 	mutex_lock(&rng->lock);
 
-	ret = qcom_rng_read(rng, dstn, dlen);
+	read_size = qcom_rng_read(rng, dstn, dlen);
 
 	mutex_unlock(&rng->lock);
 	clk_disable_unprepare(rng->clk);
 
+	if (read_size == dlen)
+		ret = 0;
+
 	return ret;
 }
 
@@ -101,6 +111,16 @@ 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)
+{
+	int ret;
+	struct qcom_rng *qrng;
+
+	qrng = (struct qcom_rng *)rng->priv;
+	ret = qcom_rng_read(qrng, data, max);
+	return ret;
+}
+
 static int qcom_rng_enable(struct qcom_rng *rng)
 {
 	u32 val;
@@ -136,7 +156,7 @@ 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;
@@ -157,9 +177,16 @@ 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;
+	const struct qcom_rng_of_data *data;
 	int ret;
 
 	rng = devm_kzalloc(&pdev->dev, sizeof(*rng), GFP_KERNEL);
@@ -177,7 +204,8 @@ 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);
+	data = of_device_get_match_data(&pdev->dev);
+	rng->of_data = (struct qcom_rng_of_data *)data;
 
 	qcom_rng_dev = rng;
 	ret = crypto_register_rng(&qcom_rng_alg);
@@ -185,6 +213,14 @@ static int qcom_rng_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "Register crypto rng failed: %d\n", ret);
 		qcom_rng_dev = NULL;
 	}
+	if (rng->of_data->hwrng_support) {
+		qcom_hwrng.priv = (unsigned long)qcom_rng_dev;
+		ret = hwrng_register(&qcom_hwrng);
+		if (ret) {
+			dev_err(&pdev->dev, "Register hwrng failed: %d\n", ret);
+			qcom_rng_dev = NULL;
+		}
+	}
 
 	return ret;
 }
@@ -193,11 +229,29 @@ static int qcom_rng_remove(struct platform_device *pdev)
 {
 	crypto_unregister_rng(&qcom_rng_alg);
 
+	if (qcom_rng_dev->of_data->hwrng_support)
+		hwrng_unregister(&qcom_hwrng);
+
 	qcom_rng_dev = NULL;
 
 	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 +259,9 @@ 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