crypto: qcom-rng - Add hw_random interface support

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@quicinc.com>
Reviewed-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Om Prakash Singh <quic_omprsing@quicinc.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

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>
@@ -28,17 +29,25 @@
 
 #define WORD_SZ			4
 
+#define QCOM_TRNG_QUALITY	1024
+
 struct qcom_rng {
 	struct mutex lock;
 	void __iomem *base;
 	struct clk *clk;
-	unsigned int skip_init;
+	struct hwrng hwrng;
+	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)
@@ -66,11 +75,11 @@ static int qcom_rng_read(struct qcom_rng *rng, u8 *data, unsigned int max)
 		} else {
 			/* copy only remaining bytes */
 			memcpy(data, &val, max - currsize);
-			break;
+			currsize = max;
 		}
 	} while (currsize < max);
 
-	return 0;
+	return currsize;
 }
 
 static int qcom_rng_generate(struct crypto_rng *tfm,
@@ -92,6 +101,9 @@ static int qcom_rng_generate(struct crypto_rng *tfm,
 	mutex_unlock(&rng->lock);
 	clk_disable_unprepare(rng->clk);
 
+	if (ret >= 0)
+		ret = 0;
+
 	return ret;
 }
 
@@ -101,6 +113,13 @@ static int qcom_rng_seed(struct crypto_rng *tfm, const u8 *seed,
 	return 0;
 }
 
+static int qcom_hwrng_read(struct hwrng *hwrng, void *data, size_t max, bool wait)
+{
+	struct qcom_rng *qrng = container_of(hwrng, struct qcom_rng, hwrng);
+
+	return qcom_rng_read(qrng, data, max);
+}
+
 static int qcom_rng_enable(struct qcom_rng *rng)
 {
 	u32 val;
@@ -136,7 +155,7 @@ 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;
@@ -177,15 +196,31 @@ 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) {
+		rng->hwrng.name = "qcom_hwrng";
+		rng->hwrng.read = qcom_hwrng_read;
+		rng->hwrng.quality = QCOM_TRNG_QUALITY;
+		ret = devm_hwrng_register(&pdev->dev, &rng->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 +233,21 @@ static int qcom_rng_remove(struct platform_device *pdev)
 	return 0;
 }
 
+static struct qcom_rng_of_data qcom_prng_of_data = {
+	.skip_init = false,
+	.hwrng_support = false,
+};
+
+static struct qcom_rng_of_data qcom_prng_ee_of_data = {
+	.skip_init = true,
+	.hwrng_support = false,
+};
+
+static 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 },
 	{}
@@ -205,8 +255,9 @@ 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,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);