crypto: omap-sham - make fallback size configurable

Crypto driver fallback size can now be configured from userspace. This
allows optimizing the DMA usage based on use case. Default fallback
size of 256 is still used.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/omap-sham.c

@@ -229,6 +229,7 @@ struct omap_sham_dev {
 	u8			xmit_buf[BUFLEN] OMAP_ALIGNED;
 
 	unsigned long		flags;
+	int			fallback_sz;
 	struct crypto_queue	queue;
 	struct ahash_request	*req;
 
@@ -1009,7 +1010,7 @@ static int omap_sham_update_req(struct omap_sham_dev *dd)
 		 ctx->total, ctx->digcnt, (ctx->flags & BIT(FLAGS_FINUP)) != 0);
 
 	if (ctx->total < get_block_size(ctx) ||
-	    ctx->total < OMAP_SHA_DMA_THRESHOLD)
+	    ctx->total < dd->fallback_sz)
 		ctx->flags |= BIT(FLAGS_CPU);
 
 	if (ctx->flags & BIT(FLAGS_CPU))
@@ -1265,11 +1266,11 @@ static int omap_sham_final(struct ahash_request *req)
 	/*
 	 * OMAP HW accel works only with buffers >= 9.
 	 * HMAC is always >= 9 because ipad == block size.
-	 * If buffersize is less than DMA_THRESHOLD, we use fallback
+	 * If buffersize is less than fallback_sz, we use fallback
 	 * SW encoding, as using DMA + HW in this case doesn't provide
 	 * any benefit.
 	 */
-	if (!ctx->digcnt && ctx->bufcnt < OMAP_SHA_DMA_THRESHOLD)
+	if (!ctx->digcnt && ctx->bufcnt < ctx->dd->fallback_sz)
 		return omap_sham_final_shash(req);
 	else if (ctx->bufcnt)
 		return omap_sham_enqueue(req, OP_FINAL);
@@ -2020,6 +2021,47 @@ err:
 	return err;
 }
 
+static ssize_t fallback_show(struct device *dev, struct device_attribute *attr,
+			     char *buf)
+{
+	struct omap_sham_dev *dd = dev_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", dd->fallback_sz);
+}
+
+static ssize_t fallback_store(struct device *dev, struct device_attribute *attr,
+			      const char *buf, size_t size)
+{
+	struct omap_sham_dev *dd = dev_get_drvdata(dev);
+	ssize_t status;
+	long value;
+
+	status = kstrtol(buf, 0, &value);
+	if (status)
+		return status;
+
+	/* HW accelerator only works with buffers > 9 */
+	if (value < 9) {
+		dev_err(dev, "minimum fallback size 9\n");
+		return -EINVAL;
+	}
+
+	dd->fallback_sz = value;
+
+	return size;
+}
+
+static DEVICE_ATTR_RW(fallback);
+
+static struct attribute *omap_sham_attrs[] = {
+	&dev_attr_fallback.attr,
+	NULL,
+};
+
+static struct attribute_group omap_sham_attr_group = {
+	.attrs = omap_sham_attrs,
+};
+
 static int omap_sham_probe(struct platform_device *pdev)
 {
 	struct omap_sham_dev *dd;
@@ -2081,6 +2123,8 @@ static int omap_sham_probe(struct platform_device *pdev)
 	pm_runtime_use_autosuspend(dev);
 	pm_runtime_set_autosuspend_delay(dev, DEFAULT_AUTOSUSPEND_DELAY);
 
+	dd->fallback_sz = OMAP_SHA_DMA_THRESHOLD;
+
 	pm_runtime_enable(dev);
 	pm_runtime_irq_safe(dev);
 
@@ -2118,6 +2162,12 @@ static int omap_sham_probe(struct platform_device *pdev)
 		}
 	}
 
+	err = sysfs_create_group(&dev->kobj, &omap_sham_attr_group);
+	if (err) {
+		dev_err(dev, "could not create sysfs device attrs\n");
+		goto err_algs;
+	}
+
 	return 0;
 
 err_algs: