crypto: omap-sham - Enable Polling mode if DMA fails

For writing input buffer into DATA_IN register current driver
has the following state machine:
-> if input buffer < 9 : use fallback driver
-> else if input buffer < block size : Copy input buffer into data_in regs
-> else use dma transfer.

In cases where requesting for DMA channels fails for some reason,
or channel numbers are not provided in DT or platform data, probe
also fails. Instead of returning from driver use cpu polling mode.
In this mode processor polls on INPUT_READY bit and writes data into
data_in regs when it equals 1. This operation is repeated until the
length of message.

Now the state machine looks like:
-> if input buffer < 9 : use fallback driver
-> else if input buffer < block size : Copy input buffer into data_in regs
-> else if dma enabled: use dma transfer
else use cpu polling mode.

Signed-off-by: Lokesh Vutla <[e-mail]>
Signed-off-by: Herbert Xu <[e-mail]>

drivers/crypto/omap-sham.c

···
 	unsigned int		dma;
 	struct dma_chan		*dma_lch;
 	struct tasklet_struct	done_task;
+	u8			polling_mode;
 
 	unsigned long		flags;
 	struct crypto_queue	queue;
···
 			      size_t length, int final)
 {
 	struct omap_sham_reqctx *ctx = ahash_request_ctx(dd->req);
-	int count, len32;
+	int count, len32, bs32, offset = 0;
 	const u32 *buffer = (const u32 *)buf;
 
 	dev_dbg(dd->dev, "xmit_cpu: digcnt: %d, length: %d, final: %d\n",
···
 	/* should be non-zero before next lines to disable clocks later */
 	ctx->digcnt += length;
 
-	if (dd->pdata->poll_irq(dd))
-		return -ETIMEDOUT;
-
 	if (final)
 		set_bit(FLAGS_FINAL, &dd->flags); /* catch last interrupt */
 
 	set_bit(FLAGS_CPU, &dd->flags);
 
 	len32 = DIV_ROUND_UP(length, sizeof(u32));
+	bs32 = get_block_size(ctx) / sizeof(u32);
 
-	for (count = 0; count < len32; count++)
-		omap_sham_write(dd, SHA_REG_DIN(dd, count), buffer[count]);
+	while (len32) {
+		if (dd->pdata->poll_irq(dd))
+			return -ETIMEDOUT;
+
+		for (count = 0; count < min(len32, bs32); count++, offset++)
+			omap_sham_write(dd, SHA_REG_DIN(dd, count),
+					buffer[offset]);
+		len32 -= min(len32, bs32);
+	}
 
 	return -EINPROGRESS;
 }
···
 static int omap_sham_update_cpu(struct omap_sham_dev *dd)
 {
 	struct omap_sham_reqctx *ctx = ahash_request_ctx(dd->req);
-	int bufcnt;
+	int bufcnt, final;
+
+	if (!ctx->total)
+		return 0;
 
 	omap_sham_append_sg(ctx);
+
+	final = (ctx->flags & BIT(FLAGS_FINUP)) && !ctx->total;
+
+	dev_dbg(dd->dev, "cpu: bufcnt: %u, digcnt: %d, final: %d\n",
+		ctx->bufcnt, ctx->digcnt, final);
+
 	bufcnt = ctx->bufcnt;
 	ctx->bufcnt = 0;
 
-	return omap_sham_xmit_cpu(dd, ctx->buffer, bufcnt, 1);
+	return omap_sham_xmit_cpu(dd, ctx->buffer, bufcnt, final);
 }
 
 static int omap_sham_update_dma_stop(struct omap_sham_dev *dd)
···
 	struct omap_sham_reqctx *ctx = ahash_request_ctx(req);
 	int err = 0, use_dma = 1;
 
-	if (ctx->bufcnt <= DMA_MIN)
-		/* faster to handle last block with cpu */
+	if ((ctx->bufcnt <= get_block_size(ctx)) || dd->polling_mode)
+		/*
+		 * faster to handle last block with cpu or
+		 * use cpu when dma is not present.
+		 */
 		use_dma = 0;
 
 	if (use_dma)
···
 static int omap_sham_update(struct ahash_request *req)
 {
 	struct omap_sham_reqctx *ctx = ahash_request_ctx(req);
+	struct omap_sham_dev *dd = ctx->dd;
 	int bs = get_block_size(ctx);
 
 	if (!req->nbytes)
···
 			*/
 			omap_sham_append_sg(ctx);
 			return 0;
-		} else if (ctx->bufcnt + ctx->total <= bs) {
+		} else if ((ctx->bufcnt + ctx->total <= bs) ||
+			   dd->polling_mode) {
 			/*
-			* faster to use CPU for short transfers
-			*/
+			 * faster to use CPU for short transfers or
+			 * use cpu when dma is not present.
+			 */
 			ctx->flags |= BIT(FLAGS_CPU);
 		}
 	} else if (ctx->bufcnt + ctx->total < ctx->buflen) {
···
 	}
 
 	if (test_bit(FLAGS_CPU, &dd->flags)) {
-		if (test_and_clear_bit(FLAGS_OUTPUT_READY, &dd->flags))
-			goto finish;
+		if (test_and_clear_bit(FLAGS_OUTPUT_READY, &dd->flags)) {
+			/* hash or semi-hash ready */
+			err = omap_sham_update_cpu(dd);
+			if (err != -EINPROGRESS)
+				goto finish;
+		}
 	} else if (test_bit(FLAGS_DMA_READY, &dd->flags)) {
 		if (test_and_clear_bit(FLAGS_DMA_ACTIVE, &dd->flags)) {
 			omap_sham_update_dma_stop(dd);
···
 	dd->dma_lch = dma_request_slave_channel_compat(mask, omap_dma_filter_fn,
 						       &dd->dma, dev, "rx");
 	if (!dd->dma_lch) {
-		dev_err(dev, "unable to obtain RX DMA engine channel %u\n",
-			dd->dma);
-		err = -ENXIO;
-		goto data_err;
+		dd->polling_mode = 1;
+		dev_dbg(dev, "using polling mode instead of dma\n");
 	}
 
 	dd->flags |= dd->pdata->flags;