Revert "mmc: moxart-mmc: Use sg_miter for PIO"

This reverts commit 3ee0e7c3.

The patch is not working for unknown reasons and I would
need access to the hardware to fix the bug.

This shouldn't matter anyway: the Moxa Art is not expected
to use highmem, and sg_miter() is only necessary to have
to properly deal with highmem.
Reported-by: Sergei Antonov <saproj@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Fixes: 3ee0e7c3 ("mmc: moxart-mmc: Use sg_miter for PIO")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240606-mmc-moxart-revert-v1-1-a01c2f40de9c@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/moxart-mmc.c

@@ -131,10 +131,12 @@ struct moxart_host {
 	struct dma_async_tx_descriptor	*tx_desc;
 	struct mmc_host			*mmc;
 	struct mmc_request		*mrq;
+	struct scatterlist		*cur_sg;
 	struct completion		dma_complete;
 	struct completion		pio_complete;
 
-	struct sg_mapping_iter		sg_miter;
+	u32				num_sg;
+	u32				data_remain;
 	u32				data_len;
 	u32				fifo_width;
 	u32				timeout;
@@ -146,6 +148,35 @@ struct moxart_host {
 	bool				is_removed;
 };
 
+static inline void moxart_init_sg(struct moxart_host *host,
+				  struct mmc_data *data)
+{
+	host->cur_sg = data->sg;
+	host->num_sg = data->sg_len;
+	host->data_remain = host->cur_sg->length;
+
+	if (host->data_remain > host->data_len)
+		host->data_remain = host->data_len;
+}
+
+static inline int moxart_next_sg(struct moxart_host *host)
+{
+	int remain;
+	struct mmc_data *data = host->mrq->cmd->data;
+
+	host->cur_sg++;
+	host->num_sg--;
+
+	if (host->num_sg > 0) {
+		host->data_remain = host->cur_sg->length;
+		remain = host->data_len - data->bytes_xfered;
+		if (remain > 0 && remain < host->data_remain)
+			host->data_remain = remain;
+	}
+
+	return host->num_sg;
+}
+
 static int moxart_wait_for_status(struct moxart_host *host,
 				  u32 mask, u32 *status)
 {
@@ -278,29 +309,14 @@ static void moxart_transfer_dma(struct mmc_data *data, struct moxart_host *host)
 
 static void moxart_transfer_pio(struct moxart_host *host)
 {
-	struct sg_mapping_iter *sgm = &host->sg_miter;
 	struct mmc_data *data = host->mrq->cmd->data;
 	u32 *sgp, len = 0, remain, status;
 
 	if (host->data_len == data->bytes_xfered)
 		return;
 
-	/*
-	 * By updating sgm->consumes this will get a proper pointer into the
-	 * buffer at any time.
-	 */
-	if (!sg_miter_next(sgm)) {
-		/* This shold not happen */
-		dev_err(mmc_dev(host->mmc), "ran out of scatterlist prematurely\n");
-		data->error = -EINVAL;
-		complete(&host->pio_complete);
-		return;
-	}
-	sgp = sgm->addr;
-	remain = sgm->length;
-	if (remain > host->data_len)
-		remain = host->data_len;
-	sgm->consumed = 0;
+	sgp = sg_virt(host->cur_sg);
+	remain = host->data_remain;
 
 	if (data->flags & MMC_DATA_WRITE) {
 		while (remain > 0) {
@@ -315,7 +331,6 @@ static void moxart_transfer_pio(struct moxart_host *host)
 				sgp++;
 				len += 4;
 			}
-			sgm->consumed += len;
 			remain -= len;
 		}
 
@@ -332,22 +347,22 @@ static void moxart_transfer_pio(struct moxart_host *host)
 				sgp++;
 				len += 4;
 			}
-			sgm->consumed += len;
 			remain -= len;
 		}
 	}
 
-	data->bytes_xfered += sgm->consumed;
-	if (host->data_len == data->bytes_xfered) {
+	data->bytes_xfered += host->data_remain - remain;
+	host->data_remain = remain;
+
+	if (host->data_len != data->bytes_xfered)
+		moxart_next_sg(host);
+	else
 		complete(&host->pio_complete);
-		return;
-	}
 }
 
 static void moxart_prepare_data(struct moxart_host *host)
 {
 	struct mmc_data *data = host->mrq->cmd->data;
-	unsigned int flags = SG_MITER_ATOMIC; /* Used from IRQ */
 	u32 datactrl;
 	int blksz_bits;
 
@@ -358,19 +373,15 @@ static void moxart_prepare_data(struct moxart_host *host)
 	blksz_bits = ffs(data->blksz) - 1;
 	BUG_ON(1 << blksz_bits != data->blksz);
 
+	moxart_init_sg(host, data);
+
 	datactrl = DCR_DATA_EN | (blksz_bits & DCR_BLK_SIZE);
 
-	if (data->flags & MMC_DATA_WRITE) {
-		flags |= SG_MITER_FROM_SG;
+	if (data->flags & MMC_DATA_WRITE)
 		datactrl |= DCR_DATA_WRITE;
-	} else {
-		flags |= SG_MITER_TO_SG;
-	}
 
 	if (moxart_use_dma(host))
 		datactrl |= DCR_DMA_EN;
-	else
-		sg_miter_start(&host->sg_miter, data->sg, data->sg_len, flags);
 
 	writel(DCR_DATA_FIFO_RESET, host->base + REG_DATA_CONTROL);
 	writel(MASK_DATA | FIFO_URUN | FIFO_ORUN, host->base + REG_CLEAR);
@@ -443,9 +454,6 @@ static void moxart_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	}
 
 request_done:
-	if (!moxart_use_dma(host))
-		sg_miter_stop(&host->sg_miter);
-
 	spin_unlock_irqrestore(&host->lock, flags);
 	mmc_request_done(host->mmc, mrq);
 }