mmc: sdhci-esdhc-mcf: Use sg_miter for swapping

Use sg_miter iterator instead of sg_virt() and custom code
to loop over the scatterlist. The memory iterator will do
bounce buffering if the page happens to be located in high memory,
which the driver may or may not be using.
Suggested-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/linux-mmc/20240122073423.GA25859@lst.de/Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240127-mmc-proper-kmap-v2-8-d8e732aa97d1@linaro.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci-esdhc-mcf.c

@@ -299,9 +299,8 @@ static void esdhc_mcf_pltfm_set_bus_width(struct sdhci_host *host, int width)
 static void esdhc_mcf_request_done(struct sdhci_host *host,
 				   struct mmc_request *mrq)
 {
-	struct scatterlist *sg;
+	struct sg_mapping_iter sgm;
 	u32 *buffer;
-	int i;
 
 	if (!mrq->data || !mrq->data->bytes_xfered)
 		goto exit_done;
@@ -313,10 +312,13 @@ static void esdhc_mcf_request_done(struct sdhci_host *host,
 	 * On mcf5441x there is no hw sdma option/flag to select the dma
 	 * transfer endiannes. A swap after the transfer is needed.
 	 */
-	for_each_sg(mrq->data->sg, sg, mrq->data->sg_len, i) {
-		buffer = (u32 *)sg_virt(sg);
-		esdhc_mcf_buffer_swap32(buffer, sg->length);
+	sg_miter_start(&sgm, mrq->data->sg, mrq->data->sg_len,
+		       SG_MITER_TO_SG | SG_MITER_FROM_SG);
+	while (sg_miter_next(&sgm)) {
+		buffer = sgm.addr;
+		esdhc_mcf_buffer_swap32(buffer, sgm.length);
 	}
+	sg_miter_stop(&sgm);
 
 exit_done:
 	mmc_request_done(host->mmc, mrq);