[PATCH] mmc: meson-gx: use memcpy_to/fromio for dram-access-quirk

[Neil Armstrong]

It has been reported that usage of memcpy() to/from an iomem mapping is invalid,
and a recent arm64 memcpy update [1] triggers a memory abort when dram-access-quirk
is used on the G12A/G12B platforms.

This adds a local sg_copy_to_buffer which makes usage of io versions of memcpy
when dram-access-quirk is enabled.

Fixes: acdc8e71d9bb ("mmc: meson-gx: add dram-access-quirk")
Reported-by: Marek Szyprowski <m.szyprowski at samsung.com>
Suggested-by: Mark Rutland <mark.rutland at arm.com>
Signed-off-by: Neil Armstrong <narmstrong at baylibre.com>
Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>

[1] 285133040e6c ("arm64: Import latest memcpy()/memmove() implementation")
---
 drivers/mmc/host/meson-gx-mmc.c | 50 +++++++++++++++++++++++++++++----
 1 file changed, 45 insertions(+), 5 deletions(-)


Changes since RFC:
- moved iomem address to bounce_iomem_buf otherwise sparse screamed when feeding memcpy_to/fromio with non iomem pointer

diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
index b8b771b643cc..3e9b28f18c70 100644
--- a/drivers/mmc/host/meson-gx-mmc.c
+++ b/drivers/mmc/host/meson-gx-mmc.c
@@ -165,6 +165,7 @@ struct meson_host {
 
 	unsigned int bounce_buf_size;
 	void *bounce_buf;
+	void __iomem *bounce_iomem_buf;
 	dma_addr_t bounce_dma_addr;
 	struct sd_emmc_desc *descs;
 	dma_addr_t descs_dma_addr;
@@ -742,6 +743,47 @@ static void meson_mmc_desc_chain_transfer(struct mmc_host *mmc, u32 cmd_cfg)
 	writel(start, host->regs + SD_EMMC_START);
 }
 
+/* local sg copy to buffer version with _to/fromio usage for dram_access_quirk */
+static void meson_mmc_copy_buffer(struct meson_host *host, struct mmc_data *data,
+				  size_t buflen, bool to_buffer)
+{
+	unsigned int sg_flags = SG_MITER_ATOMIC;
+	struct scatterlist *sgl = data->sg;
+	unsigned int nents = data->sg_len;
+	struct sg_mapping_iter miter;
+	unsigned int offset = 0;
+
+	if (to_buffer)
+		sg_flags |= SG_MITER_FROM_SG;
+	else
+		sg_flags |= SG_MITER_TO_SG;
+
+	sg_miter_start(&miter, sgl, nents, sg_flags);
+
+	while ((offset < buflen) && sg_miter_next(&miter)) {
+		unsigned int len;
+
+		len = min(miter.length, buflen - offset);
+
+		/* When dram_access_quirk, the bounce buffer is a iomem mapping */
+		if (host->dram_access_quirk) {
+			if (to_buffer)
+				memcpy_toio(host->bounce_iomem_buf + offset, miter.addr, len);
+			else
+				memcpy_fromio(miter.addr, host->bounce_iomem_buf + offset, len);
+		} else {
+			if (to_buffer)
+				memcpy(host->bounce_buf + offset, miter.addr, len);
+			else
+				memcpy(miter.addr, host->bounce_buf + offset, len);
+		}
+
+		offset += len;
+	}
+
+	sg_miter_stop(&miter);
+}
+
 static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
 {
 	struct meson_host *host = mmc_priv(mmc);
@@ -785,8 +827,7 @@ static void meson_mmc_start_cmd(struct mmc_host *mmc, struct mmc_command *cmd)
 		if (data->flags & MMC_DATA_WRITE) {
 			cmd_cfg |= CMD_CFG_DATA_WR;
 			WARN_ON(xfer_bytes > host->bounce_buf_size);
-			sg_copy_to_buffer(data->sg, data->sg_len,
-					  host->bounce_buf, xfer_bytes);
+			meson_mmc_copy_buffer(host, data, xfer_bytes, true);
 			dma_wmb();
 		}
 
@@ -955,8 +996,7 @@ static irqreturn_t meson_mmc_irq_thread(int irq, void *dev_id)
 	if (meson_mmc_bounce_buf_read(data)) {
 		xfer_bytes = data->blksz * data->blocks;
 		WARN_ON(xfer_bytes > host->bounce_buf_size);
-		sg_copy_from_buffer(data->sg, data->sg_len,
-				    host->bounce_buf, xfer_bytes);
+		meson_mmc_copy_buffer(host, data, xfer_bytes, false);
 	}
 
 	next_cmd = meson_mmc_get_next_command(cmd);
@@ -1176,7 +1216,7 @@ static int meson_mmc_probe(struct platform_device *pdev)
 		 * instead of the DDR memory
 		 */
 		host->bounce_buf_size = SD_EMMC_SRAM_DATA_BUF_LEN;
-		host->bounce_buf = host->regs + SD_EMMC_SRAM_DATA_BUF_OFF;
+		host->bounce_iomem_buf = host->regs + SD_EMMC_SRAM_DATA_BUF_OFF;
 		host->bounce_dma_addr = res->start + SD_EMMC_SRAM_DATA_BUF_OFF;
 	} else {
 		/* data bounce buffer */
-- 
2.25.1