[PATCH 3/5] mmc: tmio: sdhi: Use bounce buffer to avoid DMA limitations

[Marek Vasut]

The R-Car SDHI DMA controller has various restrictions. To work around
those restrictions without falling back to PIO, implement bounce buffer
with custom alignment check function which tests for those limitations.

Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck at gmail.com>
Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
Cc: Peng Fan <peng.fan at nxp.com>
Cc: Simon Glass <sjg at chromium.org>
Cc: Tom Rini <trini at konsulko.com>
---
 drivers/mmc/Kconfig        |  1 +
 drivers/mmc/renesas-sdhi.c | 75 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 76 insertions(+)

diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig
index 2f0eedc22f..c69a18007d 100644
--- a/drivers/mmc/Kconfig
+++ b/drivers/mmc/Kconfig
@@ -347,6 +347,7 @@ config RENESAS_SDHI
 	depends on ARCH_RMOBILE
 	depends on BLK && DM_MMC
 	depends on OF_CONTROL
+	select BOUNCE_BUFFER
 	help
 	  This selects support for the Matsushita SD/MMC Host Controller on
 	  Renesas R-Car SoCs.
diff --git a/drivers/mmc/renesas-sdhi.c b/drivers/mmc/renesas-sdhi.c
index c3b13136f8..20c632c4af 100644
--- a/drivers/mmc/renesas-sdhi.c
+++ b/drivers/mmc/renesas-sdhi.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <bouncebuf.h>
 #include <clk.h>
 #include <fdtdec.h>
 #include <malloc.h>
@@ -689,12 +690,86 @@ static int renesas_sdhi_wait_dat0(struct udevice *dev, int state,
 }
 #endif
 
+#define RENESAS_SDHI_DMA_ALIGNMENT	128
+
+static int renesas_sdhi_addr_aligned(struct bounce_buffer *state)
+{
+	uintptr_t ubuf = (uintptr_t)state->user_buffer;
+
+	/* Check if start is aligned */
+	if (!IS_ALIGNED(ubuf, RENESAS_SDHI_DMA_ALIGNMENT)) {
+		debug("Unaligned buffer address %p\n", state->user_buffer);
+		return 0;
+	}
+
+	/* Check if length is aligned */
+	if (state->len != state->len_aligned) {
+		debug("Unaligned buffer length %zu\n", state->len);
+		return 0;
+	}
+
+	/* Check if below 32bit boundary */
+	if ((ubuf >> 32) || (ubuf + state->len_aligned) >> 32) {
+		debug("Buffer above 32bit boundary %p-%p\n",
+			state->user_buffer,
+			state->user_buffer + state->len_aligned);
+		return 0;
+	}
+
+	/* Aligned */
+	return 1;
+}
+
 static int renesas_sdhi_send_cmd(struct udevice *dev, struct mmc_cmd *cmd,
 				 struct mmc_data *data)
 {
+	struct bounce_buffer bbstate;
+	unsigned int bbflags;
+	bool bbok = false;
+	size_t len;
+	void *buf;
 	int ret;
 
+	if (data) {
+		if (data->flags & MMC_DATA_READ) {
+			buf = data->dest;
+			bbflags = GEN_BB_WRITE;
+		} else {
+			buf = (void *)data->src;
+			bbflags = GEN_BB_READ;
+		}
+		len = data->blocks * data->blocksize;
+
+		ret = bounce_buffer_start_extalign(&bbstate, buf, len, bbflags,
+						   RENESAS_SDHI_DMA_ALIGNMENT,
+						   renesas_sdhi_addr_aligned);
+		/*
+		 * If the amount of data to transfer is too large, we can get
+		 * -ENOMEM when starting the bounce buffer. If that happens,
+		 *  fall back to PIO as it was before, otherwise use the BB.
+		 */
+		if (!ret) {
+			bbok = true;
+			if (data->flags & MMC_DATA_READ)
+				data->dest = bbstate.bounce_buffer;
+			else
+				data->src = bbstate.bounce_buffer;
+		}
+	}
+
 	ret = tmio_sd_send_cmd(dev, cmd, data);
+
+	if (data && bbok) {
+		buf = bbstate.user_buffer;
+
+		bounce_buffer_stop(&bbstate);
+
+		if (data->flags & MMC_DATA_READ)
+			data->dest = buf;
+		else
+			data->src = buf;
+	}
+
 	if (ret)
 		return ret;
 
-- 
2.25.0