[PATCH v6 3/3] mmc: sdhci-of-dwcmshc: solve 128MB DMA boundary limitation

[Jisheng Zhang <Jisheng.Zhang@synaptics.com>]

When using DMA, if the DMA addr spans 128MB boundary, we have to split
the DMA transfer into two so that each one doesn't exceed the boundary.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
---
 drivers/mmc/host/sdhci-of-dwcmshc.c | 39 +++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
index 1b7cd144fb01..a5137845a1c7 100644
--- a/drivers/mmc/host/sdhci-of-dwcmshc.c
+++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
@@ -8,21 +8,51 @@
  */
 
 #include <linux/clk.h>
+#include <linux/dma-mapping.h>
+#include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/sizes.h>
 
 #include "sdhci-pltfm.h"
 
+#define BOUNDARY_OK(addr, len) \
+	((addr | (SZ_128M - 1)) == ((addr + len - 1) | (SZ_128M - 1)))
+
 struct dwcmshc_priv {
 	struct clk	*bus_clk;
 };
 
+/*
+ * If DMA addr spans 128MB boundary, we split the DMA transfer into two
+ * so that each DMA transfer doesn't exceed the boundary.
+ */
+static void dwcmshc_adma_write_desc(struct sdhci_host *host, void **desc,
+				    dma_addr_t addr, int len, unsigned int cmd)
+{
+	int tmplen, offset;
+
+	if (likely(!len || BOUNDARY_OK(addr, len))) {
+		sdhci_adma_write_desc(host, desc, addr, len, cmd);
+		return;
+	}
+
+	offset = addr & (SZ_128M - 1);
+	tmplen = SZ_128M - offset;
+	sdhci_adma_write_desc(host, desc, addr, tmplen, cmd);
+
+	addr += tmplen;
+	len -= tmplen;
+	sdhci_adma_write_desc(host, desc, addr, len, cmd);
+}
+
 static const struct sdhci_ops sdhci_dwcmshc_ops = {
 	.set_clock		= sdhci_set_clock,
 	.set_bus_width		= sdhci_set_bus_width,
 	.set_uhs_signaling	= sdhci_set_uhs_signaling,
 	.get_max_clock		= sdhci_pltfm_clk_get_max_clock,
 	.reset			= sdhci_reset,
+	.adma_write_desc	= dwcmshc_adma_write_desc,
 };
 
 static const struct sdhci_pltfm_data sdhci_dwcmshc_pdata = {
@@ -36,12 +66,21 @@ static int dwcmshc_probe(struct platform_device *pdev)
 	struct sdhci_host *host;
 	struct dwcmshc_priv *priv;
 	int err;
+	u32 extra;
 
 	host = sdhci_pltfm_init(pdev, &sdhci_dwcmshc_pdata,
 				sizeof(struct dwcmshc_priv));
 	if (IS_ERR(host))
 		return PTR_ERR(host);
 
+	/*
+	 * extra adma table cnt for cross 128M boundary handling.
+	 */
+	extra = DIV_ROUND_UP_ULL(dma_get_required_mask(&pdev->dev), SZ_128M);
+	if (extra > SDHCI_MAX_SEGS)
+		extra = SDHCI_MAX_SEGS;
+	host->adma_table_cnt += extra;
+
 	pltfm_host = sdhci_priv(host);
 	priv = sdhci_pltfm_priv(pltfm_host);
 
-- 
2.18.0