[PATCH] mmc: sdhci-sirf: enable dmabounce since SiRFprimaII MMC DMA only access up to 256MB

[Barry Song]

From: Bin Shi <Bin.Shi at csr.com>

on SiRFprimaII, sdhci is after pci-iobg bus, the bus bridge has a hardware
limitation. DMA operations after this bridge can not access memory address
higher than 256MB.

this patch enables dmabounce for SiRFprimaII to fix DMA of primaII. for other
SiRF SoCs, there is no this problem.

Signed-off-by: Bin Shi <Bin.Shi at csr.com>
Signed-off-by: Binghua Duan <Binghua.Duan at csr.com>
Signed-off-by: Barry Song <Baohua.Song at csr.com>
---
 arch/arm/mach-prima2/Kconfig  |  1 +
 drivers/mmc/host/sdhci-sirf.c | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/arch/arm/mach-prima2/Kconfig b/arch/arm/mach-prima2/Kconfig
index 6988b11..8ecb071 100644
--- a/arch/arm/mach-prima2/Kconfig
+++ b/arch/arm/mach-prima2/Kconfig
@@ -26,6 +26,7 @@ config ARCH_PRIMA2
 	bool "CSR SiRFSoC PRIMA2 ARM Cortex A9 Platform"
 	default y
 	select CPU_V7
+	select DMABOUNCE
 	select SIRF_IRQ
 	select ZONE_DMA
 	help
diff --git a/drivers/mmc/host/sdhci-sirf.c b/drivers/mmc/host/sdhci-sirf.c
index 696122c..11e270f 100644
--- a/drivers/mmc/host/sdhci-sirf.c
+++ b/drivers/mmc/host/sdhci-sirf.c
@@ -13,6 +13,7 @@
 #include <linux/of.h>
 #include <linux/of_gpio.h>
 #include <linux/mmc/slot-gpio.h>
+#include <linux/dma-mapping.h>
 #include "sdhci-pltfm.h"
 
 struct sdhci_sirf_priv {
@@ -40,6 +41,16 @@ static struct sdhci_pltfm_data sdhci_sirf_pdata = {
 		SDHCI_QUIRK_DELAY_AFTER_POWER,
 };
 
+/*
+ * The following functions are needed for DMA bouncing because SiRFprimaII SD
+ * controller can address up to 256MByte
+ */
+static int sdhci_sirf_needs_bounce(struct device *dev, dma_addr_t dma_addr,
+	size_t size)
+{
+	return (dma_addr + size) >= SZ_256M;
+}
+
 static int sdhci_sirf_probe(struct platform_device *pdev)
 {
 	struct sdhci_host *host;
@@ -92,6 +103,13 @@ static int sdhci_sirf_probe(struct platform_device *pdev)
 		}
 	}
 
+	if (of_machine_is_compatible("sirf,prima2")) {
+		if (pdev->dev.dma_mask)
+			*(pdev->dev.dma_mask) = SZ_256M - 1;
+		pdev->dev.coherent_dma_mask = SZ_256M - 1;
+		dmabounce_register_dev(&pdev->dev, 1024, 2048, sdhci_sirf_needs_bounce);
+	}
+
 	return 0;
 
 err_request_cd:
-- 
1.8.2.3