[PATCH 2/3] mmc: sdhci-xenon: Try to fix 2G address limitation on AC5 SoC

[Vadym Kochan <vadym.kochan@plvision.eu>]

There is a limitation on AC5 SoC that Xenon SDHC can address only
first 2GB of memory. Turning to the SDMA mode to use the bounce_buffer
causes ext_csd recognition to fail on init.

Using of swiotlb=force also does not help as it is allocated at the
end of the memory.

So it was decided to use reserved-memory as a bounce buffer in case
if the board has more than 2G of memory, or turn on the PIO
mode if such memory region does not exist in the device-tree.

It was tested that this approach is 1.5 times faster than PIO.

Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
---
 drivers/mmc/host/sdhci-xenon.c | 36 ++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
index 08e838400b52..fbbd1a045002 100644
--- a/drivers/mmc/host/sdhci-xenon.c
+++ b/drivers/mmc/host/sdhci-xenon.c
@@ -14,8 +14,10 @@
 #include <linux/acpi.h>
 #include <linux/delay.h>
 #include <linux/ktime.h>
+#include <linux/mm.h>
 #include <linux/module.h>
 #include <linux/of.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/pm.h>
 #include <linux/pm_runtime.h>
 
@@ -486,6 +488,31 @@ static void xenon_sdhc_unprepare(struct sdhci_host *host)
 	xenon_disable_sdhc(host, sdhc_id);
 }
 
+static int xenon_ac5_probe(struct sdhci_host *host)
+{
+	struct device *dev = mmc_dev(host->mmc);
+	struct sysinfo si;
+	int err;
+
+	si_meminfo(&si);
+
+	if ((si.totalram * si.mem_unit) > SZ_2G) {
+		struct device_node *dma_bounce_np;
+
+		dma_bounce_np = of_parse_phandle(dev->of_node,
+						 "marvell,ac5-sdhci-dma-bounce-pool", 0);
+		err = of_reserved_mem_device_init_by_idx(dev, dma_bounce_np, 0);
+		of_node_put(dma_bounce_np);
+		if (err) {
+			dev_warn(dev, "Disabling DMA because of 2GB DMA access limit and missing DMA bounce region\n");
+			host->quirks |= SDHCI_QUIRK_BROKEN_ADMA;
+			host->quirks |= SDHCI_QUIRK_BROKEN_DMA;
+		}
+	}
+
+	return 0;
+}
+
 static int xenon_probe(struct platform_device *pdev)
 {
 	struct sdhci_pltfm_host *pltfm_host;
@@ -531,6 +558,12 @@ static int xenon_probe(struct platform_device *pdev)
 			if (err)
 				goto err_clk;
 		}
+
+		if (of_device_is_compatible(dev->of_node, "marvell,ac5-sdhci")) {
+			err = xenon_ac5_probe(host);
+			if (err)
+				goto err_clk_axi;
+		}
 	}
 
 	err = mmc_of_parse(host->mmc);
@@ -570,6 +603,7 @@ static int xenon_probe(struct platform_device *pdev)
 	pm_runtime_put_noidle(&pdev->dev);
 	xenon_sdhc_unprepare(host);
 err_clk_axi:
+	of_reserved_mem_device_release(&pdev->dev);
 	clk_disable_unprepare(priv->axi_clk);
 err_clk:
 	clk_disable_unprepare(pltfm_host->clk);
@@ -591,6 +625,7 @@ static int xenon_remove(struct platform_device *pdev)
 	sdhci_remove_host(host, 0);
 
 	xenon_sdhc_unprepare(host);
+	of_reserved_mem_device_release(&pdev->dev);
 	clk_disable_unprepare(priv->axi_clk);
 	clk_disable_unprepare(pltfm_host->clk);
 
@@ -682,6 +717,7 @@ static const struct of_device_id sdhci_xenon_dt_ids[] = {
 	{ .compatible = "marvell,armada-ap807-sdhci", .data = (void *)XENON_AP807},
 	{ .compatible = "marvell,armada-cp110-sdhci", .data =  (void *)XENON_CP110},
 	{ .compatible = "marvell,armada-3700-sdhci", .data =  (void *)XENON_A3700},
+	{ .compatible = "marvell,ac5-sdhci", .data = (void *)XENON_AP806},
 	{}
 };
 MODULE_DEVICE_TABLE(of, sdhci_xenon_dt_ids);
-- 
2.17.1