Sets the EMC clock rate based on the bandwidth requirements registered by
memory clients through the PM_QOS_MEMORY_BANDWIDTH class.
Note: this is just an example and not a proper driver for a external memory
controller. Its only purpose is to illustrate how such a driver would set the
frequency of the external memory clock based on the bandwidth requirements of
memory clients.
---
v4: * Add hack so the driver gets actually registered.
* Use the tegra-clk-debug dev_id to query the EMC clock
* Get units right and use types consistently
---
arch/arm/mach-tegra/tegra.c | 10 ++++
drivers/memory/Kconfig | 9 ++++
drivers/memory/Makefile | 1 +
drivers/memory/tegra124-emc.c | 117 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 137 insertions(+)
create mode 100644 drivers/memory/tegra124-emc.c
diff --git a/arch/arm/mach-tegra/tegra.c b/arch/arm/mach-tegra/tegra.c
index 5ef5173..099d8e7f 100644
--- a/arch/arm/mach-tegra/tegra.c
+++ b/arch/arm/mach-tegra/tegra.c
@@ -70,6 +70,11 @@ u32 tegra_uart_config[3] = {
0,
};
+static struct platform_device tegra_emc = {
+ .name = "tegra124-emc",
+ .id = -1,
+};
+
static void __init tegra_init_early(void)
{
of_register_trusted_foundations();
@@ -112,6 +117,11 @@ static void __init tegra_dt_init(void)
parent = soc_device_to_device(soc_dev);
/*
+ * HACK: register a platform device to probe the driver
+ */
+ platform_device_register(&tegra_emc);
+
+ /*
* Finished with the static registrations now; fill in the missing
* devices
*/
diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
index fab81a1..2088b2b 100644
--- a/drivers/memory/Kconfig
+++ b/drivers/memory/Kconfig
@@ -61,6 +61,15 @@ config TEGRA30_MC
analysis, especially for IOMMU/SMMU(System Memory Management
Unit) module.
+config TEGRA124_EMC
+ tristate "Tegra124 External Memory Controller (EMC) driver"
+ default y
+ depends on ARCH_TEGRA_124_SOC
+ help
+ This driver is for the External Memory Controller (EMC) module
+ available in Tegra124 SoCs.
+
+
config FSL_CORENET_CF
tristate "Freescale CoreNet Error Reporting"
depends on FSL_SOC_BOOKE
diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
index 4055c47..0a6d117 100644
--- a/drivers/memory/Makefile
+++ b/drivers/memory/Makefile
@@ -12,3 +12,4 @@ obj-$(CONFIG_FSL_IFC) += fsl_ifc.o
obj-$(CONFIG_MVEBU_DEVBUS) += mvebu-devbus.o
obj-$(CONFIG_TEGRA20_MC) += tegra20-mc.o
obj-$(CONFIG_TEGRA30_MC) += tegra30-mc.o
+obj-$(CONFIG_TEGRA124_EMC) += tegra124-emc.o
diff --git a/drivers/memory/tegra124-emc.c b/drivers/memory/tegra124-emc.c
new file mode 100644
index 0000000..a290ad5
--- /dev/null
+++ b/drivers/memory/tegra124-emc.c
@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2013, NVIDIA CORPORATION. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/clk.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pm_qos.h>
+
+#define DRV_NAME "tegra124-emc"
+#define EMC_FREQ_CUTOFF_USE_130_PERCENT 100000000
+#define EMC_FREQ_CUTOFF_USE_140_PERCENT 50000000
+#define BYTES_PER_EMC_CLOCK 16
+
+struct tegra124_emc {
+ struct clk *clk;
+ struct notifier_block memory_bw_notifier;
+};
+
+static struct platform_device *emc_pdev;
+
+static unsigned long tegra124_emc_bw_to_freq_req(s32 bw)
+{
+ return (bw * 8 + BYTES_PER_EMC_CLOCK - 1) / BYTES_PER_EMC_CLOCK;
+}
+
+static void tegra124_emc_update_rate(struct tegra124_emc *emc, s32 total_bandwidth)
+{
+ struct clk *emc_master;
+ unsigned long freq;
+
+ emc_master = clk_get_parent(emc->clk);
+ freq = tegra124_emc_bw_to_freq_req(total_bandwidth * 1024);
+ freq = clk_round_rate(emc_master, freq);
+
+ /* Depending on frequency value, the amount of bandwidth usage % of
+ * total we should use is different. Thus we should request a multiple of
+ * original bandwidth on this. Use 1.4 for < 50MHz, 1.3 for < 100MHz,
+ * else 1.1 */
+ if (freq < EMC_FREQ_CUTOFF_USE_140_PERCENT)
+ total_bandwidth += 4 * total_bandwidth / 10; /* 1.4 */
+ else if (freq < EMC_FREQ_CUTOFF_USE_130_PERCENT)
+ total_bandwidth += 3 * total_bandwidth / 10; /* 1.3 */
+ else
+ total_bandwidth += total_bandwidth / 10; /* 1.1 */
+
+ freq = tegra124_emc_bw_to_freq_req(total_bandwidth * 1024);
+
+ clk_set_floor_rate(emc->clk, freq);
+}
+
+int memory_bw_notify(struct notifier_block *nb, unsigned long data, void *dummy)
+{
+ s32 total_bw = (s32) data;
+ struct tegra124_emc *emc =
+ container_of(nb, struct tegra124_emc,
+ memory_bw_notifier);
+
+ tegra124_emc_update_rate(emc, total_bw);
+
+ return NOTIFY_OK;
+}
+
+static int tegra124_emc_probe(struct platform_device *pdev)
+{
+ struct tegra124_emc *emc;
+
+ emc_pdev = pdev;
+
+ emc = devm_kzalloc(&pdev->dev, sizeof(*emc), GFP_KERNEL);
+ if (emc == NULL) {
+ dev_err(&pdev->dev, "Failed to allocate private memory\n");
+ return -ENOMEM;
+ }
+
+ emc->clk = clk_get_sys("tegra-clk-debug", "emc");
+ if (IS_ERR(emc->clk)) {
+ devm_kfree(&pdev->dev, emc);
+ dev_err(&pdev->dev, "Can not find EMC clock\n");
+ return -EPROBE_DEFER;
+ }
+
+ platform_set_drvdata(emc_pdev, emc);
+
+ emc->memory_bw_notifier.notifier_call = memory_bw_notify;
+ pm_qos_add_notifier(PM_QOS_MEMORY_BANDWIDTH, &emc->memory_bw_notifier);
+
+ return 0;
+}
+
+static struct platform_driver tegra124_emc_driver = {
+ .driver = {
+ .name = DRV_NAME,
+ .owner = THIS_MODULE,
+ },
+ .probe = tegra124_emc_probe,
+};
+
+module_platform_driver(tegra124_emc_driver);
+
+MODULE_AUTHOR("Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("Tegra124 EMC driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:" DRV_NAME);
--
1.9.3
--
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