Sets the EMC clock rate based on the bandwidth requirements registered by memory clients through the PM_QOS_MEMORY_BANDWIDTH class. Note: this is 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. Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> --- drivers/memory/Kconfig | 8 +++ drivers/memory/Makefile | 1 + drivers/memory/tegra124-emc.c | 115 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 124 insertions(+) create mode 100644 drivers/memory/tegra124-emc.c diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig index c59e9c9..48fa0dd 100644 --- a/drivers/memory/Kconfig +++ b/drivers/memory/Kconfig @@ -61,6 +61,14 @@ 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_IFC bool depends on FSL_SOC diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile index 71160a2..0b7290b 100644 --- a/drivers/memory/Makefile +++ b/drivers/memory/Makefile @@ -11,3 +11,4 @@ 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..53a34bd --- /dev/null +++ b/drivers/memory/tegra124-emc.c @@ -0,0 +1,115 @@ +/* + * 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/kernel.h> +#include <linux/module.h> +#include <linux/clk.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(unsigned long bw) +{ + return (bw + BYTES_PER_EMC_CLOCK - 1) / BYTES_PER_EMC_CLOCK; +} + +static void tegra124_emc_update_rate(struct tegra124_emc *emc, unsigned long 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) * 1000; + 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) * 1000; + + clk_set_floor_rate(emc->clk, freq); +} + +int memory_bw_notify(struct notifier_block *nb, unsigned long total_bw, void *dummy) +{ + 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(&pdev->dev, "emc"); + if (IS_ERR(emc->clk)) { + devm_kfree(&pdev->dev, emc); + dev_err(&pdev->dev, "Can not find EMC clock\n"); + return -EINVAL; + } + + 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 -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
