Re: [PATCH v4 2/2] memory/mediatek: Add an interface to get current DDR data rate

Krzysztof Kozlowski
2025-04-04T11:11:06Z

Please use subject prefixes matching the subsystem. You can get them for
example with 'git log --oneline -- DIRECTORY_OR_FILE' on the directory
your patch is touching. For bindings, the preferred subjects are
explained here:
https://www.kernel.org/doc/html/latest/devicetree/bindings/submitting-patches.html#i-for-patch-submitters

memory: mediatek:

On Thu, Apr 03, 2025 at 02:48:48PM GMT, Crystal Guo wrote:
> Add MediaTek DRAMC driver to provide an interface that can
> obtain current DDR data rate.
>
> Signed-off-by: Crystal Guo <crystal.guo@mediatek.com>
> ---
> drivers/memory/Kconfig | 1 +
> drivers/memory/Makefile | 1 +
> drivers/memory/mediatek/Kconfig | 20 +++
> drivers/memory/mediatek/Makefile | 2 +
> drivers/memory/mediatek/mtk-dramc.c | 223 ++++++++++++++++++++++++++++
> 5 files changed, 247 insertions(+)
> create mode 100644 drivers/memory/mediatek/Kconfig
> create mode 100644 drivers/memory/mediatek/Makefile
> create mode 100644 drivers/memory/mediatek/mtk-dramc.c
>
> diff --git a/drivers/memory/Kconfig b/drivers/memory/Kconfig
> index c82d8d8a16ea..b1698549ff81 100644
> --- a/drivers/memory/Kconfig
> +++ b/drivers/memory/Kconfig
> @@ -227,5 +227,6 @@ config STM32_FMC2_EBI
>
> source "drivers/memory/samsung/Kconfig"
> source "drivers/memory/tegra/Kconfig"
> +source "drivers/memory/mediatek/Kconfig"

m goes before s, so this goes before samsung source.

>
> endif
> diff --git a/drivers/memory/Makefile b/drivers/memory/Makefile
> index d2e6ca9abbe0..c0facf529803 100644
> --- a/drivers/memory/Makefile
> +++ b/drivers/memory/Makefile
> @@ -27,6 +27,7 @@ obj-$(CONFIG_STM32_FMC2_EBI) += stm32-fmc2-ebi.o
>
> obj-$(CONFIG_SAMSUNG_MC) += samsung/
> obj-$(CONFIG_TEGRA_MC) += tegra/
> +obj-$(CONFIG_MEDIATEK_MC) += mediatek/
> obj-$(CONFIG_TI_EMIF_SRAM) += ti-emif-sram.o
> obj-$(CONFIG_FPGA_DFL_EMIF) += dfl-emif.o
>
> diff --git a/drivers/memory/mediatek/Kconfig b/drivers/memory/mediatek/Kconfig
> new file mode 100644
> index 000000000000..eadc11ec0f1c
> --- /dev/null
> +++ b/drivers/memory/mediatek/Kconfig
> @@ -0,0 +1,20 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config MEDIATEK_MC
> + bool "MediaTek Memory Controller support"
> + default y

Why this has to be enabled for every compile test build? Look how other
platforms do it.

I'll fix the tegra.

> + depends on ARCH_MEDIATEK || COMPILE_TEST
> + help
> + This option allows to enable MediaTek memory controller drivers,
> + which may include controllers for DRAM or others.
> +
> +if MEDIATEK_MC
> +
> +config MTK_DRAMC
> + tristate "MediaTek DRAMC driver"
> + default y

This matters less, could stay or could be also ARCH_MDIATEK.

> + help
> + This driver is for the DRAM Controller found in MediaTek SoCs
> + and provides a sysfs interface for reporting the current DRAM
> + data rate.
> +
> +endif

...

> +
> +static unsigned int read_reg_field(void __iomem *base, unsigned int offset, unsigned int mask)
> +{
> + unsigned int val = readl(base + offset);
> + unsigned int shift = __ffs(mask);
> +
> + return (val & mask) >> shift;
> +}
> +
> +static int mtk_dramc_probe(struct platform_device *pdev)

Weird ordering. probe() is one of the last functions. Only other driver
struct functions (like remove, suspend/resume) go after, not some
regular code.

> +{
> + struct mtk_dramc *dramc;
> + const struct mtk_dramc_pdata *pdata;
> +
> + dramc = devm_kzalloc(&pdev->dev, sizeof(struct mtk_dramc), GFP_KERNEL);
> + if (!dramc)
> + return dev_err_probe(&pdev->dev, -ENOMEM, "Failed to allocate memory\n");
> +
> + pdata = of_device_get_match_data(&pdev->dev);
> + if (!pdata)
> + return dev_err_probe(&pdev->dev, -EINVAL, "No platform data available\n");

Just return. That's impossible condition, so no need for printing errors.

> +
> + dramc->pdata = pdata;

Why do you need pdata variable in the first place? Make this code
simple, not complicated.

> +
> + dramc->anaphy_base = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(dramc->anaphy_base))
> + return dev_err_probe(&pdev->dev, PTR_ERR(dramc->anaphy_base),
> + "Unable to map ANAPHY base\n");
> +
> + dramc->ddrphy_base = devm_platform_ioremap_resource(pdev, 1);
> + if (IS_ERR(dramc->ddrphy_base))
> + return dev_err_probe(&pdev->dev, PTR_ERR(dramc->ddrphy_base),
> + "Unable to map DDRPHY base\n");
> +
> + platform_set_drvdata(pdev, dramc);
> + return 0;
> +}
> +
> +static unsigned int mtk_fmeter_v1(struct mtk_dramc *dramc)
> +{
> + const struct mtk_dramc_pdata *pdata = dramc->pdata;
> + unsigned int shu_level, pll_sel, offset;
> + unsigned int sdmpcw, posdiv, clkdiv, fbksel, sopen, async_ca, ser_mode;
> + unsigned int prediv_freq, posdiv_freq, vco_freq;
> + unsigned int final_rate;
> +
> + shu_level = read_reg_field(dramc->ddrphy_base, pdata->regs[DRAMC_DPHY_DVFS_STA],
> + pdata->masks[DRAMC_DPHY_DVFS_SHU_LV]);

Don't creat your own wrappers. Use existing FIELD_PREP stuff.

> + pll_sel = read_reg_field(dramc->ddrphy_base, pdata->regs[DRAMC_DPHY_DVFS_STA],
> + pdata->masks[DRAMC_DPHY_DVFS_PLL_SEL]);
> + offset = pdata->shuffle_offset * shu_level;
> +
> + sdmpcw = read_reg_field(dramc->anaphy_base,
> + ((pll_sel == 0) ?
> + pdata->regs[DRAMC_APHY_SHU_PHYPLL2] :
> + pdata->regs[DRAMC_APHY_SHU_CLRPLL2]) + offset,
> + pdata->masks[DRAMC_APHY_PLL2_SDMPCW]);
> + posdiv = read_reg_field(dramc->anaphy_base,
> + ((pll_sel == 0) ?
> + pdata->regs[DRAMC_APHY_SHU_PHYPLL3] :
> + pdata->regs[DRAMC_APHY_SHU_CLRPLL3]) + offset,
> + pdata->masks[DRAMC_APHY_PLL3_POSDIV]);
> + fbksel = read_reg_field(dramc->anaphy_base, pdata->regs[DRAMC_APHY_SHU_PHYPLL4] + offset,
> + pdata->masks[DRAMC_APHY_PLL4_FBKSEL]);
> + sopen = read_reg_field(dramc->anaphy_base, pdata->regs[DRAMC_APHY_ARPI0] + offset,
> + pdata->masks[DRAMC_APHY_ARPI0_SOPEN]);
> + async_ca = read_reg_field(dramc->anaphy_base, pdata->regs[DRAMC_APHY_CA_ARDLL1] + offset,
> + pdata->masks[DRAMC_APHY_ARDLL1_CK_EN]);
> + ser_mode = read_reg_field(dramc->anaphy_base, pdata->regs[DRAMC_APHY_B0_TX0] + offset,
> + pdata->masks[DRAMC_APHY_B0_TX0_SER_MODE]);
> +
> + clkdiv = (ser_mode == 1) ? 1 : 0;
> + posdiv &= ~(pdata->posdiv_purify);
> +
> + prediv_freq = pdata->ref_freq_mhz * (sdmpcw >> pdata->prediv);
> + posdiv_freq = (prediv_freq >> posdiv) >> 1;
> + vco_freq = posdiv_freq << fbksel;
> + final_rate = vco_freq >> clkdiv;
> +
> + if (sopen == 1 && async_ca == 1)
> + final_rate >>= 1;
> +
> + return final_rate;
> +}
> +
> +/**
> + * mtk_dramc_get_data_rate - Calculate the current DRAM data rate
> + * @dev: Device pointer
> + *
> + * Return: DRAM Data Rate in Mbps or negative number for error
> + */
> +static unsigned int mtk_dramc_get_data_rate(struct device *dev)
> +{
> + struct mtk_dramc *dramc = dev_get_drvdata(dev);
> +
> + if (dramc->pdata->fmeter_version == 1)

Drop, it's not possible to have other case.

> + return mtk_fmeter_v1(dramc);
> +
> + dev_err(dev, "Frequency meter version %u not supported\n", dramc->pdata->fmeter_version);
> + return -EINVAL;
> +}
> +
> +static ssize_t dram_data_rate_show(struct device *dev,
> + struct device_attribute *attr, char *buf)

No ABI doc.

Why existing interconnect interface is not suitable here? This should
be an interconnect, otherwise what is the point of this driver? What do
you exactly configure here?

> +{
> + return snprintf(buf, PAGE_SIZE, "DRAM data rate = %u\n",
> + mtk_dramc_get_data_rate(dev));
> +}
> +
> +static DEVICE_ATTR_RO(dram_data_rate);
> +
> +static struct attribute *mtk_dramc_attrs[] = {
> + &dev_attr_dram_data_rate.attr,
> + NULL
> +};
> +ATTRIBUTE_GROUPS(mtk_dramc);
> +
> +static const struct mtk_dramc_pdata dramc_pdata_mt8196 = {
> + .fmeter_version = 1,
> + .ref_freq_mhz = 26,
> + .regs = mtk_dramc_regs_mt8196,
> + .masks = mtk_dramc_masks_mt8196,
> + .posdiv_purify = BIT(2),
> + .prediv = 7,
> + .shuffle_offset = 0x700,
> +};
> +
> +static const struct of_device_id mtk_dramc_of_ids[] = {
> + { .compatible = "mediatek,mt8196-dramc", .data = &dramc_pdata_mt8196 },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mtk_dramc_of_ids);
> +
> +static struct platform_driver mtk_dramc_driver = {
> + .probe = mtk_dramc_probe,
> + .driver = {
> + .name = "mtk-dramc",
> + .of_match_table = mtk_dramc_of_ids,
> + .dev_groups = mtk_dramc_groups,
> + },
> +};
> +module_platform_driver(mtk_dramc_driver);
> +
> +MODULE_AUTHOR("Crystal Guo <crystal.guo@mediatek.com>");
> +MODULE_DESCRIPTION("MediaTek DRAM Controller Driver");
> +MODULE_LICENSE("GPL");
> --
> 2.18.0
>