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Date: Thu, 13 Jun 2019 13:49:45 +0300
From: Peter De Schrijver <pdeschrijver@...dia.com>
To: Dmitry Osipenko <digetx@...il.com>
CC: Rob Herring <robh+dt@...nel.org>,
Michael Turquette <mturquette@...libre.com>,
Joseph Lo <josephl@...dia.com>,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>,
"Prashant Gaikwad" <pgaikwad@...dia.com>,
<devicetree@...r.kernel.org>, <linux-clk@...r.kernel.org>,
<linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/8] clk: tegra20/30: Add custom EMC clock
implementation
On Fri, May 24, 2019 at 08:23:46PM +0300, Dmitry Osipenko wrote:
> A proper External Memory Controller clock rounding and parent selection
> functionality is required by the EMC drivers. It is not available using
> the generic clock implementation, hence add a custom one. The clock rate
> rounding shall be done by the EMC drivers because they have information
> about available memory timings, so the drivers will have to register a
> callback that will round the requested rate. EMC clock users won't be able
> to request EMC clock by getting -EPROBE_DEFER until EMC driver is probed
> and the callback is set up. The functionality is somewhat similar to the
> clk-emc.c which serves Tegra124+ SoC's, the later HW generations support
> more parent clock sources and the HW configuration and integration with
> the EMC drivers differs a tad from the older gens, hence it's not really
> worth to try to squash everything into a single source file.
>
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
> drivers/clk/tegra/Makefile | 2 +
> drivers/clk/tegra/clk-tegra20-emc.c | 299 ++++++++++++++++++++++++++++
> drivers/clk/tegra/clk-tegra20.c | 55 ++---
> drivers/clk/tegra/clk-tegra30.c | 38 +++-
> drivers/clk/tegra/clk.h | 6 +
> include/linux/clk/tegra.h | 14 ++
> 6 files changed, 362 insertions(+), 52 deletions(-)
> create mode 100644 drivers/clk/tegra/clk-tegra20-emc.c
>
> diff --git a/drivers/clk/tegra/Makefile b/drivers/clk/tegra/Makefile
> index 4812e45c2214..df966ca06788 100644
> --- a/drivers/clk/tegra/Makefile
> +++ b/drivers/clk/tegra/Makefile
> @@ -17,7 +17,9 @@ obj-y += clk-tegra-fixed.o
> obj-y += clk-tegra-super-gen4.o
> obj-$(CONFIG_TEGRA_CLK_EMC) += clk-emc.o
> obj-$(CONFIG_ARCH_TEGRA_2x_SOC) += clk-tegra20.o
> +obj-$(CONFIG_ARCH_TEGRA_2x_SOC) += clk-tegra20-emc.o
> obj-$(CONFIG_ARCH_TEGRA_3x_SOC) += clk-tegra30.o
> +obj-$(CONFIG_ARCH_TEGRA_3x_SOC) += clk-tegra20-emc.o
> obj-$(CONFIG_ARCH_TEGRA_114_SOC) += clk-tegra114.o
> obj-$(CONFIG_ARCH_TEGRA_124_SOC) += clk-tegra124.o
> obj-$(CONFIG_TEGRA_CLK_DFLL) += clk-tegra124-dfll-fcpu.o
> diff --git a/drivers/clk/tegra/clk-tegra20-emc.c b/drivers/clk/tegra/clk-tegra20-emc.c
> new file mode 100644
> index 000000000000..d971b5425ce3
> --- /dev/null
> +++ b/drivers/clk/tegra/clk-tegra20-emc.c
> @@ -0,0 +1,299 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bits.h>
> +#include <linux/clk-provider.h>
> +#include <linux/clk/tegra.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +
> +#include "clk.h"
> +
> +#define CLK_SOURCE_EMC_2X_CLK_DIVISOR_MASK GENMASK(7, 0)
> +#define CLK_SOURCE_EMC_2X_CLK_SRC_MASK GENMASK(31, 30)
> +#define CLK_SOURCE_EMC_2X_CLK_SRC_SHIFT 30
> +
> +#define MC_EMC_SAME_FREQ BIT(16)
> +#define USE_PLLM_UD BIT(29)
> +
> +#define EMC_SRC_PLL_M 0
> +#define EMC_SRC_PLL_C 1
> +#define EMC_SRC_PLL_P 2
> +#define EMC_SRC_CLK_M 3
> +
> +static const char * const emc_parent_clk_names[] = {
> + "pll_m", "pll_c", "pll_p", "clk_m",
> +};
> +
> +struct tegra_clk_emc {
> + struct clk_hw hw;
> + void __iomem *reg;
> + bool mc_same_freq;
> + bool want_low_jitter;
> +
> + tegra20_clk_emc_round_cb *round_cb;
> + void *cb_arg;
> +};
> +
> +static inline struct tegra_clk_emc *to_tegra_clk_emc(struct clk_hw *hw)
> +{
> + return container_of(hw, struct tegra_clk_emc, hw);
> +}
> +
> +static unsigned long emc_recalc_rate(struct clk_hw *hw,
> + unsigned long parent_rate)
> +{
> + struct tegra_clk_emc *emc = to_tegra_clk_emc(hw);
> + u32 val, div;
> +
> + val = readl_relaxed(emc->reg);
> + div = val & CLK_SOURCE_EMC_2X_CLK_DIVISOR_MASK;
> +
> + return DIV_ROUND_UP(parent_rate * 2, div + 2);
> +}
> +
> +static u8 emc_get_parent(struct clk_hw *hw)
> +{
> + struct tegra_clk_emc *emc = to_tegra_clk_emc(hw);
> +
> + return readl_relaxed(emc->reg) >> CLK_SOURCE_EMC_2X_CLK_SRC_SHIFT;
> +}
> +
> +static int emc_set_parent(struct clk_hw *hw, u8 index)
> +{
> + struct tegra_clk_emc *emc = to_tegra_clk_emc(hw);
> + u32 val, div;
> +
> + val = readl_relaxed(emc->reg);
> + val &= ~CLK_SOURCE_EMC_2X_CLK_SRC_MASK;
> + val |= index << CLK_SOURCE_EMC_2X_CLK_SRC_SHIFT;
> +
> + div = val & CLK_SOURCE_EMC_2X_CLK_DIVISOR_MASK;
> +
> + if (index == EMC_SRC_PLL_M && div == 0 && emc->want_low_jitter)
> + val |= USE_PLLM_UD;
> + else
> + val &= ~USE_PLLM_UD;
> +
> + if (emc->mc_same_freq)
> + val |= MC_EMC_SAME_FREQ;
> + else
> + val &= ~MC_EMC_SAME_FREQ;
> +
> + writel_relaxed(val, emc->reg);
> +
I think technically you need a fence_udelay(1) here, but in practice
this is probably not needed because you will poll some EMC register for
the frequency completion anyway. Maybe add a comment about this?
> + return 0;
> +}
> +
> +static int emc_set_rate(struct clk_hw *hw, unsigned long rate,
> + unsigned long parent_rate)
> +{
> + struct tegra_clk_emc *emc = to_tegra_clk_emc(hw);
> + unsigned int index;
> + u32 val, div;
> +
> + div = div_frac_get(rate, parent_rate, 8, 1, 0);
> +
> + val = readl_relaxed(emc->reg);
> + val &= ~CLK_SOURCE_EMC_2X_CLK_DIVISOR_MASK;
> + val |= div;
> +
> + index = val >> CLK_SOURCE_EMC_2X_CLK_SRC_SHIFT;
> +
> + if (index == EMC_SRC_PLL_M && div == 0 && emc->want_low_jitter)
> + val |= USE_PLLM_UD;
> + else
> + val &= ~USE_PLLM_UD;
> +
> + if (emc->mc_same_freq)
> + val |= MC_EMC_SAME_FREQ;
> + else
> + val &= ~MC_EMC_SAME_FREQ;
> +
> + writel_relaxed(val, emc->reg);
> +
Same here.
> + return 0;
> +}
> +
> +static int emc_set_rate_and_parent(struct clk_hw *hw,
> + unsigned long rate,
> + unsigned long parent_rate,
> + u8 index)
> +{
> + struct tegra_clk_emc *emc = to_tegra_clk_emc(hw);
> + u32 val, div;
> +
> + div = div_frac_get(rate, parent_rate, 8, 1, 0);
> +
> + val = readl_relaxed(emc->reg);
> +
> + val &= ~CLK_SOURCE_EMC_2X_CLK_SRC_MASK;
> + val |= index << CLK_SOURCE_EMC_2X_CLK_SRC_SHIFT;
> +
> + val &= ~CLK_SOURCE_EMC_2X_CLK_DIVISOR_MASK;
> + val |= div;
> +
> + if (index == EMC_SRC_PLL_M && div == 0 && emc->want_low_jitter)
> + val |= USE_PLLM_UD;
> + else
> + val &= ~USE_PLLM_UD;
> +
> + if (emc->mc_same_freq)
> + val |= MC_EMC_SAME_FREQ;
> + else
> + val &= ~MC_EMC_SAME_FREQ;
> +
> + writel_relaxed(val, emc->reg);
> +
And here.
> + return 0;
> +}
Peter.
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