Re: [PATCH v7 05/16] clk: tegra: Add DFLL DVCO reset control for Tegra124

Peter De Schrijver
2015-02-12T14:19:44Z

On Thu, Jan 08, 2015 at 03:22:08PM +0200, Mikko Perttunen wrote:
> From: Paul Walmsley <pwalmsley@nvidia.com>
>
> The DVCO present in the DFLL IP block has a separate reset line,
> exposed via the CAR IP block. This reset line is asserted upon SoC
> reset. Unless something (such as the DFLL driver) deasserts this
> line, the DVCO will not oscillate, although reads and writes to the
> DFLL IP block will complete.
>
> Thanks to Aleksandr Frid <afrid@nvidia.com> for identifying this and
> saving hours of debugging time.
>

Should this be done as a reset driver?

> Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
> [ttynkkynen: ported to tegra124 from tegra114]
> Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
> Signed-off-by: Mikko Perttunen <mikko.perttunen@kapsi.fi>
> ---
> drivers/clk/tegra/clk-tegra124.c | 47 ++++++++++++++++++++++++++++++++++++++++
> drivers/clk/tegra/clk.h | 3 +++
> 2 files changed, 50 insertions(+)
>
> diff --git a/drivers/clk/tegra/clk-tegra124.c b/drivers/clk/tegra/clk-tegra124.c
> index f5f9bac..623b77f 100644
> --- a/drivers/clk/tegra/clk-tegra124.c
> +++ b/drivers/clk/tegra/clk-tegra124.c
> @@ -31,6 +31,9 @@
> #define CLK_SOURCE_CSITE 0x1d4
> #define CLK_SOURCE_EMC 0x19c
>
> +#define RST_DFLL_DVCO 0x2f4
> +#define DVFS_DFLL_RESET_SHIFT 0
> +
> #define PLLC_BASE 0x80
> #define PLLC_OUT 0x84
> #define PLLC_MISC2 0x88
> @@ -1399,6 +1402,50 @@ static void __init tegra124_clock_apply_init_table(void)
> tegra_init_from_table(init_table, clks, TEGRA124_CLK_CLK_MAX);
> }
>
> +/**
> + * tegra124_car_barrier - wait for pending writes to the CAR to complete
> + *
> + * Wait for any outstanding writes to the CAR MMIO space from this CPU
> + * to complete before continuing execution. No return value.
> + */
> +static void tegra124_car_barrier(void)
> +{
> + readl_relaxed(clk_base + RST_DFLL_DVCO);
> +}
> +
> +/**
> + * tegra124_clock_assert_dfll_dvco_reset - assert the DFLL's DVCO reset
> + *
> + * Assert the reset line of the DFLL's DVCO. No return value.
> + */
> +void tegra124_clock_assert_dfll_dvco_reset(void)
> +{
> + u32 v;
> +
> + v = readl_relaxed(clk_base + RST_DFLL_DVCO);
> + v |= (1 << DVFS_DFLL_RESET_SHIFT);
> + writel_relaxed(v, clk_base + RST_DFLL_DVCO);
> + tegra124_car_barrier();
> +}
> +EXPORT_SYMBOL(tegra124_clock_assert_dfll_dvco_reset);
> +
> +/**
> + * tegra124_clock_deassert_dfll_dvco_reset - deassert the DFLL's DVCO reset
> + *
> + * Deassert the reset line of the DFLL's DVCO, allowing the DVCO to
> + * operate. No return value.
> + */
> +void tegra124_clock_deassert_dfll_dvco_reset(void)
> +{
> + u32 v;
> +
> + v = readl_relaxed(clk_base + RST_DFLL_DVCO);
> + v &= ~(1 << DVFS_DFLL_RESET_SHIFT);
> + writel_relaxed(v, clk_base + RST_DFLL_DVCO);
> + tegra124_car_barrier();
> +}
> +EXPORT_SYMBOL(tegra124_clock_deassert_dfll_dvco_reset);
> +
> static void __init tegra124_clock_init(struct device_node *np)
> {
> struct device_node *node;
> diff --git a/drivers/clk/tegra/clk.h b/drivers/clk/tegra/clk.h
> index 4e458aa..def0ea4 100644
> --- a/drivers/clk/tegra/clk.h
> +++ b/drivers/clk/tegra/clk.h
> @@ -629,6 +629,9 @@ void tegra114_clock_tune_cpu_trimmers_init(void);
> void tegra114_clock_assert_dfll_dvco_reset(void);
> void tegra114_clock_deassert_dfll_dvco_reset(void);
>
> +void tegra124_clock_assert_dfll_dvco_reset(void);
> +void tegra124_clock_deassert_dfll_dvco_reset(void);
> +
> typedef void (*tegra_clk_apply_init_table_func)(void);
> extern tegra_clk_apply_init_table_func tegra_clk_apply_init_table;
>
> --
> 2.2.1
>