linux-kernel - Re: [PATCH v2 2/2] clk: tegra20: Enable lock-status polling for PLLs

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Date:   Fri, 31 Aug 2018 12:29:48 +0300
From:   Peter De Schrijver <pdeschrijver@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>
CC:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, <linux-clk@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] clk: tegra20: Enable lock-status polling for PLLs

On Thu, Aug 30, 2018 at 09:42:10PM +0300, Dmitry Osipenko wrote:
> Currently all PLL's on Tegra20 use a hardcoded delay despite of having
> a lock-status bit. The lock-status polling was disabled ~7 years ago
> because PLLE was failing to lock and was a suspicion that other PLLs
> might be faulty too. Other PLLs are okay, hence enable the lock-status
> polling for them. This reduces delay of any operation that require PLL
> to lock.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
> 
> Changelog:
> 
> v2:	Don't enable polling for PLLE as it known to not being able to lock.
> 

This isn't correct. The lock bit of PLLE can declare lock too early, but the
PLL itself does lock.

>  drivers/clk/tegra/clk-tegra20.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/clk/tegra/clk-tegra20.c b/drivers/clk/tegra/clk-tegra20.c
> index cc857d4d4a86..cfde3745a0db 100644
> --- a/drivers/clk/tegra/clk-tegra20.c
> +++ b/drivers/clk/tegra/clk-tegra20.c
> @@ -298,7 +298,8 @@ static struct tegra_clk_pll_params pll_c_params = {
>  	.lock_enable_bit_idx = PLL_MISC_LOCK_ENABLE,
>  	.lock_delay = 300,
>  	.freq_table = pll_c_freq_table,
> -	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE,
> +	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE |
> +		 TEGRA_PLL_USE_LOCK,
>  };
>  
>  static struct tegra_clk_pll_params pll_m_params = {
> @@ -314,7 +315,8 @@ static struct tegra_clk_pll_params pll_m_params = {
>  	.lock_enable_bit_idx = PLL_MISC_LOCK_ENABLE,
>  	.lock_delay = 300,
>  	.freq_table = pll_m_freq_table,
> -	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE,
> +	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE |
> +		 TEGRA_PLL_USE_LOCK,
>  };
>  
>  static struct tegra_clk_pll_params pll_p_params = {
> @@ -331,7 +333,7 @@ static struct tegra_clk_pll_params pll_p_params = {
>  	.lock_delay = 300,
>  	.freq_table = pll_p_freq_table,
>  	.flags = TEGRA_PLL_FIXED | TEGRA_PLL_HAS_CPCON |
> -		 TEGRA_PLL_HAS_LOCK_ENABLE,
> +		 TEGRA_PLL_HAS_LOCK_ENABLE | TEGRA_PLL_USE_LOCK,
>  	.fixed_rate =  216000000,
>  };
>  
> @@ -348,7 +350,8 @@ static struct tegra_clk_pll_params pll_a_params = {
>  	.lock_enable_bit_idx = PLL_MISC_LOCK_ENABLE,
>  	.lock_delay = 300,
>  	.freq_table = pll_a_freq_table,
> -	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE,
> +	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE |
> +		 TEGRA_PLL_USE_LOCK,
>  };
>  
>  static struct tegra_clk_pll_params pll_d_params = {
> @@ -364,7 +367,8 @@ static struct tegra_clk_pll_params pll_d_params = {
>  	.lock_enable_bit_idx = PLLDU_MISC_LOCK_ENABLE,
>  	.lock_delay = 1000,
>  	.freq_table = pll_d_freq_table,
> -	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE,
> +	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE |
> +		 TEGRA_PLL_USE_LOCK,
>  };
>  
>  static const struct pdiv_map pllu_p[] = {
> @@ -387,7 +391,8 @@ static struct tegra_clk_pll_params pll_u_params = {
>  	.lock_delay = 1000,
>  	.pdiv_tohw = pllu_p,
>  	.freq_table = pll_u_freq_table,
> -	.flags = TEGRA_PLLU | TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE,
> +	.flags = TEGRA_PLLU | TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE |
> +		 TEGRA_PLL_USE_LOCK,
>  };
>  
>  static struct tegra_clk_pll_params pll_x_params = {
> @@ -403,7 +408,8 @@ static struct tegra_clk_pll_params pll_x_params = {
>  	.lock_enable_bit_idx = PLL_MISC_LOCK_ENABLE,
>  	.lock_delay = 300,
>  	.freq_table = pll_x_freq_table,
> -	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE,
> +	.flags = TEGRA_PLL_HAS_CPCON | TEGRA_PLL_HAS_LOCK_ENABLE |
> +		 TEGRA_PLL_USE_LOCK,
>  };
>  
>  static struct tegra_clk_pll_params pll_e_params = {
> -- 
> 2.18.0
>