linux-kernel - Re: [PATCH v8 13/21] clk: tegra210: Use fence

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Date:   Sun, 11 Aug 2019 12:16:49 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <tglx@...utronix.de>,
        <jason@...edaemon.net>, <marc.zyngier@....com>,
        <linus.walleij@...aro.org>, <stefan@...er.ch>,
        <mark.rutland@....com>
CC:     <pdeschrijver@...dia.com>, <pgaikwad@...dia.com>,
        <sboyd@...nel.org>, <linux-clk@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>, <jckuo@...dia.com>,
        <josephl@...dia.com>, <talho@...dia.com>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <mperttunen@...dia.com>, <spatra@...dia.com>, <robh+dt@...nel.org>,
        <devicetree@...r.kernel.org>, <rjw@...ysocki.net>,
        <viresh.kumar@...aro.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v8 13/21] clk: tegra210: Use fence_udelay during PLLU init


On 8/11/19 11:02 AM, Dmitry Osipenko wrote:
> 09.08.2019 2:46, Sowjanya Komatineni пишет:
>> This patch uses fence_udelay rather than udelay during PLLU
>> initialization to ensure writes to clock registers happens before
>> waiting for specified delay.
>>
>> Acked-by: Thierry Reding <treding@...dia.com>
>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>> ---
>>   drivers/clk/tegra/clk-tegra210.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/clk/tegra/clk-tegra210.c b/drivers/clk/tegra/clk-tegra210.c
>> index 4721ee030d1c..998bf60b219a 100644
>> --- a/drivers/clk/tegra/clk-tegra210.c
>> +++ b/drivers/clk/tegra/clk-tegra210.c
>> @@ -2841,7 +2841,7 @@ static int tegra210_enable_pllu(void)
>>   	reg = readl_relaxed(clk_base + pllu.params->ext_misc_reg[0]);
>>   	reg &= ~BIT(pllu.params->iddq_bit_idx);
>>   	writel_relaxed(reg, clk_base + pllu.params->ext_misc_reg[0]);
>> -	udelay(5);
>> +	fence_udelay(5, clk_base);
>>   
>>   	reg = readl_relaxed(clk_base + PLLU_BASE);
>>   	reg &= ~GENMASK(20, 0);
>> @@ -2849,7 +2849,7 @@ static int tegra210_enable_pllu(void)
>>   	reg |= fentry->n << 8;
>>   	reg |= fentry->p << 16;
>>   	writel(reg, clk_base + PLLU_BASE);
>> -	udelay(1);
>> +	fence_udelay(1, clk_base);
>>   	reg |= PLL_ENABLE;
>>   	writel(reg, clk_base + PLLU_BASE);
>>   
>> @@ -2895,12 +2895,12 @@ static int tegra210_init_pllu(void)
>>   		reg = readl_relaxed(clk_base + XUSB_PLL_CFG0);
>>   		reg &= ~XUSB_PLL_CFG0_PLLU_LOCK_DLY_MASK;
>>   		writel_relaxed(reg, clk_base + XUSB_PLL_CFG0);
>> -		udelay(1);
>> +		fence_udelay(1, clk_base);
>>   
>>   		reg = readl_relaxed(clk_base + PLLU_HW_PWRDN_CFG0);
>>   		reg |= PLLU_HW_PWRDN_CFG0_SEQ_ENABLE;
>>   		writel_relaxed(reg, clk_base + PLLU_HW_PWRDN_CFG0);
>> -		udelay(1);
>> +		fence_udelay(1, clk_base);
>>   
>>   		reg = readl_relaxed(clk_base + PLLU_BASE);
>>   		reg &= ~PLLU_BASE_CLKENABLE_USB;
>>
> The clk_base corresponds to the RESET controller's part of Clock-and-Reset hardware, is it
> okay to read-back the RST register and not the clock for the fencing?
Yes as both reset and clocks are all in same CAR