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https://github.com/CTCaer/switch-l4t-atf.git
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540a5ba8d9
This patch fixes several issues with the SP804 delay timer on FVP:
* By default, the SP804 dual timer on FVP runs at 32 KHz. In order
to run the timer at 35 MHz (as specified in the FVP user manual)
the Overwrite bit in the SP810 control register must be set.
* The CLKMULT and CLKDIV definitions are mixed up:
delta(us) = delta(ticks) * T(us) = delta(ticks) / f(MHz)
From the delay function:
delta_us = (delta * ops->clk_mult) / ops->clk_div;
Matching both expressions:
1 / f(MHz) = ops->clk_mult / ops->clk_div
And consequently:
f(MHz) = ops->clk_div / ops->clk_mult
Which, for a 35 MHz timer, translates to:
ops->clk_div = 35
ops->clk_mult = 1
* The comment in the delay timer header file has been corrected:
The ratio of the multiplier and the divider is the clock period
in microseconds, not the frequency.
Change-Id: Iffd5ce0a5a28fa47c0720c0336d81b678ff8fdf1
56 lines
2.3 KiB
C
56 lines
2.3 KiB
C
/*
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* Copyright (c) 2015, ARM Limited and Contributors. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* Neither the name of ARM nor the names of its contributors may be used
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* to endorse or promote products derived from this software without specific
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* prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __DELAY_TIMER_H__
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#define __DELAY_TIMER_H__
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#include <stdint.h>
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/********************************************************************
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* A simple timer driver providing synchronous delay functionality.
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* The driver must be initialized with a structure that provides a
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* function pointer to return the timer value and a clock
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* multiplier/divider. The ratio of the multiplier and the divider is
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* the clock period in microseconds.
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********************************************************************/
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typedef struct timer_ops {
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uint32_t (*get_timer_value)(void);
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uint32_t clk_mult;
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uint32_t clk_div;
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} timer_ops_t;
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void mdelay(uint32_t msec);
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void udelay(uint32_t usec);
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void timer_init(const timer_ops_t *ops);
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#endif /* __DELAY_TIMER_H__ */
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