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[ARM] 4238/1: S3C24XX: docs: update suspend and resume
Remove some of the explicit use of S3C2410 where
it is generic to all the S3C24XX series. Add more
info on the CRC code, and add an example of using
IRQ_EINT0 to resume from suspend
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
authored by Ben Dooks and committed by Russell King 540988eb 1b7b5698
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Documentation/arm/Samsung-S3C24XX/Suspend.txt
+33
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Documentation/arm/Samsung-S3C24XX/Suspend.txt
···
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Introduction
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------------
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The S3C2410 supports a low-power suspend mode, where the SDRAM is kept
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The S3C24XX supports a low-power suspend mode, where the SDRAM is kept
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in Self-Refresh mode, and all but the essential peripheral blocks are
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powered down. For more information on how this works, please look
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at the S3C2410 datasheets from Samsung.
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at the relevant CPU datasheet from Samsung.
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Requirements
···
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Note, the original method of adding an late_initcall() is wrong,
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and will end up initialising all compiled machines' pm init!
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The following is an example of code used for testing wakeup from
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an falling edge on IRQ_EINT0:
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static irqreturn_t button_irq(int irq, void *pw)
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{
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return IRQ_HANDLED;
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}
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statuc void __init machine_init(void)
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{
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...
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request_irq(IRQ_EINT0, button_irq, IRQF_TRIGGER_FALLING,
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"button-irq-eint0", NULL);
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enable_irq_wake(IRQ_EINT0);
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s3c2410_pm_init();
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}
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Debugging
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---------
···
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2) Whilst the pm code itself will attempt to re-enable the UART clocks,
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care should be taken that any external clock sources that the UARTs
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rely on are still enabled at that point.
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3) If any debugging is placed in the resume path, then it must have the
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relevant clocks and peripherals setup before use (ie, bootloader).
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For example, if you transmit a character from the UART, the baud
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rate and uart controls must be setup beforehand.
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Configuration
···
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Allows the entire memory to be checksummed before and after the
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suspend to see if there has been any corruption of the contents.
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Note, the time to calculate the CRC is dependant on the CPU speed
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and the size of memory. For an 64Mbyte RAM area on an 200MHz
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S3C2410, this can take approximately 4 seconds to complete.
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This support requires the CRC32 function to be enabled.
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