viafb: don't touch clock state on OLPC XO-1.5 (012a1211) · Commits · 戴 / test

As detailed in the thread titled "viafb PLL/clock tweaking causes XO-1.5 instability," enabling or disabling the IGA1/IGA2 clocks causes occasional stability problems during suspend/resume cycles on this platform. This is rather odd, as the documentation suggests that clocks have two states (on/off) and the default (stable) configuration is configured to enable the clock only when it is needed. However, explicitly enabling *or* disabling the clock triggers this system instability, suggesting that there is a 3rd state at play here. Leaving the clock enable/disable registers alone solves this problem. This fixes spurious reboots during suspend/resume behaviour introduced by commit . Signed-off-by:

Daniel Drake <dsd@laptop.org> Signed-off-by:

Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Cc: stable@vger.kernel.org

drivers/video/via/via_clock.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -25,6 +25,7 @@

		#include <linux/kernel.h>
		#include <linux/via-core.h>
		#include <asm/olpc.h>
		#include "via_clock.h"
		#include "global.h"
		#include "debug.h"
		@@ -289,6 +290,10 @@ static void dummy_set_pll(struct via_pll_config config)
		printk(KERN_INFO "Using undocumented set PLL.\n%s", via_slap);
		}

		static void noop_set_clock_state(u8 state)
		{
		}

		void via_clock_init(struct via_clock *clock, int gfx_chip)
		{
		switch (gfx_chip) {
		@@ -346,4 +351,18 @@ void via_clock_init(struct via_clock *clock, int gfx_chip)
		break;

		}

		if (machine_is_olpc()) {
		/* The OLPC XO-1.5 cannot suspend/resume reliably if the
		* IGA1/IGA2 clocks are set as on or off (memory rot
		* occasionally happens during suspend under such
		* configurations).
		*
		* The only known stable scenario is to leave this bits as-is,
		* which in their default states are documented to enable the
		* clock only when it is needed.
		*/
		clock->set_primary_clock_state = noop_set_clock_state;
		clock->set_secondary_clock_state = noop_set_clock_state;
		}
		}

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