Messages in this thread | | | Subject | Trying to fix radeonfb suspending on IBM Thinkpad T41 | From | Antti Andreimann <> | Date | Sun, 23 Jan 2005 05:25:04 +0200 |
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Dear community!
The aim of this post is to discuss the radeonfb driver power management issues. Enabling this feature dramatically reduces power consumtion during ACPI suspend to ram. I would appriciate comments from people who are more familiar with Radeon HW programming.
Long and boring background -------------------------- I have a beast called IBM ThinkPad T41. Model No. 2373-2FG Since 2.6.9 ACPI suspend to RAM (S3) has been working nicely, but the power consumption during sleep is unacceptably high: the battery will run dry in about 5-6 hours in sleep mode. The root cause of this is the fact that not all hardware is properly turned off. Namely, at least ethernet adapter, USB and most notably graphics accelerator chip (Radeon Mobility M7 LW) remain powered on. Unfortunately current radeonfb driver is hardcoded to do power management only on PPC platform. Volker Braun has some kernels on his page (http://www.sas.upenn.edu/~vbraun/computing/T41/kernel.html) that incorporate his patch to enable PM on other platforms as well. He also owns a T41, but It's a bit different model and those kernels do not resume properly on my laptop: the machine crashes hard on resume. After a few hours of hacking around in radeonfb sources I think I found the problem and fixed it for my hardware. The results are promising: the power consumption during sleep is about 4-5 times lower: 15min ACPI sleep consumes 1100mW/h without radeonfb and only 230mW/h with properly patched radeonfb driver loaded.
A question to anyone familiar with radeon hardware programming -------------------------------------------------------------- The radeonfb driver has a power management implementation that is used on PPC platform (Macintosh laptops ;). The same implementation seems to work fine on some Thinkpads, but crashes on others. In drivers/video/aty/radeon_pm.c resides a function called: radeon_pm_setup_for_suspend. This function has a following section that manages to crash at least my laptop:
/* AGP PLL control */ OUTREG(BUS_CNTL1, INREG(BUS_CNTL1) | BUS_CNTL1__AGPCLK_VALID);
OUTREG(BUS_CNTL1, (INREG(BUS_CNTL1) & ~BUS_CNTL1__MOBILE_PLATFORM_SEL_MASK) | (2<<BUS_CNTL1__MOBILE_PLATFORM_SEL__SHIFT)); // 440BX OUTREG(CRTC_OFFSET_CNTL, (INREG(CRTC_OFFSET_CNTL) & ~CRTC_OFFSET_CNTL__CRTC_STEREO_SYNC_OUT_EN));
clk_pin_cntl &= ~CLK_PIN_CNTL__CG_CLK_TO_OUTPIN; clk_pin_cntl |= CLK_PIN_CNTL__XTALIN_ALWAYS_ONb; OUTPLL( pllCLK_PIN_CNTL, clk_pin_cntl);
It can be seen from the comments that this code is specific to Intel 440BX or similar chipset and this is most probably the reason it manages to crash machines that are based on a different chip.
What exactly does this piece of code do and is it needed after all? My machine seems to work fine without it. If it is needed, is it possible to make it more generic?
-- Antti Andreimann - Security Consultant Using Linux since 1993 Member of ELUG since 29.01.2000 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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