Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751847Ab1CJKGf (ORCPT ); Thu, 10 Mar 2011 05:06:35 -0500 Received: from smarthost1.greenhost.nl ([195.190.28.78]:61000 "EHLO smarthost1.greenhost.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751379Ab1CJKGd (ORCPT ); Thu, 10 Mar 2011 05:06:33 -0500 Message-ID: In-Reply-To: References: <20110216192658.GA7225@blimp.localdomain> <20110217221329.GA3332@x61.home> <3f792aaf90cf0b3d49be21baa2682d5d.squirrel@webmail.greenhost.nl> <20110222130440.21a27714@jbarnes-desktop> <20110222223120.GA3567@x61.home> <3e6f092bd0aa54fd6b9eb524f6c87ecf.squirrel@webmail.greenhost.nl> <1a06e2711df021a802d609ad1a75db17.squirrel@webmail.greenhost.nl> Date: Thu, 10 Mar 2011 11:06:28 +0100 (CET) Subject: Re: [PATCH] fix backlight brightness on intel LVDS panel after reopening lid From: "Indan Zupancic" To: "Takashi Iwai" Cc: "Linus Torvalds" , "Alex Riesen" , "Jesse Barnes" , "DRI mailing list" , "Chris Wilson" , "Linux Kernel Mailing List" , "Tino Keitel" , stable@kernel.org User-Agent: SquirrelMail/1.4.17 MIME-Version: 1.0 Content-Type: text/plain;charset=UTF-8 Content-Transfer-Encoding: 8bit X-Priority: 3 (Normal) Importance: Normal X-Spam-Score: 0.1 X-Scan-Signature: 9bf25e62613229f0beb95d8bfda7a7aa Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6139 Lines: 178 On Thu, March 10, 2011 09:25, Takashi Iwai wrote: > At Thu, 10 Mar 2011 08:49:37 +0100, > Takashi Iwai wrote: >> >> At Thu, 10 Mar 2011 06:50:09 +0100 (CET), >> Indan Zupancic wrote: >> > >> > Hello, >> > >> > On Fri, March 4, 2011 19:47, Linus Torvalds wrote: >> > > Alex, can you confirm that the revert of 951f3512dba5 plus the >> > > one-liner patch from Takashi that Indan quoted also works for you? >> > > >> > > Linus >> > > >> > > On Thu, Mar 3, 2011 at 10:53 PM, Indan Zupancic wrote: >> > >> >> > >> So please revert my patch and apply Takashi Iwai's, which fixes the >> > >> most immediate bug without changing anything else. This should go >> > >> in stable too. >> > > >> > >> > I found another backlight bug: >> > >> > When suspending intel_panel_disable_backlight() is never called, >> > but intel_panel_enable_backlight() is called at resume. With the >> > effect that if the brightness was ever changed after screen >> > blanking, the wrong brightness gets restored. >> > >> > This explains the weird behaviour I've seen. I didn't see it with >> > combination mode, because then the brightness is always the same >> > (zero or the maximum, the BIOS only uses LBPC on my system.) I'll >> > send a patch in a moment. >> > >> > Alternative for reverting the combination mode removal (I can also >> > redo the patch against the revert and Takashi's patch, if that's >> > preferred): >> > >> > -- >> > >> > drm/i915: Do handle backlight combination mode specially >> > >> > Add back the combination mode check, but with slightly cleaner code >> > and the weirdness removed: No val >>= 1, but also no val &= ~1. The >> > old code probably confused bit 0 with BLM_LEGACY_MODE, which is bit 16. >> > The other change is clearer calculations: Just check for zero level >> > explicitly instead of avoiding the divide-by-zero. >> > >> > Signed-off-by: Indan Zupancic >> > >> > --- >> > >> > diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c >> > index d860abe..b05631a 100644 >> > --- a/drivers/gpu/drm/i915/intel_panel.c >> > +++ b/drivers/gpu/drm/i915/intel_panel.c >> > @@ -30,6 +30,10 @@ >> > >> > #include "intel_drv.h" >> > >> > +#define PCI_LBPC 0xf4 /* legacy/combination backlight modes */ >> > +#define BLM_COMBINATION_MODE (1 << 30) >> > +#define BLM_LEGACY_MODE (1 << 16) >> > + >> > void >> > intel_fixed_panel_mode(struct drm_display_mode *fixed_mode, >> > struct drm_display_mode *adjusted_mode) >> > @@ -110,6 +114,22 @@ done: >> > dev_priv->pch_pf_size = (width << 16) | height; >> > } >> > >> > +/* >> > + * What about gen 3? If there are no gen 3 systems with ASLE, >> > + * then it doesn't matter, as we don't need to change the >> > + * brightness. But then the gen 2 check can be removed too. >> > + */ >> > +static int is_backlight_combination_mode(struct drm_device *dev) >> > +{ >> > + struct drm_i915_private *dev_priv = dev->dev_private; >> > + >> > + if (INTEL_INFO(dev)->gen >= 4) >> > + return I915_READ(BLC_PWM_CTL2) & BLM_COMBINATION_MODE; >> > + if (IS_GEN2(dev)) >> > + return I915_READ(BLC_PWM_CTL) & BLM_LEGACY_MODE; >> > + return 0; >> > +} >> > + >> > static u32 i915_read_blc_pwm_ctl(struct drm_i915_private *dev_priv) >> > { >> > u32 val; >> > @@ -163,9 +183,12 @@ u32 intel_panel_get_max_backlight(struct drm_device *dev) >> > max >>= 17; >> > } else { >> > max >>= 16; >> > + /* Ignore BLM_LEGACY_MODE bit */ >> > if (INTEL_INFO(dev)->gen < 4) >> > max &= ~1; >> > } >> > + if (is_backlight_combination_mode(dev)) >> > + max *= 0xff; >> > } >> > >> > DRM_DEBUG_DRIVER("max backlight PWM = %d\n", max); >> > @@ -183,6 +206,12 @@ u32 intel_panel_get_backlight(struct drm_device *dev) >> > val = I915_READ(BLC_PWM_CTL) & BACKLIGHT_DUTY_CYCLE_MASK; >> > if (IS_PINEVIEW(dev)) >> > val >>= 1; >> > + if (is_backlight_combination_mode(dev)){ >> > + u8 lbpc; >> > + >> > + pci_read_config_byte(dev->pdev, PCI_LBPC, &lbpc); >> > + val *= lbpc; >> > + } >> > } >> > >> > DRM_DEBUG_DRIVER("get backlight PWM = %d\n", val); >> > @@ -205,6 +234,15 @@ void intel_panel_set_backlight(struct drm_device *dev, u32 level) >> > >> > if (HAS_PCH_SPLIT(dev)) >> > return intel_pch_panel_set_backlight(dev, level); >> > + >> > + if (level && is_backlight_combination_mode(dev)){ >> > + u32 max = intel_panel_get_max_backlight(dev); >> > + u8 lpbc; >> > + >> > + lpbc = level * 0xff / max; >> > + level /= lpbc; >> >> Hmm, I don't think this calculation is correct. This would result >> in level of opregion over its limit. For example, assume the level >> max = 100, so total max = 25500. Passing level=150 here will be: >> >> lbpc = 150 * 0xff / 25500 = 1.5 = 1 >> level = 150 / 1 = 150, which is over limit. >> >> More worse, lbpc can be zero when level is below 100 in the case >> above... > > That is, Chris' original code in that portion was correct: > > if (is_backlight_combination_mode(dev)){ > u32 max = intel_panel_get_max_backlight(dev); > u8 lpbc; > > lpbc = level * 0xfe / max + 1; > level /= lpbc; > pci_write_config_byte(dev->pdev, PCI_LBPC, lpbc); > } > > This will fit within the right range. > Though, changing like below will give a bit better calculation, > closer to the real level. > > lpbc = level * 0xfe / max + 1; > level = (level + lpbc / 2) / lpbc; Indeed, though I don't think it makes much difference in practise. All in all it seems best to just revert my patch and apply your fix. Any "improvements" I may have are either buggy or can be added later. Care to make a new patch with the above improvement added? You can add my acked-by, for what it's worth. At this point I don't even dare removing that "obviously" bogus val &= ~1; I bet it's an undocumented bit having some obscure secret function on not well tested systems. Greetings, Indan -- 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/