From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:36551 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751629AbcFCXEQ (ORCPT ); Fri, 3 Jun 2016 19:04:16 -0400 Received: by mail-wm0-f67.google.com with SMTP id m124so1374887wme.3 for ; Fri, 03 Jun 2016 16:04:15 -0700 (PDT) Date: Sat, 4 Jun 2016 01:00:45 +0200 From: Daniel Vetter To: Stefan Agner Cc: airlied@linux.ie, dri-devel@lists.freedesktop.org, jianwei.wang.chn@gmail.com, meng.yi@nxp.com, alison.wang@freescale.com, Mark Brown , stable@vger.kernel.org, alexander.stein@systec-electronic.com Subject: Re: [PATCH] drm/fsl-dcu: use flat regmap cache Message-ID: <20160603230045.GA14529@phenom.ffwll.local> References: <1464993799-2098-1-git-send-email-stefan@agner.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1464993799-2098-1-git-send-email-stefan@agner.ch> Sender: stable-owner@vger.kernel.org List-ID: On Fri, Jun 03, 2016 at 03:43:19PM -0700, Stefan Agner wrote: > Using flat regmap cache instead of RB-tree to avoid the following > lockdep warning on driver load: > WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:2755 lockdep_trace_alloc+0x15c/0x160() > DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)) > > The RB-tree regmap cache needs to allocate new space on first > writes. However, allocations in an atomic context (e.g. when a > spinlock is held) are not allowed. The function regmap_write > calls map->lock, which acquires a spinlock in the fast_io case. > Since the FSL DCU driver uses MMIO, the regmap bus of type > regmap_mmio is being used which has fast_io set to true. > > Use flat regmap cache and specify max register to be large > enouth to cover all registers available in LS1021a and Vybrids > register space. > > Signed-off-by: Stefan Agner > Cc: Mark Brown > Cc: stable@vger.kernel.org > --- > While regmap cache is used for suspend/resume only (which is > broken in its current state) Mark noted that using the RB regmap > cache can also cause issues during initialization of the driver. > This patch migrates to flat regmap cache (which we can also use > to fix the issue in stable kernels), and yet another patchset > moves to the atomic suspend/resume helpers (which will not go > into stable...) While talking suspend/resume, I highly recommend drm_atomic_helper_suspend and drm_atomic_helper_resume. In my experience dumb safe/restore of registers for restoring modeset state leads to tears. -Daniel > > Dave, I saw that you just sent out the pull for rc2, will send > a pull request for rc3 early next week... > > -- > Stefan > > drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c > index 0ec1ad9..dc723f7 100644 > --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c > +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c > @@ -42,9 +42,10 @@ static const struct regmap_config fsl_dcu_regmap_config = { > .reg_bits = 32, > .reg_stride = 4, > .val_bits = 32, > - .cache_type = REGCACHE_RBTREE, > + .cache_type = REGCACHE_FLAT, > > .volatile_reg = fsl_dcu_drm_is_volatile_reg, > + .max_register = 0x11fc, > }; > > static int fsl_dcu_drm_irq_init(struct drm_device *dev) > -- > 2.8.2 > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch