From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758524AbcDETK2 (ORCPT ); Tue, 5 Apr 2016 15:10:28 -0400 Received: from gloria.sntech.de ([95.129.55.99]:52111 "EHLO gloria.sntech.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751712AbcDETK1 (ORCPT ); Tue, 5 Apr 2016 15:10:27 -0400 From: Heiko Stuebner To: John Keeping Cc: Joerg Roedel , iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, Tomeu Vizoso Subject: Re: [PATCH] iommu/rockchip: Fix "is stall active" check Date: Tue, 05 Apr 2016 12:10:05 -0700 Message-ID: <9799340.GJHE2cZK7r@phil> User-Agent: KMail/4.14.10 (Linux/4.3.0-1-amd64; KDE/4.14.14; x86_64; ; ) In-Reply-To: <20160405182858.382ea465.john@metanate.com> References: <1459865146-25308-1-git-send-email-john@metanate.com> <5389576.zuTxjFsmO4@phil> <20160405182858.382ea465.john@metanate.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Dienstag, 5. April 2016, 18:28:58 schrieb John Keeping: > On Tue, 05 Apr 2016 10:21:27 -0700, Heiko Stuebner wrote: > > Am Dienstag, 5. April 2016, 15:05:46 schrieb John Keeping: > > > Since commit cd6438c5f844 ("iommu/rockchip: Reconstruct to support > > > multi > > > slaves") rk_iommu_is_stall_active() always returns false because the > > > bitwise AND operates on the boolean flag promoted to an integer and a > > > value that is either zero or BIT(2). > > > > > > Explicitly convert the right-hand value to a boolean so that both > > > sides > > > are guaranteed to be either zero or one. > > > > > > rk_iommu_is_paging_enabled() does not suffer from the same problem > > > since > > > RK_MMU_STATUS_PAGING_ENABLED is BIT(0), but let's apply the same > > > change > > > for consistency and to make it clear that it's correct without needing > > > to lookup the value. > > > > > > Fixes: cd6438c5f844 ("iommu/rockchip: Reconstruct to support multi > > > slaves") Signed-off-by: John Keeping > > > > Nice catch, thanks. > > > > Reviewed-by: Heiko Stuebner > > > > John, out of curiosity, how did you find that problem? Excess stall > > error > > messages or something else? > > I was testing the drm iommu patches I posted today [1] and noticed an > "Enable stall request timed out" error when unbinding the > display-subsystem, but the RK_MMU_STATUS value printed in the error > message indicated that stall active was set. > > [1] http://article.gmane.org/gmane.comp.video.dri.devel/150721 So it seems both you and Tomeu were working to resolve the same issue [2]. And John's patch seems to actually fix the underlying problem. [2] https://lkml.org/lkml/2016/3/22/493 > > > --- > > > > > > drivers/iommu/rockchip-iommu.c | 8 ++++---- > > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > > > diff --git a/drivers/iommu/rockchip-iommu.c > > > b/drivers/iommu/rockchip-iommu.c index a6f593a0a29e..5710a06c3049 > > > 100644 > > > --- a/drivers/iommu/rockchip-iommu.c > > > +++ b/drivers/iommu/rockchip-iommu.c > > > @@ -315,8 +315,8 @@ static bool rk_iommu_is_stall_active(struct > > > rk_iommu > > > *iommu) int i; > > > > > > for (i = 0; i < iommu->num_mmu; i++) > > > > > > - active &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) & > > > - RK_MMU_STATUS_STALL_ACTIVE; > > > + active &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) & > > > + RK_MMU_STATUS_STALL_ACTIVE); > > > > > > return active; > > > > > > } > > > > > > @@ -327,8 +327,8 @@ static bool rk_iommu_is_paging_enabled(struct > > > rk_iommu *iommu) int i; > > > > > > for (i = 0; i < iommu->num_mmu; i++) > > > > > > - enable &= rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) & > > > - RK_MMU_STATUS_PAGING_ENABLED; > > > + enable &= !!(rk_iommu_read(iommu->bases[i], RK_MMU_STATUS) & > > > + RK_MMU_STATUS_PAGING_ENABLED); > > > > > > return enable; > > > > > > }