From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from fllnx210.ext.ti.com ([198.47.19.17]:24974 "EHLO fllnx210.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751151AbdKUHzG (ORCPT ); Tue, 21 Nov 2017 02:55:06 -0500 Subject: Re: [PATCH v2 1/2] PCI: designware-ep: Fix find_first_zero_bit() usage To: Lorenzo Pieralisi , Niklas Cassel References: <20171117150041.30509-1-niklas.cassel@axis.com> <20171117150041.30509-2-niklas.cassel@axis.com> <20171117184337.GA26321@red-moon> CC: Jingoo Han , Joao Pinto , Bjorn Helgaas , Niklas Cassel , , From: Kishon Vijay Abraham I Message-ID: <4376af2c-7e90-f9b4-7f53-65c00de55e90@ti.com> Date: Tue, 21 Nov 2017 13:24:53 +0530 MIME-Version: 1.0 In-Reply-To: <20171117184337.GA26321@red-moon> Content-Type: text/plain; charset="windows-1252" Sender: linux-pci-owner@vger.kernel.org List-ID: Hi Lorenzo, On Saturday 18 November 2017 12:13 AM, Lorenzo Pieralisi wrote: > [+Kishon - please CC him next time] > > On Fri, Nov 17, 2017 at 04:00:40PM +0100, Niklas Cassel wrote: >> find_first_zero_bit()'s parameter 'size' is defined in bits, >> not in bytes. >> >> find_first_zero_bit() was called with size in bytes rather than bits, >> which thus defined a too low upper limit, causing >> dw_pcie_ep_inbound_atu() to assign iatu index #4 to both bar 4 >> and bar 5, which made bar 5 overwrite the settings set by bar 4. >> >> Fix this by using replacing find_first_zero_bit() with ffz(), >> since ffz() only works on a single 'unsigned long' and therefore >> does not need a size argument. >> >> Fixes: f8aed6ec624f ("PCI: dwc: designware: Add EP mode support") >> Signed-off-by: Niklas Cassel >> --- >> drivers/pci/dwc/pcie-designware-ep.c | 6 ++---- >> 1 file changed, 2 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c >> index d53d5f168363..ab9a9e160daf 100644 >> --- a/drivers/pci/dwc/pcie-designware-ep.c >> +++ b/drivers/pci/dwc/pcie-designware-ep.c >> @@ -70,8 +70,7 @@ static int dw_pcie_ep_inbound_atu(struct dw_pcie_ep *ep, enum pci_barno bar, >> u32 free_win; >> struct dw_pcie *pci = to_dw_pcie_from_ep(ep); >> >> - free_win = find_first_zero_bit(&ep->ib_window_map, >> - sizeof(ep->ib_window_map)); >> + free_win = ffz(ep->ib_window_map); > > You fix the bug at hand but code suffers from the same issue since we > should be checking the value against ~0UL first ie if size in bits < > num_ib_windows (that I think it is unlikely anyway but while at it let's > think if we can improve this). > > @Kishon: maybe we should add a static upper size and declare a > static bitmap accordingly (and still use find_first_zero_bit()) ? > > I think the check against ~0UL should be added anyway, let's get > Kishon's opinion before a v3 (if any). Yeah, for both ffz and find_first_zero_bit, the results are undefined if no zero exists. I'm thinking if we should just use find_first_zero_bit(&ep->ib_window_map, ep->num_ib_windows) after checking if there are some '0' bits left. Thanks Kishon