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Date: Tue, 14 Dec 2021 06:17:08 +0000 From: Pkshih <pkshih@...ltek.com> To: Kai-Heng Feng <kai.heng.feng@...onical.com> CC: "tony0620emma@...il.com" <tony0620emma@...il.com>, "jian-hong@...lessm.com" <jhp@...lessos.org>, Kalle Valo <kvalo@...eaurora.org>, "David S. Miller" <davem@...emloft.net>, "Jakub Kicinski" <kuba@...nel.org>, Bernie Huang <phhuang@...ltek.com>, Brian Norris <briannorris@...omium.org>, "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org> Subject: RE: [PATCH v2] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE > -----Original Message----- > From: Kai-Heng Feng <kai.heng.feng@...onical.com> > Sent: Tuesday, December 14, 2021 2:07 PM > To: Pkshih <pkshih@...ltek.com> > Cc: tony0620emma@...il.com; jian-hong@...lessm.com <jhp@...lessos.org>; Kalle Valo <kvalo@...eaurora.org>; > David S. Miller <davem@...emloft.net>; Jakub Kicinski <kuba@...nel.org>; Bernie Huang > <phhuang@...ltek.com>; Brian Norris <briannorris@...omium.org>; linux-wireless@...r.kernel.org; > netdev@...r.kernel.org; linux-kernel@...r.kernel.org > Subject: Re: [PATCH v2] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE > > On Tue, Dec 14, 2021 at 1:59 PM Pkshih <pkshih@...ltek.com> wrote: > > > > > > > -----Original Message----- > > > From: Kai-Heng Feng <kai.heng.feng@...onical.com> > > > Sent: Tuesday, December 14, 2021 1:33 PM > > > To: tony0620emma@...il.com; Pkshih <pkshih@...ltek.com> > > > Cc: jian-hong@...lessm.com; Kai-Heng Feng <kai.heng.feng@...onical.com>; Kalle Valo > > > <kvalo@...eaurora.org>; David S. Miller <davem@...emloft.net>; Jakub Kicinski <kuba@...nel.org>; Bernie > > > Huang <phhuang@...ltek.com>; Brian Norris <briannorris@...omium.org>; linux-wireless@...r.kernel.org; > > > netdev@...r.kernel.org; linux-kernel@...r.kernel.org > > > Subject: [PATCH v2] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE > > > > > > Many Intel based platforms face system random freeze after commit > > > 9e2fd29864c5 ("rtw88: add napi support"). > > > > > > The commit itself shouldn't be the culprit. My guess is that the 8821CE > > > only leaves ASPM L1 for a short period when IRQ is raised. Since IRQ is > > > masked during NAPI polling, the PCIe link stays at L1 and makes RX DMA > > > extremely slow. Eventually the RX ring becomes messed up: > > > [ 1133.194697] rtw_8821ce 0000:02:00.0: pci bus timeout, check dma status > > > > > > Since the 8821CE hardware may fail to leave ASPM L1, manually do it in > > > the driver to resolve the issue. > > > > > > Fixes: 9e2fd29864c5 ("rtw88: add napi support") > > > Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215131 > > > BugLink: https://bugs.launchpad.net/bugs/1927808 > > > Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com> > > > --- > > > v2: > > > - Add default value for module parameter. > > > > > > drivers/net/wireless/realtek/rtw88/pci.c | 74 ++++++++---------------- > > > drivers/net/wireless/realtek/rtw88/pci.h | 1 + > > > 2 files changed, 24 insertions(+), 51 deletions(-) > > > > > > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c > > > index 3b367c9085eba..4ab75ac2500e9 100644 > > > --- a/drivers/net/wireless/realtek/rtw88/pci.c > > > +++ b/drivers/net/wireless/realtek/rtw88/pci.c > > > @@ -2,7 +2,6 @@ > > > /* Copyright(c) 2018-2019 Realtek Corporation > > > */ > > > > > > -#include <linux/dmi.h> > > > #include <linux/module.h> > > > #include <linux/pci.h> > > > #include "main.h" > > > @@ -16,10 +15,13 @@ > > > > > > static bool rtw_disable_msi; > > > static bool rtw_pci_disable_aspm; > > > +static int rtw_rx_aspm = -1; > > > module_param_named(disable_msi, rtw_disable_msi, bool, 0644); > > > module_param_named(disable_aspm, rtw_pci_disable_aspm, bool, 0644); > > > +module_param_named(rx_aspm, rtw_rx_aspm, int, 0444); > > > MODULE_PARM_DESC(disable_msi, "Set Y to disable MSI interrupt support"); > > > MODULE_PARM_DESC(disable_aspm, "Set Y to disable PCI ASPM support"); > > > +MODULE_PARM_DESC(rx_aspm, "Use PCIe ASPM for RX (0=disable, 1=enable, -1=default)"); > > > > > > static u32 rtw_pci_tx_queue_idx_addr[] = { > > > [RTW_TX_QUEUE_BK] = RTK_PCI_TXBD_IDX_BKQ, > > > @@ -1409,7 +1411,11 @@ static void rtw_pci_link_ps(struct rtw_dev *rtwdev, bool enter) > > > * throughput. This is probably because the ASPM behavior slightly > > > * varies from different SOC. > > > */ > > > - if (rtwpci->link_ctrl & PCI_EXP_LNKCTL_ASPM_L1) > > > + if (!(rtwpci->link_ctrl & PCI_EXP_LNKCTL_ASPM_L1)) > > > + return; > > > + > > > + if ((enter && atomic_dec_return(&rtwpci->link_usage) == 0) || > > > + (!enter && atomic_inc_return(&rtwpci->link_usage) == 1)) > > > rtw_pci_aspm_set(rtwdev, enter); > > > } > > > > > > > I found calling pci_link_ps isn't always symmetric, so we need to reset > > ref_cnt at pci_start() like below, or we can't enter rtw_pci_aspm_set() > > anymore. The negative flow I face is > > ifup -> connect AP -> ifdown -> ifup (ref_cnt isn't expected now). > > Is it expected to be asymmetric? > If it's intended to be this way, I'll change where we set link_usage. > Otherwise I think making it symmetric makes more sense. Agree with your thought, but I don't remember clearly why it enters idle twice in above flow. So, you may use two flags to indicate the state wanted by two callers. -- Ping-Ke
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