> -----Original Message-----
> From: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> Sent: Tuesday, December 14, 2021 1:33 PM
> To: tony0620emma@xxxxxxxxx; Pkshih <pkshih@xxxxxxxxxxx>
> Cc: jian-hong@xxxxxxxxxxxx; Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>; Kalle Valo
> <kvalo@xxxxxxxxxxxxxx>; David S. Miller <davem@xxxxxxxxxxxxx>; Jakub Kicinski <kuba@xxxxxxxxxx>; Bernie
> Huang <phhuang@xxxxxxxxxxx>; Brian Norris <briannorris@xxxxxxxxxxxx>; linux-wireless@xxxxxxxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> 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@xxxxxxxxxxxxx>
> ---
> 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).
@@ -582,6 +582,8 @@ static int rtw_pci_start(struct rtw_dev *rtwdev)
rtw_pci_napi_start(rtwdev);
spin_lock_bh(&rtwpci->irq_lock);
+ atomic_set(&rtwpci->link_usage, 1);
rtwpci->running = true;
rtw_pci_enable_interrupt(rtwdev, rtwpci, false);
spin_unlock_bh(&rtwpci->irq_lock);
--
Ping-Ke
