From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 78EEB1950D for ; Wed, 24 May 2023 15:10:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DD444C433D2; Wed, 24 May 2023 15:10:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684941056; bh=1HziZk0Ofryk7MpDRZfUaSYzXybvtVckG6+PfRVCo1c=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=VtjnI42vjLtKXXQrmlFpD4S0MDxUXc3TpPumveYqzmCrv1phZPzw7aRVWX9r8I8yP YcjvDpK6GkfOBA/6OeuZwCDBgZ2WckqL/A+/9iwEtBPG9/SIwno60R6pfkl913ttyW nL25h06PJrbFVcD7bmLFRfSdcJJU5y29FLYXidHBuQRR+cf4ZNvdjD1T7PWAaVwSFC Rj0W0eGEa4LsxRsjwtWcKvGP92NeX3DdYfDctqQnAGbBjegMhH5WDiuy3f+XbD978d cu7RGX43IKJ6B0X2NNZRbNNbflLK2CP+uPHAUTIf75BZNgbEoakwdIXqFS2oTrmxBt 7JaVh7h5oEUrw== Date: Wed, 24 May 2023 10:10:54 -0500 From: Bjorn Helgaas To: Ilpo =?iso-8859-1?Q?J=E4rvinen?= Cc: linux-pci@vger.kernel.org, Bjorn Helgaas , Lorenzo Pieralisi , Rob Herring , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Emmanuel Grumbach , "Rafael J . Wysocki" , Heiner Kallweit , Lukas Wunner , Kalle Valo , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Michal Kazior , Janusz Dziedzic , ath10k@lists.infradead.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Dean Luick , Andy Shevchenko , stable@vger.kernel.org Subject: Re: [PATCH v2 9/9] wifi: ath10k: Use RMW accessors for changing LNKCTL Message-ID: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230517105235.29176-10-ilpo.jarvinen@linux.intel.com> On Wed, May 17, 2023 at 01:52:35PM +0300, Ilpo Järvinen wrote: > Don't assume that only the driver would be accessing LNKCTL. ASPM > policy changes can trigger write to LNKCTL outside of driver's control. > > Use RMW capability accessors which does proper locking to avoid losing > concurrent updates to the register value. On restore, clear the ASPMC > field properly. > > Fixes: 76d870ed09ab ("ath10k: enable ASPM") > Suggested-by: Lukas Wunner > Signed-off-by: Ilpo Järvinen > Cc: stable@vger.kernel.org > --- > drivers/net/wireless/ath/ath10k/pci.c | 9 +++++---- > 1 file changed, 5 insertions(+), 4 deletions(-) > > diff --git a/drivers/net/wireless/ath/ath10k/pci.c b/drivers/net/wireless/ath/ath10k/pci.c > index a7f44f6335fb..9275a672f90c 100644 > --- a/drivers/net/wireless/ath/ath10k/pci.c > +++ b/drivers/net/wireless/ath/ath10k/pci.c > @@ -1963,8 +1963,9 @@ static int ath10k_pci_hif_start(struct ath10k *ar) > ath10k_pci_irq_enable(ar); > ath10k_pci_rx_post(ar); > > - pcie_capability_write_word(ar_pci->pdev, PCI_EXP_LNKCTL, > - ar_pci->link_ctl); > + pcie_capability_clear_and_set_word(ar_pci->pdev, PCI_EXP_LNKCTL, > + PCI_EXP_LNKCTL_ASPMC, > + ar_pci->link_ctl & PCI_EXP_LNKCTL_ASPMC); > > return 0; > } > @@ -2821,8 +2822,8 @@ static int ath10k_pci_hif_power_up(struct ath10k *ar, > > pcie_capability_read_word(ar_pci->pdev, PCI_EXP_LNKCTL, > &ar_pci->link_ctl); > - pcie_capability_write_word(ar_pci->pdev, PCI_EXP_LNKCTL, > - ar_pci->link_ctl & ~PCI_EXP_LNKCTL_ASPMC); > + pcie_capability_clear_word(ar_pci->pdev, PCI_EXP_LNKCTL, > + PCI_EXP_LNKCTL_ASPMC); These ath drivers all have the form: 1) read LNKCTL 2) save LNKCTL value in ->link_ctl 3) write LNKCTL with "->link_ctl & ~PCI_EXP_LNKCTL_ASPMC" to disable ASPM 4) write LNKCTL with ->link_ctl, presumably to re-enable ASPM These patches close the hole between 1) and 3) where other LNKCTL updates could interfere, which is definitely a good thing. But the hole between 1) and 4) is much bigger and still there. Any update by the PCI core in that interval would be lost. Straw-man proposal: - Change pci_disable_link_state() so it ignores aspm_disabled and always disables ASPM even if platform firmware hasn't granted ownership. Maybe this should warn and taint the kernel. - Change drivers to use pci_disable_link_state() instead of writing LNKCTL directly. Bjorn