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From: Maxim Levitsky on 13 Aug 2010 11:50
On Fri, 2010-08-13 at 11:27 -0400, Luis R. Rodriguez wrote:
> From: Maxim Levitsky <maximlevitsky(a)gmail.com>
>
> Atheros PCIe wireless cards handled by ath5k do require L0s disabled.
> For distributions shipping with CONFIG_PCIEASPM (this will be enabled
> by default in the future in 2.6.36) this will also mean both L1 and L0s
> will be disabled when a pre 1.1 PCIe device is detected. We do know L1
> works correctly even for all ath5k pre 1.1 PCIe devices though but cannot
> currently undue the effect of a blacklist, for details you can read
> pcie_aspm_sanity_check() and see how it adjusts the device link
> capability.
>
> It may be possible in the future to implement some PCI API to allow
> drivers to override blacklists for pre 1.1 PCIe but for now it is
> best to accept that both L0s and L1 will be disabled completely for
> distributions shipping with CONFIG_PCIEASPM rather than having this
> issue present. Motivation for adding this new API will be to help
> with power consumption for some of these devices.
>
> Example of issues you'd see:
>
> - On the Acer Aspire One (AOA150, Atheros Communications Inc. AR5001
> Wireless Network Adapter [168c:001c] (rev 01)) doesn't work well
> with ASPM enabled, the card will eventually stall on heavy traffic
> with often 'unsupported jumbo' warnings appearing. Disabling
> ASPM L0s in ath5k fixes these problems.
>
> - On the same card you would see a storm of RXORN interrupts
> even though medium is idle.
>
> Credit for root causing and fixing the bug goes to Jussi Kivilinna.
>
> Cc: David Quan <David.Quan(a)atheros.com>
> Cc: Matthew Garrett <mjg59(a)srcf.ucam.org>
> Cc: Tim Gardner <tim.gardner(a)canonical.com>
> Cc: Jussi Kivilinna <jussi.kivilinna(a)mbnet.fi>
> Cc: stable(a)kernel.org
> Signed-off-by: Luis R. Rodriguez <lrodriguez(a)atheros.com>
> Signed-off-by: Maxim Levitsky <maximlevitsky(a)gmail.com>
> ---
>
> Maxim, it was just reported this patch never made it upstream
> so I just took the liberty to submit it and also clear up the
> commit log and comments a little more in terms of actual impact
> and possible future fixes. I've also Cc'd stable so this can
> get propagated down to 2.6.32 as well.
Sure. In fact I don't deserve much credit on this patch. It is just one
line and besides ASPM is disabled anyway.

Thanks for Jussi Kivilinna again for finding this.

Best regards,
Maxim Levitsky


>
> drivers/net/wireless/ath/ath5k/base.c | 21 +++++++++++++++++++++
> 1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath5k/base.c b/drivers/net/wireless/ath/ath5k/base.c
> index 0d5de25..373dcfe 100644
> --- a/drivers/net/wireless/ath/ath5k/base.c
> +++ b/drivers/net/wireless/ath/ath5k/base.c
> @@ -48,6 +48,7 @@
> #include <linux/netdevice.h>
> #include <linux/cache.h>
> #include <linux/pci.h>
> +#include <linux/pci-aspm.h>
> #include <linux/ethtool.h>
> #include <linux/uaccess.h>
> #include <linux/slab.h>
> @@ -476,6 +477,26 @@ ath5k_pci_probe(struct pci_dev *pdev,
> int ret;
> u8 csz;
>
> + /*
> + * L0s needs to be disabled on all ath5k cards.
> + *
> + * For distributions shipping with CONFIG_PCIEASPM (this will be enabled
> + * by default in the future in 2.6.36) this will also mean both L1 and
> + * L0s will be disabled when a pre 1.1 PCIe device is detected. We do
> + * know L1 works correctly even for all ath5k pre 1.1 PCIe devices
> + * though but cannot currently undue the effect of a blacklist, for
> + * details you can read pcie_aspm_sanity_check() and see how it adjusts
> + * the device link capability.
> + *
> + * It may be possible in the future to implement some PCI API to allow
> + * drivers to override blacklists for pre 1.1 PCIe but for now it is
> + * best to accept that both L0s and L1 will be disabled completely for
> + * distributions shipping with CONFIG_PCIEASPM rather than having this
> + * issue present. Motivation for adding this new API will be to help
> + * with power consumption for some of these devices.
> + */
> + pci_disable_link_state(pdev, PCIE_LINK_STATE_L0S);
> +
> ret = pci_enable_device(pdev);
> if (ret) {
> dev_err(&pdev->dev, "can't enable device\n");


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