On Fri, 2010-08-13 at 11:27 -0400, Luis R. Rodriguez wrote: 
quoted text
> From: Maxim Levitsky <maximlevitsky@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@atheros.com>
> Cc: Matthew Garrett <mjg59@srcf.ucam.org>
> Cc: Tim Gardner <tim.gardner@canonical.com>
> Cc: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
> Cc: stable@kernel.org
> Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
> Signed-off-by: Maxim Levitsky <maximlevitsky@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


quoted text
> 
>  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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