From: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx> commit 2d93aee152b1758a94a18fe15d72153ba73b5679 upstream. Enabling the oscillator consumes slightly more power (100uA) but allows to make sure that we exit from L1 on time. Not doing so might lead to a PCIe specification violation since we might wake up from L1 at the wrong time. This issue has been identified on 3160 and 7260 only. On older NICs L1 off is not enabled, on newer NICs (7265), the issue is fixed. When the bug occurs the user sees that the NIC has disappeared from the PCI bridge, any access to the device returns 0xff. This fixes: https://bugzilla.kernel.org/show_bug.cgi?id=64541 and has been extensively discussed here: http://markmail.org/thread/mfmpzqt3r333n4bo Cc: stable@xxxxxxxxxxxxxxx [3.10+] Fixes: 99cd47142399 ("iwlwifi: add 7000 series device configuration") Reported-and-tested-by: wzyboy <wzyboy@xxxxxxxxxx> Reviewed-by: Johannes Berg <johannes.berg@xxxxxxxxx> Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@xxxxxxxxx> --- I modified the upstream commit to compile on 3.10. I simply had to remove the if. The if asks if we are not dealing with a new device that doesn't need this HW W/A, but this newer HW isn't supported at all in 3.10. So no condition needed. --- drivers/net/wireless/iwlwifi/iwl-prph.h | 4 ++++ drivers/net/wireless/iwlwifi/pcie/trans.c | 16 ++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/drivers/net/wireless/iwlwifi/iwl-prph.h b/drivers/net/wireless/iwlwifi/iwl-prph.h index 386f2a7..c26a6dc 100644 --- a/drivers/net/wireless/iwlwifi/iwl-prph.h +++ b/drivers/net/wireless/iwlwifi/iwl-prph.h @@ -260,4 +260,8 @@ static inline unsigned int SCD_QUEUE_STATUS_BITS(unsigned int chnl) /*********************** END TX SCHEDULER *************************************/ +/* Oscillator clock */ +#define OSC_CLK (0xa04068) +#define OSC_CLK_FORCE_CONTROL (0x8) + #endif /* __iwl_prph_h__ */ diff --git a/drivers/net/wireless/iwlwifi/pcie/trans.c b/drivers/net/wireless/iwlwifi/pcie/trans.c index aeb70e1..95ed2a6 100644 --- a/drivers/net/wireless/iwlwifi/pcie/trans.c +++ b/drivers/net/wireless/iwlwifi/pcie/trans.c @@ -207,6 +207,22 @@ static int iwl_pcie_apm_init(struct iwl_trans *trans) } /* + * Enable the oscillator to count wake up time for L1 exit. This + * consumes slightly more power (100uA) - but allows to be sure + * that we wake up from L1 on time. + * + * This looks weird: read twice the same register, discard the + * value, set a bit, and yet again, read that same register + * just to discard the value. But that's the way the hardware + * seems to like it. + */ + iwl_read_prph(trans, OSC_CLK); + iwl_read_prph(trans, OSC_CLK); + iwl_set_bits_prph(trans, OSC_CLK, OSC_CLK_FORCE_CONTROL); + iwl_read_prph(trans, OSC_CLK); + iwl_read_prph(trans, OSC_CLK); + + /* * Enable DMA clock and wait for it to stabilize. * * Write to "CLK_EN_REG"; "1" bits enable clocks, while "0" bits -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html