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iwlwifi: Add comments about MAC_ACCESS_REQ

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Signed-off-by: Ben Cahill <ben.m.cahill@intel.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Ben Cahill 2009-11-06 14:53:00 -08:00 committed by John W. Linville
parent 2a3b793d6a
commit a7e6611034
1 changed files with 20 additions and 0 deletions
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20
drivers/net/wireless/iwlwifi/iwl-io.h
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@ -200,6 +200,26 @@ static inline int _iwl_grab_nic_access(struct iwl_priv *priv)
/* this bit wakes up the NIC */
_iwl_set_bit(priv, CSR_GP_CNTRL, CSR_GP_CNTRL_REG_FLAG_MAC_ACCESS_REQ);
/*
* These bits say the device is running, and should keep running for
* at least a short while (at least as long as MAC_ACCESS_REQ stays 1),
* but they do not indicate that embedded SRAM is restored yet;
* 3945 and 4965 have volatile SRAM, and must save/restore contents
* to/from host DRAM when sleeping/waking for power-saving.
* Each direction takes approximately 1/4 millisecond; with this
* overhead, it's a good idea to grab and hold MAC_ACCESS_REQUEST if a
* series of register accesses are expected (e.g. reading Event Log),
* to keep device from sleeping.
*
* CSR_UCODE_DRV_GP1 register bit MAC_SLEEP == 0 indicates that
* SRAM is okay/restored. We don't check that here because this call
* is just for hardware register access; but GP1 MAC_SLEEP check is a
* good idea before accessing 3945/4965 SRAM (e.g. reading Event Log).
*
* 5000 series and later (including 1000 series) have non-volatile SRAM,
* and do not save/restore SRAM when power cycling.
*/
ret = _iwl_poll_bit(priv, CSR_GP_CNTRL,
CSR_GP_CNTRL_REG_VAL_MAC_ACCESS_EN,
(CSR_GP_CNTRL_REG_FLAG_MAC_CLOCK_READY |