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    Subject[PATCH AUTOSEL for 4.9 174/219] iwlwifi: mvm: rs: don't override the rate history in the search cycle
    Date
    From: Emmanuel Grumbach <emmanuel.grumbach@intel.com>

    [ Upstream commit 992172e3aec19e5b0ea5b757ba40a146b9282d1e ]

    When we are in a search cycle, we try different combinations
    of parameters. Those combinations are called 'columns'.
    When we switch to a new column, we first need to check if
    this column has a suitable rate, if not, we can't try it.
    This means we must not erase the statistics we gathered
    for the previous column until we are sure that we are
    indeed switching column.

    The code that tries to switch to a new column first sets
    a whole bunch of things for the new column, and only then
    checks that we can find suitable rates in that column.
    While doing that, the code mistakenly erased the rate
    statistics. This code was right until
    struct iwl_scale_tbl_info grew up for TPC.

    Fix this to make sure we don't erase the rate statistics
    until we are sure that we can indeed switch to the new
    column.

    Note that this bug is really harmless since it causes a
    change in the behavior only when we can't find any rate
    in the new column which should really not happen. In the
    case we do find a suitable we reset the rate statistics
    a few lines later anyway.

    Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
    Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
    Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    ---
    drivers/net/wireless/intel/iwlwifi/mvm/rs.c | 4 +---
    1 file changed, 1 insertion(+), 3 deletions(-)

    diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
    index 227c5ed9cbe6..0aea476ebf50 100644
    --- a/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
    +++ b/drivers/net/wireless/intel/iwlwifi/mvm/rs.c
    @@ -1867,12 +1867,10 @@ static int rs_switch_to_column(struct iwl_mvm *mvm,
    struct rs_rate *rate = &search_tbl->rate;
    const struct rs_tx_column *column = &rs_tx_columns[col_id];
    const struct rs_tx_column *curr_column = &rs_tx_columns[tbl->column];
    - u32 sz = (sizeof(struct iwl_scale_tbl_info) -
    - (sizeof(struct iwl_rate_scale_data) * IWL_RATE_COUNT));
    unsigned long rate_mask = 0;
    u32 rate_idx = 0;

    - memcpy(search_tbl, tbl, sz);
    + memcpy(search_tbl, tbl, offsetof(struct iwl_scale_tbl_info, win));

    rate->sgi = column->sgi;
    rate->ant = column->ant;
    --
    2.14.1
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