Re: [PATCH v5 5/6] wifi: ath11k: Add support for MHI bandwidth scaling

[Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>]

On 9/1/2026 8:15 PM, Neil Armstrong wrote:
> Hi,
>
> On 8/19/26 15:25, Krishna Chaitanya Chundru wrote:
>> From: Miaoqing Pan <quic_miaoqing@quicinc.com>
>>
>> Add support for MHI bandwidth scaling, which will reduce power consumption
>> if WLAN operates with lower bandwidth. This feature is only enabled for
>> QCA6390.
>>
>> Bandwidth scaling is initiated by the endpoint firmware based upon the
>> bandwidth requirements, if there is high bandwidth data endpoint requests
>> for higher data rates or if there is less bandwidth they request for lower
>> data rates to reduce power. Endpoint initiates this through MHI protocol.
>>
>> Tested-on: WCN6855 hw2.1 PCI
>> WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1
>
> Somehow unrelated, but I added this to the ath12k to test on an WCN785x and
> I just
> got a single event to set the speed to 5GT/s and no further event whatever
> the state
> of the Wireless link is.
>
> Is there anything required on the ath12k side to allow lowering the speed to
> 2.5GT/s ? 
some wifi device has some limitation due to that they will stay in gen2 only.

- Krishna Chaitanya.
>
> Thanks,
> Neil
>
>>
>> Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>
>> Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@oss.qualcomm.com>
>> ---
>>   drivers/net/wireless/ath/ath11k/mhi.c | 38
>> +++++++++++++++++++++++++++++++++++
>>   1 file changed, 38 insertions(+)
>>
>> diff --git a/drivers/net/wireless/ath/ath11k/mhi.c
>> b/drivers/net/wireless/ath/ath11k/mhi.c
>> index a6c9ff112c68..9bff4c4bca3b 100644
>> --- a/drivers/net/wireless/ath/ath11k/mhi.c
>> +++ b/drivers/net/wireless/ath/ath11k/mhi.c
>> @@ -20,6 +20,7 @@
>>   #define MHI_TIMEOUT_DEFAULT_MS    20000
>>   #define RDDM_DUMP_SIZE    0x420000
>>   #define MHI_CB_INVALID    0xff
>> +#define MHI_BW_SCALE_CHAN_DB 126
>>     static const struct mhi_channel_config ath11k_mhi_channels_qca6390[] = {
>>       {
>> @@ -71,6 +72,17 @@ static struct mhi_event_config
>> ath11k_mhi_events_qca6390[] = {
>>           .client_managed = false,
>>           .offload_channel = false,
>>       },
>> +    {
>> +        .num_elements = 8,
>> +        .irq_moderation_ms = 0,
>> +        .irq = 1,
>> +        .mode = MHI_DB_BRST_DISABLE,
>> +        .data_type = MHI_ER_BW_SCALE,
>> +        .priority = 2,
>> +        .hardware_event = false,
>> +        .client_managed = false,
>> +        .offload_channel = false,
>> +    },
>>   };
>>     static const struct mhi_controller_config ath11k_mhi_config_qca6390 = {
>> @@ -311,6 +323,30 @@ static void ath11k_mhi_op_write_reg(struct
>> mhi_controller *mhi_cntrl,
>>       writel(val, addr);
>>   }
>>   +static int ath11k_mhi_op_get_misc_doorbell(struct mhi_controller
>> *mhi_cntrl,
>> +                       enum mhi_er_data_type type)
>> +{
>> +    if (type == MHI_ER_BW_SCALE)
>> +        return MHI_BW_SCALE_CHAN_DB;
>> +
>> +    return -EOPNOTSUPP;
>> +}
>> +
>> +static int ath11k_mhi_op_bw_scale(struct mhi_controller *mhi_cntrl,
>> +                  struct mhi_link_info *link_info)
>> +{
>> +    enum pci_bus_speed speed =
>> pci_lnkctl2_bus_speed(link_info->target_link_speed);
>> +    struct ath11k_base *ab = dev_get_drvdata(mhi_cntrl->cntrl_dev);
>> +    struct pci_dev *pci_dev = to_pci_dev(ab->dev);
>> +    struct pci_dev *pdev;
>> +
>> +    pdev = pci_upstream_bridge(pci_dev);
>> +    if (!pdev)
>> +        return -ENODEV;
>> +
>> +    return pcie_set_target_speed(pdev, speed, true);
>> +}
>> +
>>   static int ath11k_mhi_read_addr_from_dt(struct mhi_controller *mhi_ctrl)
>>   {
>>       struct device_node *np;
>> @@ -387,6 +423,8 @@ int ath11k_mhi_register(struct ath11k_pci *ab_pci)
>>       mhi_ctrl->status_cb = ath11k_mhi_op_status_cb;
>>       mhi_ctrl->read_reg = ath11k_mhi_op_read_reg;
>>       mhi_ctrl->write_reg = ath11k_mhi_op_write_reg;
>> +    mhi_ctrl->bw_scale = ath11k_mhi_op_bw_scale;
>> +    mhi_ctrl->get_misc_doorbell = ath11k_mhi_op_get_misc_doorbell;
>>         switch (ab->hw_rev) {
>>       case ATH11K_HW_QCN9074_HW10:
>>
>