[PATCH v5] bus: mhi: host: don't free bhie tables during suspend/hibernation

[Jeff Hugo]

On 5/14/2025 2:14 AM, Muhammad Usama Anjum wrote:
> Fix dma_direct_alloc() failure at resume time during bhie_table
> allocation because of memory pressure. There is a report where at
> resume time, the memory from the dma doesn't get allocated and MHI
> fails to re-initialize.
> 
> To fix it, don't free the memory at power down during suspend /
> hibernation. Instead, use the same allocated memory again after every
> resume / hibernation. This patch has been tested with resume and
> hibernation both.
> 
> There are two allocations of bhie; rddm and fbc. Optimize both of those

There are 3, but you touch 2.  I just commented on this in v4.  Only 
touching two is fine (the device for the 3rd one doesn't need this), but 
the documentation must be accurate.

> allocations. The rddm is of constant size for a given hardware. While
> the fbc_image size depends on the firmware. If the firmware changes,
> we'll free and allocate new memory for it. This patch is moticated from

moticated?  Motivated maybe?

> the ath12k [1] and ath11k [2] patches. They don't free the memory and
> reuse the same memory if new size is same. The firmware caching hasn't
> been implemented for the drivers other than the nouveau. (The changing
> of firmware isn't tested/supported for wireless drivers. But let's
> follow the example patches here.)
> 
> [1] https://lore.kernel.org/all/20240419034034.2842-1-quic_bqiang@quicinc.com/
> [2] https://lore.kernel.org/all/20220506141448.10340-1-quic_akolli@quicinc.com/
> 
> Tested-on: WCN6855 WLAN.HSP.1.1-03926.13-QCAHSPSWPL_V2_SILICONZ_CE-2.52297.6
> Tested-on: WCN7850 hw2.0 WLAN.HMT.1.1.c5-00284-QCAHMTSWPL_V1.0_V2.0_SILICONZ-3
> 
> Acked-by: Jeff Johnson <jeff.johnson at oss.qualcomm.com>
> Tested-by: Baochen Qiang <quic_bqiang at quicinc.com>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum at collabora.com>
> ---
> Changes since v1:
> - Don't free bhie tables during suspend/hibernation only
> - Handle fbc_image changed size correctly
> - Remove fbc_image getting set to NULL in *free_bhie_table()
> 
> Changes since v2:
> - Remove the new mhi_partial_unprepare_after_power_down() and instead
>    update mhi_power_down_keep_dev() to use
>    mhi_power_down_unprepare_keep_dev() as suggested by Mani
> - Update all users of this API such as ath12k (previously only ath11k
>    was updated)
> - Define prev_fw_sz in docs
> - Do better alignment of comments
> 
> Changes since v3:
> - Fix state machine of ath12k by setting ATH12K_MHI_DEINIT with
>    ATH12K_MHI_POWER_OFF_KEEP_DEV state (Thanks Sebastian for testing and
>    finding the problem)
> - Use static with mhi_power_down_unprepare_keep_dev()
> - Remove crash log as it was showing that kworker wasn't able to
>    allocate memory.
> 
> Changes since v4:
> - Update desctiption

While I'm commenting on spelling, "description"


Code looks ok to me. I think we just need to hash out some of the 
documentation and this will be good to go.