RE: [PATCH v3 1/2] wifi: rtw88: sdio: Fix unhandled RX request interrupt storm

[Ping-Ke Shih]

Alastair D'Silva <alastair@xxxxxxxxxxx> wrote:
> 8051 and 3081 SDIO chipsets handle the REG_SDIO_HISR_RX_REQUEST status bit
> differently:
> 
> - 8051-based chips (e.g. RTL8723BS, RTL8723CS, RTL8723DS):
>   The hardware automatically clears REG_SDIO_HISR_RX_REQUEST once the RX
>   buffer is empty. Software must not clear this bit, because the drain
>   loop in rtw_sdio_rx_isr() re-reads REG_SDIO_HISR across iterations to
>   decide whether more requests are pending. Clearing it in software
>   terminates the loop after a single request, stranding the remainder of
>   the FIFO. Additionally, RTL8723BS requires RTW_SDIO_HISR_CLEAR_MASK to
>   avoid undefined bits causing resume storms.
> 
> - 3081-based chips (e.g. RTL8821CS, RTL8822CS):
>   The hardware does not automatically clear REG_SDIO_HISR_RX_REQUEST when
>   the RX buffer is empty. Masking this bit out in software before writing
>   back to HISR prevented it from ever being acknowledged in hardware,
>   trapping the CPU core in an infinite interrupt storm loop that starved
>   RCU and locked up the system. Furthermore, on 3081 chips the physical
>   RX FIFO capacity is at most 24 KB (16 KB on RTL8821CS, 24 KB on
>   RTL8822CS), which is well within the 64 KB loop budget.
> 
> As the number of architecture-specific special cases has grown (16-bit vs
> 32-bit register widths, differing HISR writeback timing, synthetic loop
> flags, and RTL8723BS resume masking), attempting to accommodate both
> architectures within a single monolithic handler has become fragile and
> prone to cross-architecture regressions.
> 
> Resolve this by making rtw_sdio_handle_interrupt() a dispatcher with
> separate paths for 8051 and 3081:
> 
> 1. 8051 chips preserve the existing unmasked writeback behavior, leaving
>    REG_SDIO_HISR_RX_REQUEST for hardware to drop and respecting
>    RTW_SDIO_HISR_CLEAR_MASK on RTL8723BS.
> 2. 3081 chips adopt the interrupt masking pattern: disable HIMR,
>    acknowledge pending status bits in HISR via W1C, service the pending
>    events, and re-enable HIMR. Any packet arriving during servicing
>    latches REG_SDIO_HISR_RX_REQUEST in hardware and re-asserts the IRQ line
>    once unmasked.
> 
> Splitting into separate handlers isolates these quirks cleanly and
> simplifies future maintenance.
> 
> Fixes: 65371a3f14e7 ("wifi: rtw88: sdio: Add HCI implementation for SDIO based chipsets")

At this moment, did it support 3081-seris already?
I feel this tag is too serious. 

> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>

Acked-by: Ping-Ke Shih <pkshih@xxxxxxxxxxx>