RE: [PATCH wireless-next v1 1/4] wifi: rtw88: sdio: Check the HISR RX_REQUEST bit in rtw_sdio_rx_isr()

[Ping-Ke Shih]

> -----Original Message-----
> From: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> Sent: Friday, May 19, 2023 12:18 AM
> To: linux-wireless@xxxxxxxxxxxxxxx
> Cc: linux-mmc@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; ulf.hansson@xxxxxxxxxx; kvalo@xxxxxxxxxx;
> tony0620emma@xxxxxxxxx; Peter Robinson <pbrobinson@xxxxxxxxx>; Ping-Ke Shih <pkshih@xxxxxxxxxxx>;
> jernej.skrabec@xxxxxxxxx; Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> Subject: [PATCH wireless-next v1 1/4] wifi: rtw88: sdio: Check the HISR RX_REQUEST bit in rtw_sdio_rx_isr()
> 
> rtw_sdio_rx_isr() is responsible for receiving data from the wifi chip
> and is called from the SDIO interrupt handler when the interrupt status
> register (HISR) has the RX_REQUEST bit set. After the first batch of
> data has been processed by the driver the wifi chip may have more data
> ready to be read, which is managed by a loop in rtw_sdio_rx_isr().
> 
> It turns out that there are cases where the RX buffer length (from the
> REG_SDIO_RX0_REQ_LEN register) does not match the data we receive. The
> following two cases were observed with a RTL8723DS card:
> - RX length is smaller than the total packet length including overhead
>   and actual data bytes (whose length is part of the buffer we read from
>   the wifi chip and is stored in rtw_rx_pkt_stat.pkt_len). This can
>   result in errors like:
>     skbuff: skb_over_panic: text:ffff8000011924ac len:3341 put:3341
>   (one case observed was: RX buffer length = 1536 bytes but
>    rtw_rx_pkt_stat.pkt_len = 1546 bytes, this is not valid as it means
>    we need to read beyond the end of the buffer)
> - RX length looks valid but rtw_rx_pkt_stat.pkt_len is zero
> 
> Check if the RX_REQUEST is set in the HISR register for each iteration
> inside rtw_sdio_rx_isr(). This mimics what the RTL8723DS vendor driver
> does and makes the driver only read more data if the RX_REQUEST bit is
> set (which seems to be a way for the card's hardware or firmware to
> tell the host that data is ready to be processed).
> 
> For RTW_WCPU_11AC chips this check is not needed. The RTL8822BS vendor
> driver for example states that this check is unnecessary (but still uses
> it) and the RTL8822CS drops this check entirely.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
> ---
>  drivers/net/wireless/realtek/rtw88/sdio.c | 23 ++++++++++++++++++++---
>  1 file changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw88/sdio.c b/drivers/net/wireless/realtek/rtw88/sdio.c
> index 06fce7c3adda..32b8c9194b2c 100644
> --- a/drivers/net/wireless/realtek/rtw88/sdio.c
> +++ b/drivers/net/wireless/realtek/rtw88/sdio.c
> @@ -998,9 +998,9 @@ static void rtw_sdio_rxfifo_recv(struct rtw_dev *rtwdev, u32 rx_len)
> 
>  static void rtw_sdio_rx_isr(struct rtw_dev *rtwdev)
>  {
> -       u32 rx_len, total_rx_bytes = 0;
> +       u32 rx_len, hisr, total_rx_bytes = 0;
> 
> -       while (total_rx_bytes < SZ_64K) {
> +       do {
>                 if (rtw_chip_wcpu_11n(rtwdev))
>                         rx_len = rtw_read16(rtwdev, REG_SDIO_RX0_REQ_LEN);
>                 else
> @@ -1012,7 +1012,24 @@ static void rtw_sdio_rx_isr(struct rtw_dev *rtwdev)
>                 rtw_sdio_rxfifo_recv(rtwdev, rx_len);
> 
>                 total_rx_bytes += rx_len;
> -       }
> +
> +               if (rtw_chip_wcpu_11n(rtwdev))
> +                       /* Stop if no more RX requests are pending, even if
> +                        * rx_len could be greater than zero in the next
> +                        * iteration. This is needed because the RX buffer may
> +                        * already contain data while either HW or FW are not
> +                        * done filling that buffer yet. Still reading the
> +                        * buffer can result in packets where
> +                        * rtw_rx_pkt_stat.pkt_len is zero or points beyond the
> +                        * end of the buffer.
> +                        */
> +                       hisr = rtw_read32(rtwdev, REG_SDIO_HISR);
> +               else
> +                       /* RTW_WCPU_11AC chips have improved hardware or
> +                        * firmware and can use rx_len unconditionally.
> +                        */
> +                       hisr = REG_SDIO_HISR_RX_REQUEST;

nit: adding braces to these branches would be clearer. 

If not, this patch still looks good to me, so

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


> +       } while (total_rx_bytes < SZ_64K && hisr & REG_SDIO_HISR_RX_REQUEST);
>  }
> 
>  static void rtw_sdio_handle_interrupt(struct sdio_func *sdio_func)
> --
> 2.40.1