On Mon, 20 Nov 2023 at 12:57, Martin Blumenstingl
<[email protected]> wrote:
>
> Lukas reports skb_over_panic errors on his Banana Pi BPI-CM4 which comes
> with an Amlogic A311D (G12B) SoC and a RTL8822CS SDIO wifi/Bluetooth
> combo card. The error he observed is identical to what has been fixed
> in commit e967229ead0e ("wifi: rtw88: sdio: Check the HISR RX_REQUEST
> bit in rtw_sdio_rx_isr()") but that commit didn't fix Lukas' problem.
>
> Lukas found that disabling or limiting RX aggregation works around the
> problem for some time (but does not fully fix it). In the following
> discussion a few key topics have been discussed which have an impact on
> this problem:
> - The Amlogic A311D (G12B) SoC has a hardware bug in the SDIO controller
> which prevents DMA transfers. Instead all transfers need to go through
> the controller SRAM which limits transfers to 1536 bytes
> - rtw88 chips don't split incoming (RX) packets, so if a big packet is
> received this is forwarded to the host in it's original form
> - rtw88 chips can do RX aggregation, meaning more multiple incoming
> packets can be pulled by the host from the card with one MMC/SDIO
> transfer. This Depends on settings in the REG_RXDMA_AGG_PG_TH
> register (BIT_RXDMA_AGG_PG_TH limits the number of packets that will
> be aggregated, BIT_DMA_AGG_TO_V1 configures a timeout for aggregation
> and BIT_EN_PRE_CALC makes the chip honor the limits more effectively)
>
> Use multiple consecutive reads in rtw_sdio_read_port() and limit the
> number of bytes which are copied by the host from the card in one
> MMC/SDIO transfer. This allows receiving a buffer that's larger than
> the hosts max_req_size (number of bytes which can be transferred in
> one MMC/SDIO transfer). As a result of this the skb_over_panic error
> is gone as the rtw88 driver is now able to receive more than 1536 bytes
> from the card (either because the incoming packet is larger than that
> or because multiple packets have been aggregated).
>
> In case of an receive errors (-EILSEQ has been observed by Lukas) we
> need to drain the remaining data from the card's buffer, otherwise the
> card will return corrupt data for the next rtw_sdio_read_port() call.
>
> Fixes: 65371a3f14e7 ("wifi: rtw88: sdio: Add HCI implementation for SDIO based chipsets")
> Reported-by: Lukas F. Hartmann <[email protected]>
> Closes: https://lore.kernel.org/linux-wireless/CAFBinCBaXtebixKbjkWKW_WXc5k=NdGNaGUjVE8NCPNxOhsb2g@mail.gmail.com/
> Suggested-by: Ping-Ke Shih <[email protected]>
> Signed-off-by: Martin Blumenstingl <[email protected]>
From the SDIO interface point of view, feel free to add:
Reviewed-by: Ulf Hansson <[email protected]>
Kind regards
Uffe
> ---
>
> Changes since v2 at [2]:
> - Don't initialize err to zero as that intiial value is never used.
> Thanks Ping-Ke for spotting this!
> - Add a comment explaning why we need to continue reading but still
> have to return an error to the caller of rtw_sdio_read_port()
>
> Changes since v1 at [0]:
> - We need to read all bytes if we split the transaction into multiple
> smaller reads. This is even the case when one of N reads reports an
> error. Otherwise the next read port call will return garbage (partially
> containing zeros, ...). A similar-ish approach can be found in the
> vendor driver, see [1] (specifically the call to sdio_recv_and_drop())
> - Update the patch description accordingly
>
> With a preliminary version of this updated patch Lukas reported off-
> list: "i've been using this laptop for almost 3 hours with heavy wifi
> usage and so far no problems"
>
>
> [0] https://lore.kernel.org/lkml/[email protected]/T/
> [1] https://github.com/chewitt/RTL8822CS/blob/ad1391e219b59314485739a499fb442d5bbc069e/hal/rtl8822c/sdio/rtl8822cs_io.c#L468-L477
> [2] https://lore.kernel.org/linux-wireless/[email protected]/
>
>
> drivers/net/wireless/realtek/rtw88/sdio.c | 35 ++++++++++++++++++-----
> 1 file changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/net/wireless/realtek/rtw88/sdio.c b/drivers/net/wireless/realtek/rtw88/sdio.c
> index 2c1fb2dabd40..0cae5746f540 100644
> --- a/drivers/net/wireless/realtek/rtw88/sdio.c
> +++ b/drivers/net/wireless/realtek/rtw88/sdio.c
> @@ -500,19 +500,40 @@ static u32 rtw_sdio_get_tx_addr(struct rtw_dev *rtwdev, size_t size,
> static int rtw_sdio_read_port(struct rtw_dev *rtwdev, u8 *buf, size_t count)
> {
> struct rtw_sdio *rtwsdio = (struct rtw_sdio *)rtwdev->priv;
> + struct mmc_host *host = rtwsdio->sdio_func->card->host;
> bool bus_claim = rtw_sdio_bus_claim_needed(rtwsdio);
> u32 rxaddr = rtwsdio->rx_addr++;
> - int ret;
> + int ret = 0, err;
> + size_t bytes;
>
> if (bus_claim)
> sdio_claim_host(rtwsdio->sdio_func);
>
> - ret = sdio_memcpy_fromio(rtwsdio->sdio_func, buf,
> - RTW_SDIO_ADDR_RX_RX0FF_GEN(rxaddr), count);
> - if (ret)
> - rtw_warn(rtwdev,
> - "Failed to read %zu byte(s) from SDIO port 0x%08x",
> - count, rxaddr);
> + while (count > 0) {
> + bytes = min_t(size_t, host->max_req_size, count);
> +
> + err = sdio_memcpy_fromio(rtwsdio->sdio_func, buf,
> + RTW_SDIO_ADDR_RX_RX0FF_GEN(rxaddr),
> + bytes);
> + if (err) {
> + rtw_warn(rtwdev,
> + "Failed to read %zu byte(s) from SDIO port 0x%08x: %d",
> + bytes, rxaddr, err);
> +
> + /* Signal to the caller that reading did not work and
> + * that the data in the buffer is short/corrupted.
> + */
> + ret = err;
> +
> + /* Don't stop here - instead drain the remaining data
> + * from the card's buffer, else the card will return
> + * corrupt data for the next rtw_sdio_read_port() call.
> + */
> + }
> +
> + count -= bytes;
> + buf += bytes;
> + }
>
> if (bus_claim)
> sdio_release_host(rtwsdio->sdio_func);
> --
> 2.42.1
>