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From:   Arend van Spriel <aspriel@gmail.com>
To:     Fabio Estevam <festevam@denx.de>, <kvalo@codeaurora.org>
CC:     <ath10k@lists.infradead.org>, <linux-wireless@vger.kernel.org>,
        <hch@lst.de>, <erik.stromdahl@gmail.com>
Date:   Wed, 18 Aug 2021 18:48:15 +0200
Message-ID: <17b5a29d098.279b.9696ff82abe5fb6502268bdc3b0467d4@gmail.com>
In-Reply-To: <20210818150943.1630199-1-festevam@denx.de>
References: <20210818150943.1630199-1-festevam@denx.de>
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Subject: Re: [PATCH] ath10k: Do not call dma_alloc_coherent() for SDIO and USB
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On August 18, 2021 5:11:10 PM Fabio Estevam <festevam@denx.de> wrote:

> When running the "hostapd" application on a i.MX7-based board with
> an ath10k device connected via SDIO, the following warning is seen:
>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 489 at kernel/dma/mapping.c:427 dma_alloc_attrs+0xd0/0x114
> Modules linked in: ath10k_sdio ath10k_core ath
> CPU: 0 PID: 489 Comm: hostapd Not tainted 5.10.48-stable-standard #1
> Hardware name: Freescale i.MX7 Dual (Device Tree)
> [<c0111378>] (unwind_backtrace) from [<c010bc04>] (show_stack+0x10/0x14)
> [<c010bc04>] (show_stack) from [<c0e26094>] (dump_stack+0xdc/0x104)
> [<c0e26094>] (dump_stack) from [<c0125574>] (__warn+0xd8/0x114)
> [<c0125574>] (__warn) from [<c0e20ecc>] (warn_slowpath_fmt+0x60/0xbc)
> [<c0e20ecc>] (warn_slowpath_fmt) from [<c01b9eac>] (dma_alloc_attrs+0xd0/0x114)
> [<c01b9eac>] (dma_alloc_attrs) from [<bf01373c>] 
> (ath10k_add_interface+0x2f0/0x1094 [ath10k_core])
> [<bf01373c>] (ath10k_add_interface [ath10k_core]) from [<c0d94470>] 
> (drv_add_interface+0x88/0x2fc)
>
> As explained by Christoph Hellwig:
>
> "Looking at the ath10k code ar->dev is set by ath10k_core_create, which
> has multiple callers.
>
> For ath10k_pci_probe it is a pci_dev, which should always have a
> dma_mask.
>
> For ath10k_ahb_probe is a device tree probed platform_device,
> which should have a dma mask.
>
> For ath10k_sdio_probe it is a sdio_func, which from my understanding is
> a virtual device can't do DMA itself.
>
> For ath10k_snoc_probe it is a platform device with an explicit
> dma_set_mask_and_coherent and above so the dma_mask is set.
>
> For ath10k_usb_probe it is an usb device which can't do USB."
>
> Fix the problem by not calling dma_alloc_coherent() when the device
> is not DMA capable, such as SDIO and USB.
>
> Signed-off-by: Fabio Estevam <festevam@denx.de>
> ---
> Hi,
>
> I am not certain about the proper commit to include in the Fixes tag.
>
> Any suggestions?
>
> Thanks
>
> drivers/net/wireless/ath/ath10k/mac.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath10k/mac.c 
> b/drivers/net/wireless/ath/ath10k/mac.c
> index c272b290fa73..e85c3f107d2e 100644
> --- a/drivers/net/wireless/ath/ath10k/mac.c
> +++ b/drivers/net/wireless/ath/ath10k/mac.c
> @@ -5576,15 +5576,17 @@ static int ath10k_add_interface(struct ieee80211_hw 
> *hw,
>  if (vif->type == NL80211_IFTYPE_ADHOC ||
>     vif->type == NL80211_IFTYPE_MESH_POINT ||
>     vif->type == NL80211_IFTYPE_AP) {
> - arvif->beacon_buf = dma_alloc_coherent(ar->dev,
> -       IEEE80211_MAX_FRAME_LEN,
> -       &arvif->beacon_paddr,
> -       GFP_ATOMIC);
> - if (!arvif->beacon_buf) {
> - ret = -ENOMEM;
> - ath10k_warn(ar, "failed to allocate beacon buffer: %d\n",
> -    ret);
> - goto err;
> + if (!(ar->hif.bus == ATH10K_BUS_SDIO) && !(ar->hif.bus == ATH10K_BUS_USB)) {

Does this mean you can not really setup a beaconing interface type for SDIO 
and USB?

Regards,
Arend