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Message-ID: <87v7n72pg0.wl-tiwai@suse.de>
Date: Fri, 01 Aug 2025 14:31:43 +0200
From: Takashi Iwai <tiwai@...e.de>
To: "Luca Weiss" <luca.weiss@...rphone.com>
Cc: "Arnd Bergmann" <arnd@...nel.org>,
"Mark Brown" <broonie@...nel.org>,
"Wesley Cheng" <quic_wcheng@...cinc.com>,
"Arnd Bergmann" <arnd@...db.de>,
"Jaroslav Kysela" <perex@...ex.cz>,
"Takashi Iwai" <tiwai@...e.com>,
"Greg Kroah-Hartman"
<gregkh@...uxfoundation.org>,
"Dan Carpenter" <dan.carpenter@...aro.org>,
<linux-sound@...r.kernel.org>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] ALSA: qc_audio_offload: try to reduce address space confusion
On Fri, 01 Aug 2025 13:31:42 +0200,
Luca Weiss wrote:
>
> Hi Arnd,
>
> On Tue May 13, 2025 at 2:34 PM CEST, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@...db.de>
> >
> > uaudio_transfer_buffer_setup() allocates a buffer for the subs->dev
> > device, and the returned address for the buffer is a CPU local virtual
> > address that may or may not be in the linear mapping, as well as a DMA
> > address token that is accessible by the USB device, and this in turn
> > may or may not correspond to the physical address.
> >
> > The use in the driver however assumes that these addresses are the
> > linear map and the CPU physical address, respectively. Both are
> > nonportable here, but in the end only the virtual address gets
> > used by converting it to a physical address that gets mapped into
> > a second iommu.
> >
> > Make this more explicit by pulling the conversion out first
> > and warning if it is not part of the linear map, and using the
> > actual physical address to map into the iommu in place of the
> > dma address that may already be iommu-mapped into the usb host.
>
> This patch is breaking USB audio offloading on Qualcomm devices on 6.16,
> as tested on sm6350 and sc7280-based smartphones.
>
> [ 420.463176] q6afe-dai 3000000.remoteproc:glink-edge:apr:service@4:dais: AFE Port already open
> [ 420.472676] ------------[ cut here ]------------
> [ 420.472691] WARNING: CPU: 2 PID: 175 at sound/usb/qcom/qc_audio_offload.c:1056 handle_uaudio_stream_req+0xea8/0x13f8 [snd_usb_audio_qmi]
> [ 420.472726] Modules linked in: rfcomm zram zsmalloc zstd_compress algif_hash algif_skcipher bnep nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nf_tables nfnetlink ipv6 fuse uhid uinput snd_usb_audio_qmi q6asm_dai q6routing q6afe_dai q6usb q6afe_clocks q6adm q6asm snd_q6dsp_common q6afe q6core apr pdr_interface snd_soc_sm8250 snd_soc_qcom
> _common snd_soc_qcom_offload_utils snd_soc_qcom_sdw soundwire_bus soc_usb snd_soc_core snd_compress snd_usb_audio ath10k_snoc ath10k_core snd_hwdep snd_usbmidi_lib ath fastrpc snd_pcm mac80211 hci_uart qrtr_smd snd_timer btqca qcom_pd_mapper snd_rawmidi bluetooth libarc4 qcom_pdr_msg cfg80211 snd soundcore ecdh_generic ecc rfkill qrtr qcom_stats qcom_q6v5_pas ipa qcom_pil_info qcom_q6v5 qcom_common
> [ 420.473018] CPU: 2 UID: 0 PID: 175 Comm: kworker/u32:9 Tainted: G W 6.16.0 #1-postmarketos-qcom-sm6350 NONE
> [ 420.473033] Tainted: [W]=WARN
> [ 420.473038] Hardware name: Fairphone 4 (DT)
> [ 420.473045] Workqueue: qmi_msg_handler qmi_data_ready_work
> [ 420.473065] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [ 420.473075] pc : handle_uaudio_stream_req+0xea8/0x13f8 [snd_usb_audio_qmi]
> [ 420.473091] lr : handle_uaudio_stream_req+0xc84/0x13f8 [snd_usb_audio_qmi]
> [ 420.473104] sp : ffff800082f939a0
> [ 420.473110] x29: ffff800082f93b10 x28: ffff0000cfb796b8 x27: 0000000000008000
> [ 420.473128] x26: ffff0000842afc80 x25: ffffa8e75a23b0e0 x24: 0000000000008000
> [ 420.473145] x23: ffffa8e75a23bcf0 x22: ffff800082f93bd0 x21: 0000000000000000
> [ 420.473161] x20: ffff800082f93c98 x19: ffff0000939bb740 x18: ffffa8e77925a4d0
> [ 420.473178] x17: ffffffffffffffff x16: ffffa8e777ef9728 x15: ffffa8e77925a000
> [ 420.473194] x14: 0000000000000000 x13: 0000000000000dc0 x12: ffff800080000000
> [ 420.473211] x11: 0000000000000cc0 x10: 0000000000000001 x9 : ffffa8e77944b880
> [ 420.473227] x8 : ffffd719b5f4d000 x7 : ffff00009033da18 x6 : 0000000000000000
> [ 420.473244] x5 : 0000000000000000 x4 : ffff800082f93938 x3 : 0000000000000000
> [ 420.473260] x2 : 0000000000000000 x1 : ffff0000857790c0 x0 : 0000000000000000
> [ 420.473277] Call trace:
> [ 420.473283] handle_uaudio_stream_req+0xea8/0x13f8 [snd_usb_audio_qmi] (P)
> [ 420.473300] qmi_invoke_handler+0xbc/0x108
> [ 420.473314] qmi_handle_message+0x90/0x1a8
> [ 420.473326] qmi_data_ready_work+0x210/0x390
> [ 420.473339] process_one_work+0x150/0x3a0
> [ 420.473351] worker_thread+0x288/0x480
> [ 420.473362] kthread+0x118/0x1e0
> [ 420.473375] ret_from_fork+0x10/0x20
> [ 420.473390] ---[ end trace 0000000000000000 ]---
> [ 420.479244] qcom-q6afe aprsvc:service:4:4: cmd = 0x100e5 returned error = 0x1
> [ 420.479540] qcom-q6afe aprsvc:service:4:4: DSP returned error[1]
> [ 420.479558] qcom-q6afe aprsvc:service:4:4: AFE enable for port 0x7000 failed -22
> [ 420.479572] q6afe-dai 3000000.remoteproc:glink-edge:apr:service@4:dais: fail to start AFE port 88
> [ 420.479583] q6afe-dai 3000000.remoteproc:glink-edge:apr:service@4:dais: ASoC error (-22): at snd_soc_dai_prepare() on USB_RX
>
> Reverting this patch makes it work as expected on 6.16.0.
>
> Let me know if I can be of any help to resolve this.
I guess just dropping WARN_ON() would help?
As far as I read the code, pa argument isn't used at all in
uaudio_iommu_map() unless as sgt is NULL. In this case, sgt is never
NULL, hence the pa argument is just a placeholder.
That said, the whole xfer_buf_pa (and its sanity check) can be dropped
there.
Takashi
--- a/sound/usb/qcom/qc_audio_offload.c
+++ b/sound/usb/qcom/qc_audio_offload.c
@@ -1020,7 +1020,6 @@ static int uaudio_transfer_buffer_setup(struct snd_usb_substream *subs,
struct sg_table xfer_buf_sgt;
dma_addr_t xfer_buf_dma;
void *xfer_buf;
- phys_addr_t xfer_buf_pa;
u32 len = xfer_buf_len;
bool dma_coherent;
dma_addr_t xfer_buf_dma_sysdev;
@@ -1051,18 +1050,13 @@ static int uaudio_transfer_buffer_setup(struct snd_usb_substream *subs,
if (!xfer_buf)
return -ENOMEM;
- /* Remapping is not possible if xfer_buf is outside of linear map */
- xfer_buf_pa = virt_to_phys(xfer_buf);
- if (WARN_ON(!page_is_ram(PFN_DOWN(xfer_buf_pa)))) {
- ret = -ENXIO;
- goto unmap_sync;
- }
dma_get_sgtable(subs->dev->bus->sysdev, &xfer_buf_sgt, xfer_buf,
xfer_buf_dma, len);
/* map the physical buffer into sysdev as well */
+ /* note: NULL passed to pa argument as we use sgt */
xfer_buf_dma_sysdev = uaudio_iommu_map(MEM_XFER_BUF, dma_coherent,
- xfer_buf_pa, len, &xfer_buf_sgt);
+ NULL, len, &xfer_buf_sgt);
if (!xfer_buf_dma_sysdev) {
ret = -ENOMEM;
goto unmap_sync;
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