On Tue, 10 Sep 2019 09:52:13 +0200, Arnd Bergmann wrote: > > On Tue, Sep 10, 2019 at 9:06 AM Takashi Iwai <tiwai@xxxxxxx> wrote: > > On Mon, 09 Sep 2019 22:51:23 +0200, Arnd Bergmann wrote: > > > > > > On Mon, Sep 9, 2019 at 10:39 PM Pierre-Louis Bossart > > > <pierre-louis.bossart@xxxxxxxxxxxxxxx> wrote: > > > > > > > > On 9/9/19 2:51 PM, Arnd Bergmann wrote: > > > > > When CONFIG_SND_HDA_ALIGNED_MMIO is selected by another driver > > > > > (i.e. Tegra) that selects CONFIG_SND_HDA_CORE as a loadable > > > > > module, but SND_SOC_SOF_HDA_COMMON is built-in, we get a > > > > > link failure from some functions that access the hda register: > > > > > > > > > > sound/soc/sof/intel/hda.o: In function `hda_ipc_irq_dump': > > > > > hda.c:(.text+0x784): undefined reference to `snd_hdac_aligned_read' > > > > > sound/soc/sof/intel/hda-stream.o: In function `hda_dsp_stream_threaded_handler': > > > > > hda-stream.c:(.text+0x12e4): undefined reference to `snd_hdac_aligned_read' > > > > > hda-stream.c:(.text+0x12f8): undefined reference to `snd_hdac_aligned_write' > > > > > > > > > > Add an explicit 'select' statement as a workaround. This is > > > > > not a great solution, but it's the easiest way I could come > > > > > up with. > > > > > > > > Thanks for spotting this, I don't think anyone on the SOF team looked at > > > > this. Maybe we can filter with depends on !TEGRA or > > > > !SND_HDA_ALIGNED_MMIO at the SOF Intel top-level instead? > > > > > > That doesn't sound much better than my approach, but could also work. > > > One idea that I had but did not manage to implement was to move out > > > the snd_hdac_aligned_read/write functions from the core hda code > > > into a separate file. I think that would be the cleanest solution, > > > as it decouples the problem from any drivers. > > > > Yeah, that's a tricky problem because of the reverse-selection, as > > usual... > > > > Another solution would be to just avoid byte/word access but use only > > long access, i.e. replace snd_hdac_chip_readb() with > > snd_hdac_chip_readl() with the aligned register and bit shift. > > The aligned access helper is needed only for the register that isn't > > aligned with 4 bytes offset. > > Ok, so basically open-coding the aligned access to RIRBSTS? > That sounds like a much nicer workaround. So in place of > > sd_status = snd_hdac_stream_readb(s, SD_STS); > dev_vdbg(bus->dev, "stream %d status 0x%x\n", > s->index, sd_status); > snd_hdac_stream_writeb(s, SD_STS, sd_status); > > I suppose one could just readl/writel SOF_HDA_ADSP_REG_CL_SD_CTL > and print the shifted value, right? Yes. > While I know nothing about the underlying requirements, I wonder > about two things that stick out to me: > > 1. the existing code just writes back the same byte it has read. If > this write has no side-effects, why write it at all? OTOH, if it has > side-effects, isn't the aligned implementation of writing the whole > word in snd_hdac_aligned_write() fundamentally flawed? The aligned read/write does already the whole 4-bytes read/write, so it should work. But we need confirmation with the actual hardware. > 2. Doesn't the read-modify-write cycle in snd_hdac_aligned_write() > need locking to work correctly? The helper doesn't guarantee the atomic write by itself, so a lock would be required in the caller side if needed. Luckily there aren't many places calling the unaligned access. thanks, Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
