On Tue, 10 Sep 2019 09:52:13 +0200, Arnd Bergmann wrote:
On Tue, Sep 10, 2019 at 9:06 AM Takashi Iwai tiwai@suse.de 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@linux.intel.com 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:
- 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.
- 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