[alsa-devel] [PATCH V1 2/3] ASoC: fsl_spdif: spba clk is needed by spdif device

[Nicolin Chen]

On Sat, Oct 10, 2015 at 05:03:07PM -0300, Fabio Estevam wrote:
> On Sat, Oct 10, 2015 at 7:26 AM, Shengjiu Wang
> <shengjiu.wang at freescale.com> wrote:
> 
> > I think spba clock should be used by the audio IP not DMA, because in same
> > situation the FSL_SSI doesn't need this clock.
> 
> According to this commit from FSL BSP, the SSI2 port on MX53 is
> connected to SPBA and needs the SPBA clock:
> 
> http://git.freescale.com/git/cgit.cgi/imx/linux-2.6-imx.git/commit/arch/arm/mach-mx5/clock.c?h=imx_2.6.35_maintain&id=2438f48431b7aff00a522502d5a6ea217ea133d9

Hmm, the detail of an SPBA issue is sometimes complicated due to
different fabric designs between SoCs. We cannot simply say that
a DMA access for an IP under the Shared Peripheral Bus requires
SPBA clock or not unless the hardware team clearly demands that.

However, as an arbiter, the SPBA must be outside any of those IPs
and tied to the SDMA in order to balancing memory access between
the SDMA and a co-existing CPU. The question is whether we treat
it as a part of an IP wrapper or a part of the SDMA.

Therefore, unless a CPU access would fail even *without any SDMA
access being launched*, it sounds fair to me to put it into the
DMA code.