Am Freitag, den 16.01.2015, 14:42 +0200 schrieb Peter Ujfalusi: > On 01/16/2015 12:15 PM, Thomas Niederprüm wrote: > > Am Freitag, den 16.01.2015, 11:15 +0200 schrieb Peter Ujfalusi: > >> On 01/16/2015 12:28 AM, Thomas Niederprüm wrote: > >>> This patch fixes faulty behaviour in a setup where the input clock for > >>> the SRG is fed through the CLKR pin but the McBSP is configured to be > >>> master (SND_SOC_DAIFMT_CBS_CFS). In that case of course CLKR must not be > >>> configured as output pin. Otherwise the input clock is messed up > >>> horribly. The same reasoning applies if CLKX is configured as input for > >>> the SRG. > >> > >> If CLKX/CLKR is used as input clock for McBSP then the CBS_CFS is not valid. > >> In this case you need to use CBM_CFS. > >> > > The setup I am using is the following: McBSP is driving an external i2s > > DAC as master by supplying CLKX and FSX and DX. The DAC only supports > > i2s slave mode. For synchronization the DAC and the McBSP should share > > the same master/reference clock (CLKM). Since I don't need the receive > > path of the McBSP anyway for the DAC I can use the CLKR pin to insert > > the CLKM as input to the SRG. I think in this scenario CBS_CFS is valid > > since the McBSP acts as master (for the transmit path) > > Unfortunately the omap-mcbsp driver only supports synchronous configuration > for tx/rx (since almost all McBSP instance can only be used this way). The > first stream will configure both tx and rx to have the same properties. Even > if you are using McBSP1 which has separate FSX and FSR lines, the driver does > not have support for this. > From HW point of view this configuration is valid (not something I would > expect in any product). I don't think there are or will be other designs than > your using this mode... But, if you add some comment around the masking of > CLKXM and CLKRM bits that would be great. Do you mean adding it to the commit message or to the code? or both? > Just shortly why and also note that the set_dai_sysclk() _need_ to be called > after set_dai_fmt() to get the configuration you expect to see. > > > It might be more common to use the CKLS pin to inject the reference > > clock, but the beagleboard-xm I am using already hard wired this to the > > built-in twl4030 codec which makes it unusable. > > If you don't use the twl4030 the 256FS line should be floating, we are using > CBM_CFM for the twl4030 card which means that the 256FS is not enabled -> the > line is floating. > It should be safe to use the CLKS, but it is not rooted to any pin :( > Or remove the resistor form the line and connect your sync clock instead. I considered that for a moment as well, but it seemed hack-ish to me. I have to live with whatever can be muxed to the expansion headers of the beagle-xm and with that boundary condition using the CLKR seemed to be the most elegant solution. Also I gain the benefit that the twl4030 remains usable. > > >>> > >>> Signed-off-by: Thomas Niederprüm <niederp@xxxxxxxxxxxxxxxx> > >>> --- > >>> sound/soc/omap/omap-mcbsp.c | 4 ++++ > >>> 1 file changed, 4 insertions(+) > >>> > >>> diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c > >>> index bd3ef2a..c89f562 100644 > >>> --- a/sound/soc/omap/omap-mcbsp.c > >>> +++ b/sound/soc/omap/omap-mcbsp.c > >>> @@ -530,8 +530,12 @@ static int omap_mcbsp_dai_set_dai_sysclk(struct snd_soc_dai *cpu_dai, > >>> > >>> case OMAP_MCBSP_SYSCLK_CLKX_EXT: > >>> regs->srgr2 |= CLKSM; > >>> + regs->pcr0 |= SCLKME; > >>> + regs->pcr0 &= ~CLKXM; > >>> + break; > >>> case OMAP_MCBSP_SYSCLK_CLKR_EXT: > >>> regs->pcr0 |= SCLKME; > >>> + regs->pcr0 &= ~CLKRM; > >>> break; > >>> default: > >>> err = -ENODEV; > >>> > >> > >> > > > > -- Thomas Niederprüm TU Kaiserslautern FB Physik (AG Ott) Erwin-Schrödinger-Str. 46/431 67663 Kaiserslautern Tel.: 0631 205 2387 Fax: 0631 205 3906 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
