On Mon, Aug 03, 2020 at 04:04:23PM +0800, Shengjiu Wang wrote: > > > clock generation. The TCSR.TE is no need to enabled when only RX > > > is enabled. > > > > You are correct if there's only RX running without TX joining. > > However, that's something we can't guarantee. Then we'd enable > > TE after RE is enabled, which is against what RM recommends: > > > > # From 54.3.3.1 Synchronous mode in IMX6SXRM > > # If the receiver bit clock and frame sync are to be used by > > # both the transmitter and receiver, it is recommended that > > # the receiver is the last enabled and the first disabled. > > > > I remember I did this "ugly" design by strictly following what > > RM says. If hardware team has updated the RM or removed this > > limitation, please quote in the commit logs. > > There is no change in RM and same recommandation. > > My change does not violate the RM. The direction which generates > the clock is still last enabled. Using Tx syncing with Rx clock for example, T1: arecord (non-stop) => set RE T2: aplay => set TE then RE (but RE is already set at T1) Anything that I am missing? > > > + if (!sai->synchronous[TX] && sai->synchronous[RX] && !tx) { > > > + regmap_update_bits(sai->regmap, FSL_SAI_xCSR((!tx), ofs), > > > + FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE); > > > + } else if (!sai->synchronous[RX] && sai->synchronous[TX] && tx) { > > > + regmap_update_bits(sai->regmap, FSL_SAI_xCSR((!tx), ofs), > > > + FSL_SAI_CSR_TERE, FSL_SAI_CSR_TERE); > > > > Two identical regmap_update_bits calls -- both on !tx (RX?) > The content for regmap_update_bits is the same, but the precondition > is different. > The first one is for tx=false and enable TCSR.TE. (TX generate clock) > The second one is for tx=true and enable RSCR.RE (RX generate clock) Why not merge them? + if ((!sai->synchronous[TX] && sai->synchronous[RX] && !tx) || + ((!sai->synchronous[RX] && sai->synchronous[TX] && tx) {