On Tue, 25 May 2021, at 22:26, Joel Stanley wrote: > On Tue, 25 May 2021 at 09:48, Steven Lee <steven_lee@xxxxxxxxxxxxxx> wrote: > > > > The 05/25/2021 15:55, Joel Stanley wrote: > > > When I was testing on my A2 EVB I saw this: > > > > > > [ 1.436219] sdhci-aspeed 1e750100.sdhci: Requested out of range > > > phase tap 192 for 9 degrees of phase compensation at 1562500Hz, > > > clamping to tap 15 > > > [ 1.450913] sdhci-aspeed 1e750100.sdhci: Requested out of range > > > phase tap 963 for 45 degrees of phase compensation at 1562500Hz, > > > clamping to tap 15 > > > > > > Do you know what is happening there? > > > > > > > Per MMC spec, eMMC bus speed is set as legacy mode(0~26MHz) at startup of > > eMMC initializtion flow. Clock phase calculation is triggered in set_clock() > > and it calculates taps based on phase_deg(<9>, <225>) in the dts file and the > > current speed(1562500Hz), which causes the warning message you mentioned. > > As the phase_deg in the dts file should be calculated with 100MHz. > > > > https://lkml.org/lkml/2021/5/24/95 > > > > But after some initialization flow, eMMC bus speed will be set to > > correct speed(100MHz). > > Clock phase calculation will be triggered again to get correct taps. > > Thanks for the explanation. I added another debug print and I can see > it doing what you describe: > > [ 1.465904] sdhci-aspeed 1e750100.sdhci: Requested out of range > phase tap 192 for 9 degrees of phase compensation at 1562500Hz, > clamping to tap 15 > [ 1.480598] sdhci-aspeed 1e750100.sdhci: rate 1562500 phase 9 tap 15 > [ 1.490316] sdhci-aspeed 1e750100.sdhci: Requested out of range > phase tap 963 for 45 degrees of phase compensation at 1562500Hz, > clamping to tap 15 > [ 1.505077] sdhci-aspeed 1e750100.sdhci: rate 1562500 phase 45 tap 15 > [ 1.515059] sdhci-aspeed 1e750100.sdhci: rate 100000000 phase 9 tap 3 > [ 1.524886] sdhci-aspeed 1e750100.sdhci: rate 100000000 phase 45 tap 15 > [ 1.534904] sdhci-aspeed 1e750100.sdhci: rate 100000000 phase 9 tap 3 > [ 1.544713] sdhci-aspeed 1e750100.sdhci: rate 100000000 phase 45 tap 15 > > We should change the "out of range" message to be dev_dbg, as it is > expected on a normal boot. I would think the issue is rather that we shouldn't be applying a phase correction for a bus speed that isn't what the correction was specified for. Let me look at this a bit further. Andrew
