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Revert r351218 (by manu). While the changes in r351218 appear to be (and

Browse Source 
should be) correct, they lead to the eMMC on a Beaglebone failing to work
in some situations.

The TI sdhci hardware is kind of strange.  The first device inherently
supports 1.8v and 3.3v and the abililty to switch between them, and the
other two devices must be set to 1.8v in the sdhci power control register to
operate correctly, but doing so actually makes them run at 3.3v (unless an
external level-shifter is present in the signal path).  Even the 1.8v on the
first device may actually be 3.3v (or any other value), depending on what
voltage is fed to the VDDS1-VDDS7 power supply pins on the am335x chip.

Another strange quirk is that the convention for am335x sdhci drivers in
linux and uboot and the am335x boot ROM seems to be to set the voltage in
the sdhci capabilities register to 3.0v even though the actual voltage is
3.3v.  Why this is done is a complete mystery to me, but it seems to be
required for correct operation.

If we had complete modern support for the am335x chip we could get the
actual voltages from the FDT data and the regulator framework.  But our
am335x code currently doesn't have any regulator framework support.
Reverting to the prior code will get the popular Beaglebone boards working
again.

This is part of the fix for PR 241301, but also requires r353651 for a
complete fix.

PR:		241301
Discussed with: manu
This commit is contained in:
Ian Lepore 2019-10-16 16:19:21 +00:00
parent 49dfdf633a
commit d436d6e96f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=353652
1 changed files with 10 additions and 12 deletions
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22
sys/arm/ti/ti_sdhci.c
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@ -482,14 +482,15 @@ ti_sdhci_hw_init(device_t dev)
* The attach() routine has examined fdt data and set flags in
* slot.host.caps to reflect what voltages we can handle. Set those
* values in the CAPA register. The manual says that these values can
* only be set once, and that they survive a reset so unless u-boot didn't
* set this register this code is a no-op.
* only be set once, "before initialization" whatever that means, and
* that they survive a reset. So maybe doing this will be a no-op if
* u-boot has already initialized the hardware.
*/
regval = ti_mmchs_read_4(sc, MMCHS_SD_CAPA);
if (sc->slot.host.caps & MMC_OCR_LOW_VOLTAGE)
regval |= MMCHS_SD_CAPA_VS18;
if (sc->slot.host.caps & (MMC_OCR_320_330 | MMC_OCR_330_340))
regval |= MMCHS_SD_CAPA_VS33;
if (sc->slot.host.caps & (MMC_OCR_290_300 | MMC_OCR_300_310))
regval |= MMCHS_SD_CAPA_VS30;
ti_mmchs_write_4(sc, MMCHS_SD_CAPA, regval);
/* Set initial host configuration (1-bit, std speed, pwr off). */
@ -523,20 +524,17 @@ ti_sdhci_attach(device_t dev)
}
/*
* The hardware can inherently do dual-voltage (1p8v, 3p3v) on the first
* The hardware can inherently do dual-voltage (1p8v, 3p0v) on the first
* device, and only 1p8v on other devices unless an external transceiver
* is used. The only way we could know about a transceiver is fdt data.
* Note that we have to do this before calling ti_sdhci_hw_init() so
* that it can set the right values in the CAPA register, which can only
* be done once and never reset.
*/
if (OF_hasprop(node, "ti,dual-volt")) {
sc->slot.host.caps |= MMC_OCR_LOW_VOLTAGE | MMC_OCR_320_330 | MMC_OCR_330_340;
} else if (OF_hasprop(node, "no-1-8-v")) {
sc->slot.host.caps |= MMC_OCR_320_330 | MMC_OCR_330_340;
} else
sc->slot.host.caps |= MMC_OCR_LOW_VOLTAGE;
sc->slot.host.caps |= MMC_OCR_LOW_VOLTAGE;
if (sc->mmchs_clk_id == MMC1_CLK || OF_hasprop(node, "ti,dual-volt")) {
sc->slot.host.caps |= MMC_OCR_290_300 | MMC_OCR_300_310;
}
/*
* Set the offset from the device's memory start to the MMCHS registers.