On 24/04/2016 12:14 p.m., Dong Aisheng wrote:
Hi Adrian,
Thanks for the review first.
On Fri, Apr 22, 2016 at 7:43 PM, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
On 15/04/16 20:29, Dong Aisheng wrote:
Handle host and regulator signal voltage switch separately.
Move host signal voltage switch code into a separated function
sdhci_do_signal_voltage_switch() first, the following patches will
remove the regulator voltage switch code and use the common
mmc_regulator_set_vqmmc() instead.
You have changed the order that things are done.
Yes, the oder changes a bit that we always do controller voltage switch first.
I suppose the order is irrelevant here since i don't recall any
requirement from card.
Actually the original order is also a bit mass.
e.g.
For MMC_SIGNAL_VOLTAGE_330, switch controller first, then vqmmc.
But for MMC_SIGNAL_VOLTAGE_180, switch vqmmc first, then controller.
It looks to us the original one also order irrelevant.
There is no way to know
what that will break, so let's not do that. What about just changing
regulator_set_voltage() to mmc_regulator_set_vqmmc()?
Currently what i can think out VIO switch using are three cases: (Pls
help add if any)
1) Both host IO and card IO use external vqmmc to do switch
(e.g eMMC 1.8V DDR/HS200/HS400 mode)
eMMC has no IO voltage switch protocol and requirement, so usually
board designed
using fixed 1.8V for eMMC and host IO.
Event it's switchable, it should be done in the first mmc_power_up().
Dynamical switch later may cause eMMC unable to work properly.
(We have been confirmed about this issue by many eMMC vendors
like Micron and Sandisk. I'm not sure if any exceptions in the community
still doing VIO dynamical switch for eMMC, if yes, please help share
the experience!).
Event some people still do dynamical IO switch for eMMC, since eMMC
spec has no requirement, so the order should also not care.
2) Host using controller IO switch while card using standard CMD (SD/SDIO3.0)
SD/SDIO 3.0 spec defines the standard IO switch process and using it's internal
regulator to do card IO voltage switch. It does not use external vqmmc
regulator.
So order irrelevant too.
3) Host using controller IO switch while card using external vqmmc
(special SDIO3.0 or eMMC)
I have met some special SDIO3.0 card like Broadcom WiFi which does not follow
the spec and using external regulator for card IO voltage.
Usually it's required to fix to 1.8v and also not order irrelevant.
For eMMC, refer to case 1), it should be fixed to 1.8v at power up.
So it looks all cases seems are not order required.
I don't agree that there is any way to know that other host controllers
are not affected. I don't want a repeat of sdhci_set_power().
Please instead send a patch for just using mmc_regulator_set_vqmmc()
in place of regulator_set_voltage().
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