Ard: IIRC eMMC2 is a better SDHCI-like controller. It supports more high-speed modes (e.g. 1.8V ones), resulting in better I/O performance,

A
From: Ard Biesheuvel <ard.biesheuvel@arm.com>
Sent: Wednesday, January 6, 2021 3:11 AM
To: Jeremy Linton <jeremy.linton@arm.com>; devel@edk2.groups.io <devel@edk2.groups.io>
Cc: leif@nuviainc.com <leif@nuviainc.com>; pete@akeo.ie <pete@akeo.ie>; samer.el-haj-mahmoud@arm.com <samer.el-haj-mahmoud@arm.com>; Andrei Warkentin <awarkentin@vmware.com>
Subject: Re: [PATCH v4 0/7] rpi4: Enable eMMC2 controller
 
On 1/5/21 5:34 PM, Jeremy Linton wrote:
> The rpi4 has a secondary SD controller at offset
> 0xfe340000. This controller appears to be a mostly
> compliant SDHCI controller (a newer more bugfree
> Arasan?). So the existing Arasan driver should be
> bound to it. This allows the rpi4 to boot
> with its normal eMMC2->SD card, Arasan->wifi
> configuration that is described in the Linux DT.
>

Could you please explain why this is an advantage? Is it related to ACPI
OSes not needing to change pinmuxing etc?


> To achieve this, it appears we should be tweaking
> some of the expansion gpios, and probably telling
> the firmware to power everything up. To do that
> the vpu mailbox headers are synced with a more recent
> list of the mailbox commands, then the rpi
> firmware dxe is extended to support some futher
> gpio/power commands. Once that is complete we tweak
> the arasan driver to use an alternate register base,
> add a workaround for a known clock crossing bug, and
> set the card voltage.
>
> Of note, this set does _NOT_ change the HID/CID's
> and add the additional eMMC2 controller to the
> DSDT table. That remains an open item waiting
> for a proper set of device ids.
>
> v3->v4: Commit message tweaks, variable rename.
> v1->v3: Use some mailbox defines rather than opencoded constants
>
> Jeremy Linton (7):
>   Platform/RaspberryPi: Update VPU mailbox constants
>   Platform/RaspberryPi: Add further mailbox helpers
>   Platform/RaspberryPi: Split MMC register definitions
>   Platform/RaspberryPi/Arasan: Add write delay and voltage/clock config
>   Platform/RaspberryPi/Arasan: Select the correct base frequency
>   Platform/RaspberryPi: Power up SD, and tweak GPIOs
>   Platform/RaspberryPi: Correct device path removal.
>
>  .../Drivers/ArasanMmcHostDxe/ArasanMmcHostDxe.c    | 131 ++++++++---
>  .../Drivers/ArasanMmcHostDxe/ArasanMmcHostDxe.h    |   1 +
>  Platform/RaspberryPi/Drivers/ConfigDxe/ConfigDxe.c |   7 +
>  .../Drivers/RpiFirmwareDxe/RpiFirmwareDxe.c        | 240 ++++++++++++++++++++-
>  .../RaspberryPi/Include/IndustryStandard/RpiMbox.h |  94 +++++++-
>  .../RaspberryPi/Include/Protocol/RpiFirmware.h     |  25 +++
>  .../Library/PlatformBootManagerLib/PlatformBm.c    |   2 +-
>  .../Bcm283x/Include/IndustryStandard/Bcm2836Sdio.h |  42 ++--
>  8 files changed, 484 insertions(+), 58 deletions(-)
>