[PATCH] imx8mm_beacon: Enable HS400 on MMC controller

[Adam Ford]

On Sat, Dec 5, 2020 at 8:54 AM ZHIZHIKIN Andrey
<andrey.zhizhikin at leica-geosystems.com> wrote:
>
> Hello Adam,
>
> > -----Original Message-----
> > From: U-Boot <u-boot-bounces at lists.denx.de> On Behalf Of Adam Ford
> > Sent: Saturday, December 5, 2020 2:00 AM
> > To: u-boot at lists.denx.de
> > Cc: aford at beaconembedded.com; Adam Ford <aford173 at gmail.com>
> > Subject: [PATCH] imx8mm_beacon: Enable HS400 on MMC controller
> >
> >
> > The i.MX8MM is capable of HS400.  Enable it in both U-Boot and SPL for faster
> > throughput.
>
> I'm not quite sure if those high-speed modes would be required to be enabled for
> SPL...
There are separate SPL flags, so we could leave them off.

>
> Even though the support for those modes is provided in SPL build, there might be
> a little benefit of having it enabled as the only thing SPL would need to fetch from
> storage medias would be U-Boot itself, and the difference in access time between
> high speed modes enabled or disabled for this task is quite negligible. The downside
> there would rather be an increase in SPL size to accommodate enabled code paths.
>
> I was contemplating myself to have those included, but decided to op-out from it
> as I could not justify the benefit of it.
>
> Do you see any particular use-case where it would be beneficial to enable those modes
> in SPL? If so - can you please share them, as if it would turn out to be beneficial - I might
> also turn them on in EVK configs.

I turned them on because I could and it fit into SPL.  In theory the
impy could be deactivated for people who don't have the room.  I
didn't do any time measurements so I don't know of the higher speed
made it load u-boot any faster since it takes a little more time to do
the extra initialization, I can see the argument to leave them off.

Maybe it's best to default the configs to leave them off in SPL, and
let people decide on what's best for their boards.  For the Beacon
board, I'll probably leave it on, but if SPL size constraints become
an issue, I might turn them off later.

adam
>
> >
> > Signed-off-by: Adam Ford <aford173 at gmail.com>
> >
> > diff --git a/configs/imx8mm_beacon_defconfig
> > b/configs/imx8mm_beacon_defconfig index c5d331f617..49d5453078 100644
> > --- a/configs/imx8mm_beacon_defconfig
> > +++ b/configs/imx8mm_beacon_defconfig
> > @@ -70,6 +70,13 @@ CONFIG_DM_I2C=y
> >  CONFIG_SYS_I2C_MXC=y
> >  CONFIG_DM_MMC=y
> >  CONFIG_SUPPORT_EMMC_BOOT=y
> > +CONFIG_MMC_IO_VOLTAGE=y
> > +CONFIG_SPL_MMC_IO_VOLTAGE=y
> > +CONFIG_MMC_UHS_SUPPORT=y
> > +CONFIG_SPL_MMC_UHS_SUPPORT=y
> > +CONFIG_MMC_HS400_ES_SUPPORT=y
> > +CONFIG_MMC_HS400_SUPPORT=y
> > +CONFIG_SPL_MMC_HS400_SUPPORT=y
> >  CONFIG_FSL_USDHC=y
> >  CONFIG_PHYLIB=y
> >  CONFIG_PHY_ATHEROS=y
> > --
> > 2.25.1
>
> -- andrey