[PATCH] imx8mm_beacon: Enable HS400 on MMC controller

[ZHIZHIKIN Andrey]

> -----Original Message-----
> From: Adam Ford <aford173 at gmail.com>
> Sent: Saturday, December 5, 2020 4:01 PM
> To: ZHIZHIKIN Andrey <andrey.zhizhikin at leica-geosystems.com>
> Cc: u-boot at lists.denx.de; aford at beaconembedded.com
> Subject: Re: [PATCH] imx8mm_beacon: Enable HS400 on MMC controller
> 
> 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.

OK, got it! Since you've introduced it for a specific derivative and you know that
from the size perspective it fits - then I believe it is OK to have them enabled. 

> 
> 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.

For EVK configs I would leave SPL configs OFF.

> 
> 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

-- andrey