IMX8MM SD UHS support
Tim Harvey
tharvey at gateworks.com
Wed Dec 30 17:54:03 CET 2020
On Wed, Dec 30, 2020 at 1:30 AM ZHIZHIKIN Andrey
<andrey.zhizhikin at leica-geosystems.com> wrote:
>
> Hello Tim,
>
> > -----Original Message-----
> > From: Tim Harvey <tharvey at gateworks.com>
> > Sent: Wednesday, December 30, 2020 12:22 AM
> > To: ZHIZHIKIN Andrey <andrey.zhizhikin at leica-geosystems.com>; Peng Fan
> > <Peng.Fan at nxp.com>; u-boot <u-boot at lists.denx.de>
> > Cc: Fabio Estevam <festevam at gmail.com>; Stefano Babic <sbabic at denx.de>
> > Subject: IMX8MM SD UHS support
> >
> >
> > Greetings,
> >
> > In 50b1a69cee0d ("ARM: dts: imx8m: add UHS or HS400/HS400ES
> > properties") u-boot dt props were added to enable UHS and HS400 on a couple of
> > IMX8MM boards including the imx8mm-evk and in the subsequent patch
> > enabled the config items.
> >
> > While I see this making a huge difference for eMMC performance in U-Boot I find
> > it doesn't do anything for microSD performance.
> >
> > The issue appears to be that sd_get_capabilities() is not appropriately detecting
> > UHS speeds on cards that appropriately detect as SDR104/DDR50 in Linux:
> >
> > u-boot=> mmc info
> > Device: FSL_SDHC
> > Manufacturer ID: 1b
> > OEM: 534d
> > Name: 00000
> > Bus Speed: 50000000
> > Mode: SD High Speed (50MHz)
> > card capabilities: widths [4, 1] modes [MMC legacy, SD High Speed (50MHz)] ^^^^
> > no SDR104 detected for this card host capabilities: widths [4, 1] modes [MMC
> > legacy, MMC High Speed (26MHz), SD High Speed (50MHz), MMC High Speed
> > (52MHz), UHS DDR50 (50MHz), UHS SDR104 (208MHz)] Rd Block Len: 512 SD
> > version 3.0 High Capacity: Yes
> > Capacity: 14.9 GiB
> > Bus Width: 4-bit
> > Erase Group Size: 512 Bytes
> >
> > The same card in Linux shows the following upon insertion and performance tests
> > show that it is operating at SDR104 speeds:
> > mmc1: new ultra high speed SDR104 SDHC card at address 0001
> >
> > I haven't found very good documentation on the SD switch settings to
> > understand if something is wrong in the U-Boot implementation of of
> > sd_get_capabilities() and I suppose it also could be an issue in sdhci-esdhc-imx.c.
>
> In order to SD Card to operate in High Speed modes, the signaling voltage should
> be switched from 3v3 to 1v8. Otherwise, higher clock rates cannot be applied and
> card continues to be operating with lower speed modes.
>
> Have you verified that the NVCC_SD2 is switched to 1v8 in your case?
>
> Since you did not indicate which board you're using - it is hard for me to suggest
> on how measure this voltages. If you're using i.MX8M Mini EVK, then you can
> verify this by measuring the voltage at the test point called "NVCC_SD2" located
> on the Core Module in the PMIC area.
>
> >
> > Any ideas where to look?
> >
> > Anyone see SDR104 cards being detected properly for other platforms?
>
> Yes, in fact I do see that SD Card is recognized for me as UHS SD104:
>
> u-boot=> mmc dev 1
> Run CMD11 1.8V switch
> switch to partitions #0, OK
> mmc1 is current device
> u-boot=> mmc info
> Device: FSL_SDHC
> Manufacturer ID: 9f
> OEM: 5449
> Name: 00000
> Bus Speed: 200000000
> Mode: UHS SDR104 (208MHz)
> Rd Block Len: 512
> SD version 3.0
> High Capacity: Yes
> Capacity: 29.8 GiB
> Bus Width: 4-bit
> Erase Group Size: 512 Bytes
>
> Please pay attention to the output, which says "Run CMD11 1.8V switch".
>
> Do you also observe the same output?
>
Andrey,
I did mention that I am using the imx8mm-evk. When I saw that my
custom board was having issues with sd_get_capabilities() I switched
to the imx8mm-evk and confirmed my findings there.
I'm using master (ab865a8ee5c1) with imx8mm_evk_defconfig running on
an imx8mm-evk board configured via dip switches to boot from eMMC. I
have a SDR104 microSD which detects and operates as such in Linux and
this is what I see in U-Boot:
U-Boot SPL 2021.01-rc4-00029-gab865a8 (Dec 30 2020 - 08:29:24 -0800)
Normal Boot
WDT: Started with servicing (60s timeout)
Trying to boot from MMC2
U-Boot 2021.01-rc4-00029-gab865a8 (Dec 30 2020 - 08:29:24 -0800)
CPU: Freescale i.MX8MMQ rev1.0 at 1200 MHz
Reset cause: POR
Model: FSL i.MX8MM EVK board
DRAM: 2 GiB
WDT: Started with servicing (60s timeout)
MMC: FSL_SDHC: 1, FSL_SDHC: 2
Loading Environment from MMC... OK
In: serial
Out: serial
Err: serial
Net: eth0: ethernet at 30be0000
Hit any key to stop autoboot: 0
u-boot=> mmc dev 1
Run CMD11 1.8V switch
switch to partitions #0, OK
mmc1 is current device
u-boot=> mmc info
Device: FSL_SDHC
Manufacturer ID: 1b
OEM: 534d
Name: 00000
Bus Speed: 50000000
Mode: SD High Speed (50MHz)
Rd Block Len: 512
SD version 3.0
High Capacity: Yes
Capacity: 14.9 GiB
Bus Width: 4-bit
Erase Group Size: 512 Bytes
You can see that the 1.8V switch succeeds and the card is recognized
as high-speed but does not show the SDR104 capability.
Adding the following debugging:
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index a6394bc..663bf3d 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -1365,6 +1365,10 @@ static int sd_get_capabilities(struct mmc *mmc)
return 0;
sd3_bus_mode = __be32_to_cpu(switch_status[3]) >> 16 & 0x1f;
+printf("%s %s sd3_bus_mode=0x%x\n", __func__, mmc->dev->name, sd3_bus_mode);
+for (int i = 0; i < 16; i++) {
+ printf("switch_status[%d]=0x%08x\n", i, switch_status[i]);
+}
if (sd3_bus_mode & SD_MODE_UHS_SDR104)
mmc->card_caps |= MMC_CAP(UHS_SDR104);
if (sd3_bus_mode & SD_MODE_UHS_SDR50)
Shows:
u-boot=> mmc dev 1
Run CMD11 1.8V switch
sd_get_capabilities mmc at 30b50000 sd3_bus_mode=0x3
switch_status[0]=0x0180c800
switch_status[1]=0x01800180
switch_status[2]=0x01800180
switch_status[3]=0x00000380
switch_status[4]=0x00000001
switch_status[5]=0x00000000
switch_status[6]=0x00000000
switch_status[7]=0x00000000
switch_status[8]=0x00000000
switch_status[9]=0x00000000
switch_status[10]=0x00000000
switch_status[11]=0x00000000
switch_status[12]=0x00000000
switch_status[13]=0x00000000
switch_status[14]=0x00000000
switch_status[15]=0x00000000
switch to partitions #0, OK
mmc1 is current device
What board and U-Boot sha/config are you using? Do you have the
ability to confirm my findings on an imx8mm-evk?
The code in sd_get_capabilities differs greatly from what Linux does.
I don't have documentation on the MMC switch settings so I can't
understand if what is being done is correct but it is interesting that
your card is detected as SDR104.
The card I'm using above is a Samsung PRO 16GB but I've repeated the
findings on a dozen cards that support either SD104 or DDR50 (again,
proven in Linux).
Best regard,
Tim
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