Hello Tim,
-----Original Message----- From: Tim Harvey tharvey@gateworks.com Sent: Wednesday, December 30, 2020 12:22 AM To: ZHIZHIKIN Andrey andrey.zhizhikin@leica-geosystems.com; Peng Fan Peng.Fan@nxp.com; u-boot u-boot@lists.denx.de Cc: Fabio Estevam festevam@gmail.com; Stefano Babic sbabic@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?
Best regards,
Tim
-- andrey