imx6ull define sd card speed/clock frequency

[alampret]

Hi,

I've created a custom imx6ull board and therefore copied dts from imx6ul-14x14 evk board.

In this dts file, there are 3 pinctrl for "default", 100MHz and 200MHz.

Current result of cat /sys/kernel/debug/mmc0/ios is:

clock: 50000000 Hz

actual clock: 49500000 Hz

vdd: 21 (3.3 ~ 3.4 V)

bus mode: 2 (push-pull)

chip select: 0 (don't care)

power mode: 2 (on)

bus width: 2 (4 bits)

timing spec: 2 (sd high-speed)

signal voltage: 0 (3.30 V)

driver type: 0 (driver type B)

How is it possible to increase clock and speed? Which settings have to be changed?

Currently, read from sd card is quite slow.

Thx!

Alexander

[igorpadykov]

Hi Alexander

linux driver selects maximum speed automatically based

on sd csd register maximum data transfer rate, so for example sd1 port

has 3 pinctrl for "default", 100MHz and 200MHz. Note for such high rates

power cycling is needed, provided by SD1_nRST.

Best regards
igor
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[alampret]

Ok, clear.

And what about BOOT_CFG1? Does it makes sense to change [2,3] to increase speed? If yes, is it possible to test these settings without ordering a new pcb? Like in fuse or any other settings?

[igorpadykov]

yes one can use USDHC boot eFUSE SD/MMC speed mode, settings.

Check Boot Chapter Reference Manual.

[alampret]

Thank you for your answer.

How do I set the eFUSE? Without destroying all other parts :smileywink:

All boot parameters are defined by resistors on boot (LCD_... Pins) but SDR50 or SDR104 has to be set by eFUSE.

Thx,

Alexander

[igorpadykov]

Hi Alexander

please create new thread for each new topic

Best regards
igor