Messages in this thread | | | Date | Wed, 09 Sep 2015 15:04:11 +0200 | From | Olliver Schinagl <> | Subject | Almost certainly confirmed, sun7i-a20 does not support 8 bit mmc. |
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Hey all,
After experimenting with a Micron eMMC chip, I made some interesting finds I wanted to share with you all.
For a while now, some had hopes or guessed that the A20 could have support for 8 bit wide bused on the SDC2. Reason for thinking this was, because the sun7i uses the same IP as the sun5i which does support 8 bit wide eMMC. The usermanual does mention 1/4/8 bit data buses and jedec 4.3 support of the MMC spec. Unfortunately so far, it appears that the extra data pins have not been muxed out to the PC pads.
I used the following code to enable the extra pins on the A20: mmc2_pins_a: mmc2@0 { - allwinner,pins = "PC6", "PC7", "PC8", - "PC9", "PC10", "PC11"; + allwinner,pins = "PC6", "PC7", + "PC8", "PC9", "PC10", "PC11", + "PC12", "PC13", "PC14", "PC15";
and SUNXI_PIN(SUNXI_PINCTRL_PIN(C, 12), SUNXI_FUNCTION(0x0, "gpio_in"), SUNXI_FUNCTION(0x1, "gpio_out"), - SUNXI_FUNCTION(0x2, "nand0")), /* NDQ4 */ + SUNXI_FUNCTION(0x2, "nand0"), /* NDQ4 */ + SUNXI_FUNCTION(0x3, "mmc2")), /* D4 */ SUNXI_PIN(SUNXI_PINCTRL_PIN(C, 13), SUNXI_FUNCTION(0x0, "gpio_in"), SUNXI_FUNCTION(0x1, "gpio_out"), - SUNXI_FUNCTION(0x2, "nand0")), /* NDQ5 */ + SUNXI_FUNCTION(0x2, "nand0"), /* NDQ5 */ + SUNXI_FUNCTION(0x3, "mmc2")), /* D5 */ SUNXI_PIN(SUNXI_PINCTRL_PIN(C, 14), SUNXI_FUNCTION(0x0, "gpio_in"), SUNXI_FUNCTION(0x1, "gpio_out"), - SUNXI_FUNCTION(0x2, "nand0")), /* NDQ6 */ + SUNXI_FUNCTION(0x2, "nand0"), /* NDQ6 */ + SUNXI_FUNCTION(0x3, "mmc2")), /* D6 */ SUNXI_PIN(SUNXI_PINCTRL_PIN(C, 15), SUNXI_FUNCTION(0x0, "gpio_in"), SUNXI_FUNCTION(0x1, "gpio_out"), - SUNXI_FUNCTION(0x2, "nand0")), /* NDQ7 */ + SUNXI_FUNCTION(0x2, "nand0"), /* NDQ7 */ + SUNXI_FUNCTION(0x3, "mmc2")), /* D7 */
which I think should be enough? Unfortunatly after booting i get the following:
[ 0.971642] sunxi-mmc 1c11000.mmc: smc 1 err, cmd 8, RTO !! [ 0.981346] sunxi-mmc 1c11000.mmc: smc 1 err, cmd 55, RTO !! [ 0.987873] sunxi-mmc 1c11000.mmc: smc 1 err, cmd 55, RTO !! [ 0.988704] sunxi-mmc 1c11000.mmc: smc 1 err, cmd 55, RTO !! [ 0.989531] sunxi-mmc 1c11000.mmc: smc 1 err, cmd 55, RTO !! [ 1.020574] mmc1: MAN_BKOPS_EN bit is not set (This I always get for some reason btw, so if somebody has a thought that'd be appreciated)
[ 1.024234] sunxi-mmc 1c11000.mmc: smc 1 err, cmd 8, RD EBE !! [ 1.024265] sunxi-mmc 1c11000.mmc: data error, sending stop command [ 1.024276] sunxi-mmc 1c11000.mmc: send stop command failed [ 1.024295] mmc1: switch to bus width 2 failed [ 1.028642] mmc1: new high speed MMC card at address 0001 [ 1.029133] mmcblk1: mmc1:0001 P1XXXX 3.60 GiB [ 1.031071] mmcblk1boot0: mmc1:0001 P1XXXX partition 1 16.0 MiB [ 1.031207] mmcblk1boot1: mmc1:0001 P1XXXX partition 2 16.0 MiB [ 1.032305] mmcblk1: p1 p2 p3
Hence, the controller fails to enable 8 bit mode. mmc1's ios confirms this afterwards: /sys/kernel/debug/mmc1# cat ios clock: 50000000 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: 1 (mmc high-speed) signal voltage: 0 (3.30 V)
On the upside, performance is pretty good however. Using a sequential dd test on the whole 4GB of storage to /dev/null and reading to a 3GB file from /dev/zero, I'm hitting 22 MB/s read and 13 MB/s write. The datasheet of the eMMC chip obviously has exotic values in the 75MB/s range, but compared to ~12 MB/s read/write from a regular 8gb 'class 10' SD card, and 4-6 MB/s read/write from the regular onboard NAND flash, this is pretty decent.
A photograph of the soldering handy work (not by me) can be seen at the linux-sunxi wiki [0].
Olliver
[0] http://linux-sunxi.org/File:Lime2_emmc.jpg
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