iMX6SLL-EVK SDIO 3.0 interface WiFi throughput is less

[pandivijayaraj]

Hi All,

I am interfacing an external WiFi module card supporting SDIO 3.0 with IMX6SLL-EVK host platform. IMX6SLL-EVK host is running Linux kernel 4.9.11 and driver is inserted properly into the kernel. The SDIO port used is uSDHC3.

I am attaching here the dmesg MMC logs during bootup with the WiFI card inserted

The SDIO port sattus information is given below.

               ubuntu@arm:~$ sudo cat /sys/kernel/debug/mmc2/ios
               clock: 208000000 Hz
               actual clock: 198000000 Hz
               vdd: 18 (3.0 ~ 3.1 V)
               bus mode: 2 (push-pull)
               chip select: 0 (don't care)
               power mode: 2 (on)
               bus width: 2 (4 bits)
               timing spec: 6 (sd uhs SDR104)
               signal voltage: 1 (1.80 V)
               driver type: 0 (driver type B)

I believe that WiFi card is detected in UHS SDR104 mode. But when I test WiFi transmit throughput, It is around 100Mbps only. It is similar to the SDIO 2.0 mode throughput observed in some laptop hosts.

I expect the transmit throughput to be more than atleast 200Mbps.

Is there any limitation in iMX6SLL-EVK performace. pls, let me know the problem in this scenario.

Also suggest some platforms supporting high throughput in SDIO 3.0 mode.

Regards,

Pandi Vijayaraj

[pandivijayaraj]

Hi Igor,

Thanks for the response. I have disabled the MMC_DEBUG which was causing some drop in throughput.

After this change throughput increased more to 170Mbps.

Also one more issue I am observing is that,  MMC Timeout waiting for Hardware interrupt. This is observed sometimes when throughput test is running and the SDIO slot becomes unresponsive. WiFi Card has to be reinserted into slot to restart the SDIO slot operation. The error log is below.

ubuntu@arm:~$ mmc2: Timeout waiting for hardware interrupt.

sdhci: =========== REGISTER DUMP (mmc2)===========

sdhci: Sys addr: 0xe4a00240 | Version:  0x00000002

sdhci: Blk size: 0x00000100 | Blk cnt:  0x00000061

sdhci: Argument: 0x9d9f0061 | Trn mode: 0x00000023

sdhci: Present:  0x01f8810e | Host ctl: 0x00000013

sdhci: Power:    0x00000002 | Blk gap:  0x00000080

sdhci: Wake-up:  0x00000008 | Clock:    0x0000001f

sdhci: Timeout:  0x0000008f | Int stat: 0x00000000

sdhci: Int enab: 0x107f110b | Sig enab: 0x107f110b

sdhci: AC12 err: 0x00000000 | Slot int: 0x00000302

sdhci: Caps:     0x07eb0000 | Caps_1:   0x8000b407

sdhci: Cmd:      0x0000353a | Max curr: 0x00ffffff

sdhci: Host ctl2: 0x00000088

sdhci: ADMA Err: 0x00000003 | ADMA Ptr: 0xec4d1204

sdhci: ===========================================

Regards,

Pandi Vijayaraj

[igorpadykov]

Hi Pandi

please try to test some SD 3.0 SDR104 card, not wifi as

wifi card throughput may be affected by other factors for example

environment noise conditions.

Best regards
igor