[dimerr]

The SD card on a gwell AK3918EV200 camera never answered in U-Boot (Card did not respond to voltage select! : -110). Every response came back all zeros with RESPEND set, i.e. CMD held low, while Linux on the same board read the card.

I set the registers Linux leaves (from devmem) in U-Boot one at a time on the camera. The card answers only with both of these:

• GPIO 34 low, with its pad a GPIO. GPIO 34 is wifi_en in the EV200 reference board's DT, on the pad that is otherwise SD DAT1. The boot ROM leaves that pad's field (0x080000DC 11:10) at 11. The SD driver now muxes the pad to GPIO and drives it low (EV200 only).
• SPI0 pads 35/36 at function 2 (0xDC 13:12 = 10), as the EV200 DT's spiflash_pins and Linux set them, instead of the gwell vendor U-Boot's 0x3003 (11). ak_sflash now writes 0x2003 on EV200.

Tested on the camera: the card is found at boot with no manual writes, flash reads are stable, the kernel boots from flash, and reset works. In qemu-hisilicon (no pin model): SD and flash still work on ak3918ev200, and all six images build.

GPIO 34 comes from the reference design. An EV200 board that uses GPIO 34 for something else would need a different value.

[qodo-free-for-open-source-projects]

PR Summary by Qodo

anyka: Restore SD card responses on the gwell AK3918EV200

🐞 Bug fix 📝 Documentation 🕐 20-40 Minutes

AI Description

• Drive EV200 GPIO 34 low so the gwell camera’s SD card can respond.

Diagram

graph TD
  Flash["SPI flash probe"] --> SPI["SPI pad function"] --> Mux["Shared pin mux"] --> Card(["SD card"])
  MMC["MMC host init"] --> GPIO["GPIO 34 low"] --> Card
  MMC --> Mux

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High-Level Assessment

The following are alternative approaches to this PR:

1. Make GPIO 34 board-specific

• ➕ Avoids driving a pin that another EV200 board may use differently.
• ➖ Requires board-level configuration plumbing for a currently fixed, non-DM MMC driver.

Recommendation: The driver-local, EV200-gated changes are appropriate for the tested camera and preserve EV300/EV330 behavior. GPIO 34 is a reference-board assumption, however; make that pin board-configurable if additional EV200 boards with different wiring are supported.

Files changed (3) +37 / -8

Bug fix (2) +28 / -6

ak_mmc.cMux EV200 pad 34 to GPIO and drive it low +17/-1

Mux EV200 pad 34 to GPIO and drive it low

• MMC host initialization clears pad 34’s function field, then configures GPIO 34 as a low output. The behavior is limited to EV200 builds and also applies when the host is reinitialized.

drivers/mmc/ak_mmc.c

ak_sflash.cSelect EV200 SPI0 pad function 2 +11/-5

Select EV200 SPI0 pad function 2

• SPI flash initialization now clears and sets the EV200 pad field to 0x2003 instead of setting 0x3003. EV300 retains its existing set-only behavior, and EV330 remains unchanged.

drivers/mtd/spi/ak_sflash.c

Documentation (1) +9 / -2

CLAUDE.mdDocument the EV200 pin settings required for SD +9/-2

Document the EV200 pin settings required for SD

• Records the EV200 SPI pad function and GPIO 34 setting, including why the gwell camera needs both for SD responses.

CLAUDE.md

[qodo-free-for-open-source-projects]

Code Review by Qodo

🐞 Bugs (0) 📘 Rule violations (0) 📎 Requirement gaps (0)

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