Gx Chip Driver (TOP)

can occur if status register is not cleared exactly once. 6. Debugging GX Drivers Without Vendor Support 6.1 Tools & Methods | Tool | Purpose | |------|---------| | devmem2 | Read/write raw registers (e.g., devmem2 0xF0000020 ) | | strace | Trace ioctl calls to DRM/V4L2 | | dmesg -w | Watch driver prints (enable with DYNAMIC_DEBUG ) | | cat /sys/kernel/debug/dri/*/state | DRM state | | gdb + KGDB | Kernel debugging over serial | 6.2 Common Errors & Fixes Error: gx_vpu: timeout waiting for interrupt → Check VPU clock (is it enabled?), firmware loaded? Try clk_enable(vpu_clk) .

VPU_REG_DEC_CTRL (0xF100_0000) VPU_REG_STATUS (0xF100_0004) // bit 0 = busy VPU_REG_DATA (0xF100_0008) // firmware mailbox Driver requests gx_vpu_fw.bin from /lib/firmware . Missing firmware → VPU fails to start. gx chip driver

echo 0x1f > /sys/module/gx_vpu/parameters/debug to enable verbose logging. Check cat /proc/interrupts | grep vpu for interrupt count. 4.4 I2C / SPI Drivers ( gx_i2c , gx_spi ) These are simple wrapper drivers around DesignWare IP or a custom bit-bang. The GX implementation often lacks proper clock gating or recovery on bus hang. can occur if status register is not cleared exactly once

gx_disp: failed to set mode → EDID read failed. Force mode via kernel param: video=HDMI-A-1:1920x1080@60 . Try clk_enable(vpu_clk)

// In gx_i2c_xfer(), add recovery if (status & I2C_STAT_BUS_BUSY) gx_i2c_reset(adap); mdelay(1);