[REGRESSION] mmc: "unable to select a mode: -5" on i.MX8M/AM62 platforms

[Peng Fan]

Hi Vitor,

> Subject: [REGRESSION] mmc: "unable to select a mode: -5" on
> i.MX8M/AM62 platforms
> 
> Hi,
> 
> U-Boot 2026.01 fails to initialize MMC devices on multiple platforms
> with "unable to select a mode: -5" during mmc_select_mode().
> 
> Affected platforms:
> - Verdin iMX8M Mini (SPL boot failure - cannot boot at all)
> - Verdin iMX8M Plus (MMC init fails in U-Boot proper - cannot boot)
> - SMARC iMX8M Plus (MMC init fails in U-Boot proper)
> - Verdin AM62 (boot failure, no output)
> 
> All platforms use eMMC and worked correctly prior to this regression.
> 
> Bisect results:
> - Last known good commit: 228810d0bac3
> - Known bad commit: 36aeeb591b0d
> 
> Between these commits, several MMC-related changes were merged.
> These seem particularly relevant:
> commit aebb523a2381 ("mmc: mmc-uclass: Use max-frequency from
> device tree with default handling") commit 1e40e419aeb2 ("mmc:
> sdhci-cadence: Use max-frequency property from device
> tree")
> commit fa7e82127fad ("mmc: sdhci-cadence: Set controller and PHY
> speed modes for SD and eMMC cards")

Thanks for the report. I meet same issue on i.MX93, checking..

Thanks,
Peng.

> 
> Could someone familiar with these recent changes help identify what
> might have changed in the mode selection logic?
> 
> === Example logs ===
> 
> Verdin iMX8M Mini (SPL failure):
> 
> U-Boot SPL 2026.01-0.0.0-devel+git.53c0d5b38795 (Jan 06 2026 -
> 20:44:27 +0000)
> WDT:   Started watchdog at 30280000 with servicing every 1000ms
> (60s timeout)
> SEC0:  RNG instantiated
> Trying to boot from MMC1
> unable to select a mode: -5
> spl: mmc init failed with error: -524
> Error: -524
> SPL: Unsupported Boot Device!
> SPL: failed to boot from all boot devices ### ERROR ### Please RESET
> the board ###
> 
> ---
> 
> Verdin iMX8M Plus (U-Boot proper failure):
> 
> U-Boot SPL 2026.01-0.0.0-devel+git.53c0d5b38795 (Jan 06 2026 -
> 20:44:27 +0000) DDR configured as dual rank
> WDT:   Started watchdog at 30280000 with servicing every 1000ms
> (60s timeout)
> SEC0:  RNG instantiated
> Normal Boot
> Trying to boot from BOOTROM
> Boot Stage: Primary boot
> Find img info 0x?, size 1208151552
> Need continue download 1024
> load_simple_fit: Skip load 'tee': image size is 0!
> NOTICE:  Do not release JR0 to NS as it can be used by HAB
> NOTICE:  BL31: v2.12.0(release):lf-6.12.20-2.0.0-dirty
> NOTICE:  BL31: Built : 08:15:07, May  9 2025
> 
> U-Boot 2026.01-0.0.0-devel+git.53c0d5b38795 (Jan 06 2026 -
> 20:44:27 +0000)
> 
> CPU:   NXP i.MX8MP[8] Rev1.1 A53 at 1200 MHz
> CPU:   Industrial temperature grade (-40C to 105C) at 23C
> DRAM:  8 GiB
> Core:  309 devices, 31 uclasses, devicetree: separate
> WDT:   Started watchdog at 30280000 with servicing every 1000ms
> (60s timeout)
> MMC:   FSL_SDHC: 1, FSL_SDHC: 2
> Loading Environment from MMC... unable to select a mode: -5
> 
> Verdin iMX8MP # saveenv
> Saving Environment to MMC... unable to select a mode: -5 No block
> device Failed (1)
> 
> ---
> 
> SMARC iMX8M Plus:
> 
> U-Boot SPL 2026.01-0.0.0-devel+git.53c0d5b38795 (Jan 06 2026 -
> 20:44:27 +0000) Training FAILED DDR configured as single rank
> SEC0:  RNG instantiated
> Normal Boot
> Trying to boot from BOOTROM
> Boot Stage: Primary boot
> Find img info 0x?, size 1208152064
> Need continue download 1024
> load_simple_fit: Skip load 'tee': image size is 0!
> NOTICE:  Do not release JR0 to NS as it can be used by HAB
> NOTICE:  BL31: v2.12.0(release):lf-6.12.20-2.0.0-dirty
> NOTICE:  BL31: Built : 08:15:07, May  9 2025
> 
> U-Boot 2026.01-0.0.0-devel+git.53c0d5b38795 (Jan 06 2026 -
> 20:44:27 +0000)
> 
> CPU:   NXP i.MX8MP[8] Rev1.1 A53 at 1200 MHz
> CPU:   Industrial temperature grade (-40C to 105C) at 23C
> DRAM:  4 GiB
> Core:  317 devices, 32 uclasses, devicetree: separate
> WDT:   Started watchdog at 30280000 with servicing every 1000ms
> (60s timeout)
> MMC:   FSL_SDHC: 1, FSL_SDHC: 0
> Loading Environment from MMC... unable to select a mode: -5
> *** Warning - No block device, using default environment unable to
> select a mode: -5 MMC init failed
> ---
> 
> I'm available to test patches or provide additional debug output if
> needed.
> 
> Best regards,
> Vitor Soares