SDIODriver 0.20

With today’s, 24Mar24, beta Pi ROM on a Raspberry Pi400 and RPi4 SDIOSlots shows what may be an unexpected frequency result. On the other hand it could be entirely correct.

The SDcard is a Sandisk Extreme.

*fx0
RISC OS 5.29 (21 Mar 2024)
*help SDIODriver
Module is: SDIODriver      0.19 (09 Mar 2024)

*SDIODevices
Bus Slt  RCA Fun  Description        Capacity     Vendor    Product Rev Date
  0   0  AAAA  0  SDHC card            30 Gbytes  SanDisk   SM32G   8.0 2021-01
  1   0  0001  1  SDIO non-standard function      Broadcom  A9A6
  1   0  0001  2  SDIO non-standard function      Broadcom  A9A6
  1   0  0001  3  SDIO Bluetooth Type-A           Broadcom  A9A6
*SDIOSlots
Bus Slt  Voltage  Width  Frequency
  0   0   3.3 V   4-bit   50 MHz SDR
  1   0   3.3 V   4-bit  500 kHz SDR
*

*FX0
RISC OS 5.29 (24 Mar 2024)
*
*help sdiodriver
==> Help on keyword SDIODriver
Module is: SDIODriver      0.20 (23 Mar 2024)

*sdiodevices
Bus Slt  RCA Fun  Description        Capacity     Vendor    Product Rev Date
  0   0  AAAA  0  SDHC card            30 Gbytes  SanDisk   SM32G   8.0 2021-01
  1   0  0001  1  SDIO non-standard function      Broadcom  A9A6
  1   0  0001  2  SDIO non-standard function      Broadcom  A9A6
  1   0  0001  3  SDIO Bluetooth Type-A           Broadcom  A9A6
*sdioslots
Bus Slt  Voltage  Width  Frequency
  0   0   3.3 V   4-bit   50 MHz SDR
  1   0   3.3 V   4-bit   41 MHz SDR
 *
 

Firmware :-

bootcode.bin  17Oct23
fixup.dat     20Mar24
fixup4.dat    20Mar24
start.elf     20Mar24
start4.elf    20Mar24

https://gitlab.riscosopen.org/RiscOS/Sources/HWSupport/SD/SDIODriver/commit/cd4a1229717c27abc86e3d0e103ca08d02c465a2

With today’s, 24Mar24, beta Pi ROM on a Raspberry Pi400 and RPi4 SDIOSlots shows what may be an unexpected frequency result. On the other hand it could be entirely correct.

Looks entirely correct to me. During testing of WiFi the 8200% speedup in access of the chip was deemed “worthwhile” by Ben.

The reason for the 41 is that the clock divisors are rather coarse so that’s as close as you can get and still be <= 50MHz. I believe you can hit exactly 50 on the Pi 3B+. I think if you got a scope on it you’d find that the SanDisk SM32G is also running at 41MHz and it’s just that *SDIOSlots is telling you the declared speed (for SD cards) versus the achieved speed (for IO cards).

You could have a go at twiddling the config.txt values to get a peripheral clock which can be divided exactly. We can’t be that far off reporting a more meaningful 42 figure.

Looks entirely correct to me.

Thanks for the explanation.

8200%

That is quite a big change in the reported speed.

worthwhile

Definitely.

I had got this far :-

djp@arcanite:~ $ sudo cat /sys/kernel/debug/mmc1/ios
clock:		50000000 Hz
actual clock:	41666667 Hz