Hi Kever,
On 3/8/24 11:05, Kever Yang wrote:
Hi Quentin,
On 2024/2/21 18:37, Quentin Schulz wrote:
From: Quentin Schulzquentin.schulz@theobroma-systems.com
Rockchip SoCs have some jtag/sdmmc autoswitching that simply doesn't work really well.[00] The Linux kernel disables it for all SoCs[01], so U-Boot needs to do the same in order to fix issues related to SD card on RK3588. This autoswitching is enabled (by default) via the force_jtag bitfield in SYS_GRF_SOC_CON6 in the TRM part1.
The conditions to enter forced JTAG mode are the following:
- force_jtag is 1
- GPIO4_D2 is muxed for SDMMC function
- GPIO3_D3 is muxed for SDMMC function
- SDMMC_DET is inactive
I have explain the reason and send fix for other boards in kernel for why the force jtag
function not working correctly, see patch [1] and I copy the commit message here:
RK3588 has force_jtage feature which is enable JTAG function via sdmmc pins automatically when there is no SD card insert, this feature will need the GPIO0A4 works in sdmmc_det function like other mmc signal instead of GPIO function, or else the force_jtag can not auto be disabled when SD card insert.
For the rk3588 boards available on mainline kernel, 10 boards enable SD card function and 9 of then use GPIO0A4 as sdmmc_det, they should all able to use the force_jtag after my patch apply. The jaguar-rk3588 still have the issue because there is no sdmmc_det used. The condition of force JTAG mode work correctly is :
- force_jtag in grf is 1;
- all the SDMMC signal including SDMMC_DET set as SDMMC function in GRF
IOC/IOMUX reg;
So please update the commit message and it would be better to move this setting in jaguar-rk3588 board
Thanks, it's a tiny bit clearer to me now. We never exit this JTAG mode on Jaguar because we have GPIO0A4 floating (with internal pull-down). On Tiger (patches coming this month I hope), it's hardwired to ground but we use a different GPIO as card detect, so we'll have a similar issue. In any case, thanks for the explanation.
Though, I do not understand why you absolutely want this force_jtag to be always enabled. It is a debug feature.
Even more so, this is a security issue. I don't think anyone wants to have the JTAG enabled if the user plays with the card detect pin or boot without an SD card connected. I really insist this should be enabled on the SoC level, the same way that the Linux kernel does it.
We could compromise on a Kconfig symbol to enable force_jtag for people who want it but still default to disabled on the SoC level, but I'm not really seeing a reason for it.
so that other board can enable force_jtag with only modify kernel but not both kernel and U-Boot.
If you want JTAG support in U-Boot, you would patch U-Boot. If you want JTAG support in the kernel, you would patch the kernel. If you want it in both, you'd patch both. I'm not sure to understand what disabling force_jtag in U-Boot has to do with force_jtag enabled from the Linux kernel, what am I missing here?
Cheers, Quentin