Hi Alex,
From: Alex G. mr.nuke.me@gmail.com Sent: jeudi 10 septembre 2020 22:10
On 9/10/20 11:04 AM, Patrick DELAUNAY wrote:
Hi Alexandru,
Hi
[snip]
- cfg->f_max = 52000000;
- mmc_of_parse(dev, cfg);
Result of mmc_of_parse is not tested ?
I proposed:
- ret = mmc_of_parse(dev, cfg);
- if (ret)
return ret;You're right. I'll get that updated.
Thanks;
I test this patch with a trace in stm32_sdmmc2_probe on STM32MP157C-EV1
[snip]
I think that it is a issue U-Boot, in mmc uclass in mmc_of_parse():
if (dev_read_bool(dev, "cap-mmc-highspeed"))
cfg->host_caps |= MMC_CAP(MMC_HS);
cfg->host_caps |= MMC_CAP(MMC_HS) |MMC_CAP(MMC_HS_52);
In U-Boot this capability is splitted in 2 bits = one for 26MHz one for 52MHz And for card side it is managed on card side by mmc_get_capabilities()
I agree. I am preparing a patch to address this.
Thanks;
[snip]
- some host caps can be added in device tree (they are supported by SOC and
by Linux driver)
but they are not supported by U-Boot driver, for example:#define MMC_MODE_DDR_52MHz MMC_CAP(MMC_DDR_52) #define MMC_MODE_HS200 MMC_CAP(MMC_HS_200) #define MMC_MODE_HS400 MMC_CAP(MMC_HS_400) #define MMC_MODE_HS400_ES MMC_CAP(MMC_HS_400_ES)
I afraid (I don't sure) that this added caps change the mmc core behavior in U-Boot = U-Boot try to select the high speed mode even if not
supported by driver....
Two issues here. The first is when devicetree enables an unsupported mode, say "mmc-hs400-1_2v". That's a devicetree bug, and not something we should fix in the code. Hypothetical exam: DT says bus-width = <8>; but only four lines are routed on the board.
Yes it is a device tree issue when the mode is not supported by board / SOC.
But high mode is supported by the STM32MP15x SOC but only if additional Operation are done (IO configuration to support higher speed)
It is not supported in U-Boot driver (yet ?) but it is supported by Linux driver...
The second issue is what happens when somebody plugs in a UHS SD card? UHS support is not enabled by default in the stm32mp1 defconfigs, so the mmc core won't try to run it at UHS.
Now if somebody were to enable UHS manually: CONFIG_MMC_IO_VOLTAGE=y CONFIG_MMC_UHS_SUPPORT=y Then yes, the UHS switch will be attempted, fail, and the card will not be detected.
To work around that, one could implement a .wait_dat0() that returns an error other than -ENOSYS. This would cause mmc_switch_voltage() to fail, making the mmc core to leave the card at default speeds.
My argument is that it takes conscious effort to break things in the first place, so it's not a situation we should worry about.
Yes we should have issue only if UHS defconfig was activated (CONFIG_MMC_UHS_SUPPORT, CONFIG_MMC_HS*_SUPPORT)....
And it is not the case today in stm32*defconfig And my proposal is protection (over).
The host_caps bitfield should be limited by the supported features in the driver
(or remove the unsupported features) [snip]
cfg->host_caps &= SDMMC_SUPPORTED_CAPS; or cfg->host_caps |= ~SDMMC_UNSUPPORTED_CAPS;
I think this sort of playing with the flags will cause more confusion. People would expect this to come from DT. For example, somebody sets "sd-uhs-ddr52" in devicetree. It's more confusing to check host_caps, and find that MMC_MODE_DDR_52MHz is not set than it is to see the driver trying to place the card in DDR52 and failing.
- card_caps = CARD capacity
For you - host_caps is SOC capacity (read from DT)
For me - host_caps is SOC capacity (read from DT) AND driver capacity
=> then in mmc u-class, the real capacity is host_caps | card_caps
I already see this kind of limitation in one driver omap_hsmmc.c:1939: cfg->host_caps &= ~fixups->unsupported_caps;
But I agree it is today an over protection on host_caps and it can be confusing so you can forget this point....
Alex
Regards
Patrick