On Thu, 25 Feb 2021 at 10:53, Nicolas Saenz Julienne
wrote:
>
> I'm seeing a rather odd behavior from sdhci-iproc's integration in BCM2711
> (Raspberry Pi 4's SoC), and would appreciate some opinions.
>
> The controller will timeout on SDHCI CMDs under the following conditions:
>
> - No SD card plugged in (the card polling thread is running, CD irq
> disabled).
> - BCM2711's VPU clock[1] configured at 500MHz or more, lower clocks are OK.
>
> There is no specific command that will time out, it seems random.
>
> Here's what I found out. The SDHCI controller runs at 100MHz, by bumping the
> frequency to 150MHz the issue disapears. Might be pure luck, or maybe I hit
> the
> nail and it's proper interference. Can't say.
As you probably know, I don't have the in-depth knowledge about this
HW. Although, let me provide a very vague guess. Could be that the
controller needs a higher clock rate to stay within some spec, for an
OPP/voltage domain for example?
In any case, assuming you get some confirmation from the Broadcom
folkz that this makes sense, you need to update the DT doc bindings
to add the clock-frequency property. In regards to this, please take
the opportunity to convert from legacy DT doc format
(brcm,sdhci-iproc.txt) into the new yaml format.
Kind regards
Uffe
>
> Regards,
> Nicolas
>
> ---
>
> [1] For those who are not aware, here's the relationship between VPU's clock
> and emmc2's:
>
> osc5400
> plld 300091
>plld_per75023
> emmc2149882908
> pllc 299988
>pllc_core0 6
> vpu 49998
>
> Nicolas Saenz Julienne (2):
> ARM: dts: Fix-up EMMC2 controller's frequency
> mmc: sdhci-iproc: Set clock frequency as per DT
>
> arch/arm/boot/dts/bcm2711-rpi-4-b.dts | 6 ++
> drivers/mmc/host/sdhci-iproc.c| 10 ++
> 2 files changed, 16 insertions(+)
>
> --
> 2.30.1
>
