How to configure Clock Stop Control Register

[Henbin Chang]

The 'memory-region' is also the mandatory attribute for the loading of
lpc-ctrl driver.

node = of_parse_phandle(dev->of_node, "memory-region", 0);
    if (!node) {
        dev_err(dev, "Didn't find reserved memory\n");
        return -EINVAL;
    }

Could anyone share the explanation?

Thanks for your help.


2018-06-07 13:26 GMT+08:00 Henbin Chang <henbinchang at gmail.com>:

> Hi Joel,
>
> Thanks for your response.
>
> But I don't understand why 'SCU0C[8] = 1' is related with
> aspeed_lpc_ctrl_ioctl().
>
> I don't see any code to write SCU0C register In the
> aspeed_lpc_ctrl_ioctl().
>
> Update my finding.
>
> I find the aspeed-lpc-ctrl driver can throw the below error message and
> 'return -ENODEV',
> 'Didn't find host pnor flash node'
>
> After checking the my dts, it lacks of the 'flash' filed in the lpc_ctrl .
>
> So I refer the aspeed-bmc-opp-zaius.dts and add it into my dts.
> &lpc_ctrl {
>     status = "okay";
>     memory-region = <&flash_memory>;
>     flash = <&spi1>;
> };
>
> And then the lpc aspeed-lpc-ctrl driver can be loaded successfully.
> And the SCU0C[8] isn't set as 1b'.
>
> For my understanding, the 'spi1' indicates the system SPI connected into
> BIOS SPI flash.
> I don't know why lpc_ctrl has to need the 'flash' field.
>
> Thanks for your help.
>
> 2018-06-06 17:01 GMT+08:00 Joel Stanley <joel at jms.id.au>:
>
>> Hello Henbin,
>>
>> tldr: you need to ensure mboxd has run so the aspeed-lpc-ctrl ioctl
>> has been performed.
>>
>> See below for my explanation.
>>
>> On 6 June 2018 at 14:32, Henbin Chang <henbinchang at gmail.com> wrote:
>> >> What kernel tree are you building/booting? Can you provide a link?
>> >> Currently we've tied the LCLK to enabling LPC2AHB bridge:
>> >>
>> >> https://github.com/openbmc/linux/blob/dev-4.13/arch/arm/boot
>> /dts/aspeed-g5.dtsi#L302
>> >> You may need to add the following to your dts if you've developed your
>> >> own:
>> >> ```
>> >> &lpc_ctrl {
>> >>         status = "okay";
>> >> };
>> >
>> > I use dev-4.13 branch (the last commit is
>> > aca92be80c008bceeb6fb62fd1d450b5be5d0a4f).
>> >
>> > The aspeed-g5.dtsi I use is the same with the one in your link.
>> >
>> > I follow your suggestion and add the following to my dts but the
>> SCU0C[8] is
>> > still 1b'.
>> >
>> > &lpc_ctrl {
>> >         status = "okay";
>> > };
>> >
>> > Even I directly change the status of lpc_ctrl to 'okay'  in the
>> > aspeed-g5.dtsi,  the SCU0C[8] is still 1b'.
>> > lpc_ctrl: lpc-ctrl at 0 {
>> >      compatible = "aspeed,ast2500-lpc-ctrl";
>> >      reg = <0x0 0x80>;
>> >      clocks = <&syscon ASPEED_CLK_GATE_LCLK>;
>> >      status = "okay";
>> >  };
>>
>> Doing these two are equivalent. But it never hurts to try when things
>> aren't working :)
>>
>> >
>> > devmem 0x1e6e200c 32
>> > 0xFFCDBF8B
>>
>> If you take a look a the driver, you will see this snippet:
>>
>> drivers/misc/aspeed-lpc-ctrl.c
>>
>> static long aspeed_lpc_ctrl_ioctl(struct file *file, unsigned int cmd,
>>                 unsigned long param)
>> {
>>                 /*
>>                  * Enable LPC FHW cycles. This is required for the host to
>>                  * access the regions specified.
>>                  */
>>                 return regmap_update_bits(lpc_ctrl->regmap, HICR5,
>>                                 HICR5_ENFWH | HICR5_ENL2H,
>>                                 HICR5_ENFWH | HICR5_ENL2H);
>>
>>
>> The driver is designed to only enable the bridge (ENL2H) when the
>> configuration registers have been programmed by an ioctl() from
>> userspace.
>>
>> This is to ensure the window is pointing at an area of memory that has
>> been chosen by the system integrator, and not accidentally exposing
>> some BMC RAM to the host. So the ioctl for programming the window will
>> automatically enable the FWH and L2H bits (bits 10 and 8).
>>
>> On OpenPower systems, the tool that performs the ioctl is 'mboxd'. If
>> you are using an OpenPower system, where the host firmware talks the
>> mbox protocol (hostboot and skiboot do this), then you should run
>> mboxd.
>>
>> If you're running on another platform, you could write a small utility
>> to do this ioctl from userspace. I wrote one in Rust a few months ago,
>> but you probably want to use C instead.
>>
>> Cheers,
>>
>> Joel
>>
>
>
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