linux-kernel - RE: [PATCH v2 2/3] firmware: Keem Bay: Add support for Arm Trusted Firmware Service call

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Date:   Sat, 3 Oct 2020 19:03:13 +0000
From:   "Zulkifli, Muhammad Husaini" <muhammad.husaini.zulkifli@...el.com>
To:     Sudeep Holla <sudeep.holla@....com>,
        Michal Simek <michal.simek@...inx.com>
CC:     "Hunter, Adrian" <adrian.hunter@...el.com>,
        "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Raja Subramanian, Lakshmi Bai" 
        <lakshmi.bai.raja.subramanian@...el.com>,
        "arnd@...db.de" <arnd@...db.de>,
        "Wan Mohamad, Wan Ahmad Zainie" 
        <wan.ahmad.zainie.wan.mohamad@...el.com>
Subject: RE: [PATCH v2 2/3] firmware: Keem Bay: Add support for Arm Trusted
 Firmware Service call

Hi Sudeep,

>-----Original Message-----
>From: Sudeep Holla <sudeep.holla@....com>
>Sent: Friday, October 2, 2020 10:51 PM
>To: Michal Simek <michal.simek@...inx.com>
>Cc: Zulkifli, Muhammad Husaini <muhammad.husaini.zulkifli@...el.com>;
>Hunter, Adrian <adrian.hunter@...el.com>; ulf.hansson@...aro.org; linux-
>mmc@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
>kernel@...r.kernel.org; Raja Subramanian, Lakshmi Bai
><lakshmi.bai.raja.subramanian@...el.com>; arnd@...db.de; Sudeep Holla
><sudeep.holla@....com>; Wan Mohamad, Wan Ahmad Zainie
><wan.ahmad.zainie.wan.mohamad@...el.com>
>Subject: Re: [PATCH v2 2/3] firmware: Keem Bay: Add support for Arm Trusted
>Firmware Service call
>
>Hi Michal,
>
>On Fri, Oct 02, 2020 at 03:53:33PM +0200, Michal Simek wrote:
>> Hi Sudeep,
>>
>> On 02. 10. 20 12:58, Sudeep Holla wrote:
>> > Hi Michal,
>> >
>> > On Fri, Oct 02, 2020 at 10:23:02AM +0200, Michal Simek wrote:
>> >> Hi Sudeep,
>> >>
>> >> On 01. 10. 20 17:35, Sudeep Holla wrote:
>> >
>> > [...]
>> >
>> >>>
>> >>> What are the other uses of this KEEMBAY_SIP_* ?
>> >>> For now I tend to move this to the driver making use of it using
>> >>> arm_smccc_1_1_invoke directly if possible. I don't see the need
>> >>> for this to be separate driver. But do let us know the features
>> >>> implemented in the firmware. If it is not v1.1+, reasons for not
>> >>> upgrading as you need v1.1 for some CPU errata implementation.
>> >>
>> >> This driver has been created based on my request to move it out the
>> >> mmc driver. It looks quite hacky to have arm_smccc_res and call
>> >> arm_smccc_smc() also with some IDs where it is visible that the
>> >> part of ID is just based on any spec.
>> >
>> > OK, driver is fine but no dt-bindings as it is discoverable. It can
>> > also be just a wrapper library instead as it needs no explicit
>> > initialisation like drivers to setup.
>>
>> I am fine with it. Do we have any example which we can point him to?
>>
>
>You seem to have figured that out already with SOC_ID example.
>That was quick I must say 😄.
>
>>
>> >
>> >> Also in v1 he is just calling SMC. But maybe there is going a need
>> >> to call HVC instead which is something what device driver shouldn't
>> >> decide that's why IMHO doing step via firmware driver is much better
>approach.
I will add func for HVC also in case in the future if someone want to use it.
>> >
>> > Agreed and one must use arm_smccc_get_conduit or something similar.
>> > No additional bindings for each and ever platform and driver that
>> > uses SMCCC please.
>> >
>> >> Of course if there is a better/cleaner way how this should be done
>> >> I am happy to get more information about it.
>> >>
>> >
>> > Let me know what you think about my thoughts stated above.
>>
>>
>> I am fine with it. The key point is to have these sort it out because
>> I see that a lot of drivers just simply call that SMCs from drivers
>> which is IMHO wrong.
>>
>
>Sure, sorry I didn't express my concern properly. I want to avoid dt bindings for
>these and use the SMCCC discovery we have in place already if possible.
>
>If this driver had consumers in the DT and it needs to be represented in DT, it is
>a different story and I agree for need for a driver there.
>But I don't see one in this usecase.

Does it ok if I do some checking in arasan controller driver as below and 
represented it in the DT of arasan,sdhci.yaml:
This is to ensure that for Keem Bay SOC specific, Keembay_firmware node must be consume.

	if (of_device_is_compatible(np, "intel,keembay-sdhci-5.1-sd")) {
		struct device_node *dn;
		struct gpio_desc *uhs;

		dn = of_find_node_by_name(NULL, "keembay_firmware");
		if (!dn)
			return dev_err_probe(dev, PTR_ERR(dn),
						"can't find keembay_firmware node\n");
		of_node_put(dn);
..........
}

Thanks
>
>>
>> BTW: I see you have added soc id reading which you are saying is the
>> part of smcc v1.2 but I can't see any implementation in TF-A. Is this
>> spec publicly available?
>>
>
>Spec is out[1], include/linux/arm-smccc.h points to the latest spec.
>TF-A does have implementation as I tested with it and even reported bug that I
>discovered when I tested with my patches that are now merged upstream. Are
>you referring to master of TF-A or last release version ?
>If latter, it had bug and may not be working. I may be wrong though, as I am just
>telling what was told to me couple of months back and things might have
>changed in TF-A land.
>
>--
>Regards,
>Sudeep
>
>[1] https://developer.arm.com/documentation/den0028/latest