linux-kernel - Re: [PATCH v5 04/10] drivers: qcom: rpmh: add RPMH helper functions

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Message-ID: <20180411163440.GF19682@codeaurora.org>
Date:   Wed, 11 Apr 2018 10:34:40 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     andy.gross@...aro.org, david.brown@...aro.org,
        linux-arm-msm@...r.kernel.org, linux-soc@...r.kernel.org,
        rnayak@...eaurora.org, bjorn.andersson@...aro.org,
        linux-kernel@...r.kernel.org, evgreen@...omium.org,
        dianders@...omium.org
Subject: Re: [PATCH v5 04/10] drivers: qcom: rpmh: add RPMH helper functions

On Tue, Apr 10 2018 at 20:23 -0600, Stephen Boyd wrote:
>Quoting Lina Iyer (2018-04-09 08:36:31)
>> On Fri, Apr 06 2018 at 19:21 -0600, Stephen Boyd wrote:
>> >Quoting Lina Iyer (2018-04-05 09:18:28)
>> >> diff --git a/include/soc/qcom/rpmh.h b/include/soc/qcom/rpmh.h
>> >> new file mode 100644
>> >> index 000000000000..95334d4c1ede
>> >> --- /dev/null
>> >> +++ b/include/soc/qcom/rpmh.h
>> >> @@ -0,0 +1,34 @@
>> >> +/* SPDX-License-Identifier: GPL-2.0 */
>> >> +/*
>> >> + * Copyright (c) 2016-2018, The Linux Foundation. All rights reserved.
>> >> + */
>> >> +
>> >> +#ifndef __SOC_QCOM_RPMH_H__
>> >> +#define __SOC_QCOM_RPMH_H__
>> >> +
>> >> +#include <soc/qcom/tcs.h>
>> >> +#include <linux/platform_device.h>
>> >> +
>> >> +struct rpmh_client;
>> >> +
>> >> +#if IS_ENABLED(CONFIG_QCOM_RPMH)
>> >> +int rpmh_write(struct rpmh_client *rc, enum rpmh_state state,
>> >> +              const struct tcs_cmd *cmd, u32 n);
>> >> +
>> >> +struct rpmh_client *rpmh_get_client(struct platform_device *pdev);
>> >> +
>> >> +void rpmh_release(struct rpmh_client *rc);
>> >
>> >Please get rid of this 'client' layer and fold it into the rpmh driver.
>> >Everything that uses the rpmh_client is a child device of the rpmh
>> >device so they should be able to just pass in their device pointer as
>> >their 'handle' and have the rpmh driver take that, get the parent device
>> >pointer, and pull an rpmh_drv structure out of there. The 'common' code
>> >can go into the base rpmh driver and get used from there and then we
>> >don't have to hop between two files to see how rpmh is used by the
>> >consumers. Code complexity goes down this way.
>>
>> That would be not be a good idea. This layer is not just providing an
>> API interface. There is resource buffering, handling of memory for
>> requests and downstream quirks and debug going on in this layer. It
>> would be unwise to clobber the hardware centric rpmh-rsc layer. If you
>> look at the series as a whole, you would understand why this is
>> necessary. I plan to build more on top of these patches in the future as
>> we add support for system low power modes. The complexity doesn't go
>> away, it just thrown in to another file, which is already decently
>> sized.
>>
>> I could try to use the device as a handle, and internally work on
>> getting the drv and other information from it, if that helps. But I do
>> not want to clobber these two files together. It doesn't help
>> maintainability.
>
>Using the device as a handle is a good start. Let's see how it looks
>once that part of the code gets replaced. I still fail to see how buffer
>management and requests are any different from poking the hardware, but
>OK. Maybe if this was a TCS "library" on top of the rpmh hardware
>interface?
This is essentially a TCS library.

-- Lina