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

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Message-ID: <20180409153631.GB19682@codeaurora.org>
Date:   Mon, 9 Apr 2018 09:36:31 -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 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.

Thanks,
Lina