linux-kernel - Re: [PATCH] interconnect: qcom: fix rpmh link failures

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Date:   Fri, 4 Dec 2020 17:27:10 -0600
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Sibi Sankar <sibis@...eaurora.org>,
        Evan Green <evgreen@...omium.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Odelu Kukatla <okukatla@...eaurora.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        David Dai <daidavid1@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] interconnect: qcom: fix rpmh link failures

On Fri 04 Dec 10:50 CST 2020, Arnd Bergmann wrote:

> From: Arnd Bergmann <arnd@...db.de>
> 
> When CONFIG_COMPILE_TEST is set, it is possible to build some
> of the interconnect drivers into the kernel while their dependencies
> are loadable modules, which is bad:
> 
> arm-linux-gnueabi-ld: drivers/interconnect/qcom/bcm-voter.o: in function `qcom_icc_bcm_voter_commit':
> (.text+0x1f8): undefined reference to `rpmh_invalidate'
> arm-linux-gnueabi-ld: (.text+0x20c): undefined reference to `rpmh_write_batch'
> arm-linux-gnueabi-ld: (.text+0x2b0): undefined reference to `rpmh_write_batch'
> arm-linux-gnueabi-ld: (.text+0x2e8): undefined reference to `rpmh_write_batch'
> arm-linux-gnueabi-ld: drivers/interconnect/qcom/icc-rpmh.o: in function `qcom_icc_bcm_init':
> (.text+0x2ac): undefined reference to `cmd_db_read_addr'
> arm-linux-gnueabi-ld: (.text+0x2c8): undefined reference to `cmd_db_read_aux_data'
> 
> The exact dependencies are a bit complicated, so split them out into a
> hidden Kconfig symbol that all drivers can in turn depend on to get it
> right.
> 
> Fixes: 976daac4a1c5 ("interconnect: qcom: Consolidate interconnect RPMh support")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Your patch looks correct to me, so:
Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>


But we're going to have to sprinkle a handful of these throughout the
tree and we're not a lot of people who "understand" what it does (and at
least I keep getting them wrong...)

Perhaps it would be more reasonable to maintain this long term if we
drop the possibility of compile testing these drivers independently of
rpmh and command db? (I.e. drop the function stubs and rely on
RPMH/COMMAND_DB to enable building under COMPILE_TEST)?


And just to make it clear, I think we should merge your patch to fix
v5.11; then consider to simplify this past that.

Regards,
Bjorn

> ---
>  drivers/interconnect/qcom/Kconfig | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/interconnect/qcom/Kconfig b/drivers/interconnect/qcom/Kconfig
> index a8f93ba265f8..b3fb5b02bcf1 100644
> --- a/drivers/interconnect/qcom/Kconfig
> +++ b/drivers/interconnect/qcom/Kconfig
> @@ -42,13 +42,23 @@ config INTERCONNECT_QCOM_QCS404
>  	  This is a driver for the Qualcomm Network-on-Chip on qcs404-based
>  	  platforms.
>  
> +config INTERCONNECT_QCOM_RPMH_POSSIBLE
> +	tristate
> +	default INTERCONNECT_QCOM
> +	depends on QCOM_RPMH || (COMPILE_TEST && !QCOM_RPMH)
> +	depends on QCOM_COMMAND_DB || (COMPILE_TEST && !QCOM_COMMAND_DB)
> +	depends on OF || COMPILE_TEST
> +	help
> +	  Compile-testing RPMH drivers is possible on other platforms,
> +	  but in order to avoid link failures, drivers must not be built-in
> +	  when QCOM_RPMH or QCOM_COMMAND_DB are loadable modules
> +
>  config INTERCONNECT_QCOM_RPMH
>  	tristate
>  
>  config INTERCONNECT_QCOM_SC7180
>  	tristate "Qualcomm SC7180 interconnect driver"
> -	depends on INTERCONNECT_QCOM
> -	depends on (QCOM_RPMH && QCOM_COMMAND_DB && OF) || COMPILE_TEST
> +	depends on INTERCONNECT_QCOM_RPMH_POSSIBLE
>  	select INTERCONNECT_QCOM_RPMH
>  	select INTERCONNECT_QCOM_BCM_VOTER
>  	help
> @@ -57,8 +67,7 @@ config INTERCONNECT_QCOM_SC7180
>  
>  config INTERCONNECT_QCOM_SDM845
>  	tristate "Qualcomm SDM845 interconnect driver"
> -	depends on INTERCONNECT_QCOM
> -	depends on (QCOM_RPMH && QCOM_COMMAND_DB && OF) || COMPILE_TEST
> +	depends on INTERCONNECT_QCOM_RPMH_POSSIBLE
>  	select INTERCONNECT_QCOM_RPMH
>  	select INTERCONNECT_QCOM_BCM_VOTER
>  	help
> @@ -67,8 +76,7 @@ config INTERCONNECT_QCOM_SDM845
>  
>  config INTERCONNECT_QCOM_SM8150
>  	tristate "Qualcomm SM8150 interconnect driver"
> -	depends on INTERCONNECT_QCOM
> -	depends on (QCOM_RPMH && QCOM_COMMAND_DB && OF) || COMPILE_TEST
> +	depends on INTERCONNECT_QCOM_RPMH_POSSIBLE
>  	select INTERCONNECT_QCOM_RPMH
>  	select INTERCONNECT_QCOM_BCM_VOTER
>  	help
> @@ -77,8 +85,7 @@ config INTERCONNECT_QCOM_SM8150
>  
>  config INTERCONNECT_QCOM_SM8250
>  	tristate "Qualcomm SM8250 interconnect driver"
> -	depends on INTERCONNECT_QCOM
> -	depends on (QCOM_RPMH && QCOM_COMMAND_DB && OF) || COMPILE_TEST
> +	depends on INTERCONNECT_QCOM_RPMH_POSSIBLE
>  	select INTERCONNECT_QCOM_RPMH
>  	select INTERCONNECT_QCOM_BCM_VOTER
>  	help
> -- 
> 2.27.0
>