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Subject: Re: [PATCH v3,5/5] powerpc: sysdev: support userspace access of
 fsl_85xx_sram
To:     Wang Wenhu <wenhu.wang@vivo.com>, gregkh@linuxfoundation.org,
        arnd@arndb.de, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org
Cc:     oss@buserror.net, kernel@vivo.com, robh@kernel.org,
        benh@kernel.crashing.org, paulus@samba.org,
        Michael Ellerman <mpe@ellerman.id.au>
References: <20200424024554.30709-1-wenhu.wang@vivo.com>
 <20200424024554.30709-6-wenhu.wang@vivo.com>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <0dfd17ca-d11e-9cf3-177e-bce0b8eace5c@c-s.fr>
Date:   Fri, 24 Apr 2020 07:29:09 +0200
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Le 24/04/2020 à 04:45, Wang Wenhu a écrit :
> New module which registers its memory allocation and free APIs to the
> sram_dynamic module, which would create a device of struct sram_device
> type to act as an interface for user level applications to access the
> backend hardware device, fsl_85xx_cache_sram, which is drived by the
> FSL_85XX_CACHE_SRAM module.
> 
> Signed-off-by: Wang Wenhu <wenhu.wang@vivo.com>
> Cc: Christophe Leroy <christophe.leroy@c-s.fr>
> Cc: Scott Wood <oss@buserror.net>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: linuxppc-dev@lists.ozlabs.org
> ---
>   .../powerpc/include/asm/fsl_85xx_cache_sram.h |  4 ++
>   arch/powerpc/platforms/85xx/Kconfig           | 10 +++++
>   arch/powerpc/sysdev/Makefile                  |  1 +
>   arch/powerpc/sysdev/fsl_85xx_cache_ctlr.h     |  6 +++
>   arch/powerpc/sysdev/fsl_85xx_cache_sram.c     | 12 ++++++
>   arch/powerpc/sysdev/fsl_85xx_sram_uapi.c      | 39 +++++++++++++++++++
>   6 files changed, 72 insertions(+)
>   create mode 100644 arch/powerpc/sysdev/fsl_85xx_sram_uapi.c

We shouldn't add more stuff in arch/powerpc/sysdev/

Either it is dedicated to 85xx, and it should go into 
arch/powerpc/platform/85xx/ , or it is common to several 
platforms/architectures and should be moved to drivers/soc/fsl/

> 
> diff --git a/arch/powerpc/include/asm/fsl_85xx_cache_sram.h b/arch/powerpc/include/asm/fsl_85xx_cache_sram.h
> index 0235a0447baa..99cb7e202c38 100644
> --- a/arch/powerpc/include/asm/fsl_85xx_cache_sram.h
> +++ b/arch/powerpc/include/asm/fsl_85xx_cache_sram.h
> @@ -26,6 +26,10 @@ struct mpc85xx_cache_sram {
>   	unsigned int size;
>   	rh_info_t *rh;
>   	spinlock_t lock;
> +
> +#ifdef CONFIG_FSL_85XX_SRAM_UAPI
> +	struct device *dev;
> +#endif
>   };
>   
>   extern void mpc85xx_cache_sram_free(void *ptr);
> diff --git a/arch/powerpc/platforms/85xx/Kconfig b/arch/powerpc/platforms/85xx/Kconfig
> index fa3d29dcb57e..3a6f6af973eb 100644
> --- a/arch/powerpc/platforms/85xx/Kconfig
> +++ b/arch/powerpc/platforms/85xx/Kconfig
> @@ -16,6 +16,16 @@ if FSL_SOC_BOOKE
>   
>   if PPC32
>   
> +config FSL_85XX_SRAM_UAPI
> +	tristate "Freescale MPC85xx SRAM UAPI Support"
> +	depends on FSL_SOC_BOOKE && SRAM_DYNAMIC

Is SRAM_DYNAMIC usefull on its own, without a driver like this one ? Is 
that worth allowing tiny selection of both drivers ? Shouldn't one of 
them imply the other one ?

> +	select FSL_85XX_CACHE_SRAM
> +	help
> +	  This registers a device of struct sram_device type which would act as
> +	  an interface for user level applications to access the Freescale 85xx
> +	  Cache-SRAM memory dynamically, meaning allocate on demand dynamically
> +	  while they are running.
> +
>   config FSL_85XX_CACHE_SRAM
>   	bool
>   	select PPC_LIB_RHEAP
> diff --git a/arch/powerpc/sysdev/Makefile b/arch/powerpc/sysdev/Makefile
> index cb5a5bd2cef5..e71f82f0d2c3 100644
> --- a/arch/powerpc/sysdev/Makefile
> +++ b/arch/powerpc/sysdev/Makefile
> @@ -24,6 +24,7 @@ obj-$(CONFIG_FSL_CORENET_RCPM)	+= fsl_rcpm.o
>   obj-$(CONFIG_FSL_LBC)		+= fsl_lbc.o
>   obj-$(CONFIG_FSL_GTM)		+= fsl_gtm.o
>   obj-$(CONFIG_FSL_85XX_CACHE_SRAM)	+= fsl_85xx_l2ctlr.o fsl_85xx_cache_sram.o
> +obj-$(CONFIG_FSL_85XX_SRAM_UAPI)	+= fsl_85xx_sram_uapi.o
>   obj-$(CONFIG_FSL_RIO)		+= fsl_rio.o fsl_rmu.o
>   obj-$(CONFIG_TSI108_BRIDGE)	+= tsi108_pci.o tsi108_dev.o
>   obj-$(CONFIG_RTC_DRV_CMOS)	+= rtc_cmos_setup.o
> diff --git a/arch/powerpc/sysdev/fsl_85xx_cache_ctlr.h b/arch/powerpc/sysdev/fsl_85xx_cache_ctlr.h
> index ce370749add9..4930784d9852 100644
> --- a/arch/powerpc/sysdev/fsl_85xx_cache_ctlr.h
> +++ b/arch/powerpc/sysdev/fsl_85xx_cache_ctlr.h
> @@ -10,6 +10,8 @@
>   #ifndef __FSL_85XX_CACHE_CTLR_H__
>   #define __FSL_85XX_CACHE_CTLR_H__
>   
> +#include <linux/platform_device.h>
> +
>   #define L2CR_L2FI		0x40000000	/* L2 flash invalidate */
>   #define L2CR_L2IO		0x00200000	/* L2 instruction only */
>   #define L2CR_SRAM_ZERO		0x00000000	/* L2SRAM zero size */
> @@ -81,6 +83,10 @@ struct sram_parameters {
>   	phys_addr_t sram_offset;
>   };
>   
> +#ifdef CONFIG_FSL_85XX_SRAM_UAPI
> +extern struct mpc85xx_cache_sram *mpc85xx_get_cache_sram(void);

'extern' keywork is meaningless here, remove it.

> +#endif
> +
>   extern int instantiate_cache_sram(struct platform_device *dev,
>   		struct sram_parameters sram_params);
>   extern void remove_cache_sram(struct platform_device *dev);
> diff --git a/arch/powerpc/sysdev/fsl_85xx_cache_sram.c b/arch/powerpc/sysdev/fsl_85xx_cache_sram.c
> index 3de5ac8382c0..0156ea63a3a2 100644
> --- a/arch/powerpc/sysdev/fsl_85xx_cache_sram.c
> +++ b/arch/powerpc/sysdev/fsl_85xx_cache_sram.c
> @@ -23,6 +23,14 @@
>   
>   struct mpc85xx_cache_sram *cache_sram;
>   
> +
> +#ifdef CONFIG_FSL_85XX_SRAM_UAPI
> +struct mpc85xx_cache_sram *mpc85xx_get_cache_sram(void)
> +{
> +	return cache_sram;
> +}
> +#endif

This function is not worth the mess of an #ifdef in a .c file.
cache_sram is already globaly visible, so this function should go in 
fsl_85xx_cache_ctlr.h as a 'static inline'

> +
>   void *mpc85xx_cache_sram_alloc(unsigned int size,
>   				phys_addr_t *phys, unsigned int align)
>   {
> @@ -115,6 +123,10 @@ int instantiate_cache_sram(struct platform_device *dev,
>   	rh_attach_region(cache_sram->rh, 0, cache_sram->size);
>   	spin_lock_init(&cache_sram->lock);
>   
> +#ifdef CONFIG_FSL_85XX_SRAM_UAPI
> +	cache_sram->dev = &dev->dev;
> +#endif

	Can we avoid the #ifdef in .c file ? (see 
https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation)

> +
>   	dev_info(&dev->dev, "[base:0x%llx, size:0x%x] configured and loaded\n",
>   		(unsigned long long)cache_sram->base_phys, cache_sram->size);
>   
> diff --git a/arch/powerpc/sysdev/fsl_85xx_sram_uapi.c b/arch/powerpc/sysdev/fsl_85xx_sram_uapi.c
> new file mode 100644
> index 000000000000..60190bf3c8e9
> --- /dev/null
> +++ b/arch/powerpc/sysdev/fsl_85xx_sram_uapi.c
> @@ -0,0 +1,39 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) 2020 Vivo Communication Technology Co. Ltd.
> + * Copyright (C) 2020 Wang Wenhu <wenhu.wang@vivo.com>
> + * All rights reserved.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/sram_dynamic.h>
> +#include <asm/fsl_85xx_cache_sram.h>
> +#include "fsl_85xx_cache_ctlr.h"
> +
> +static struct sram_api mpc85xx_sram_api = {
> +	.name = "mpc85xx_sram",
> +	.alloc = mpc85xx_cache_sram_alloc,
> +	.free = mpc85xx_cache_sram_free,
> +};
> +
> +static int __init mpc85xx_sram_uapi_init(void)
> +{
> +	struct mpc85xx_cache_sram *sram = mpc85xx_get_cache_sram();
> +
> +	if (!sram)
> +		return -ENODEV;
> +
> +	return sram_register_device(sram->dev, &mpc85xx_sram_api);
> +}
> +subsys_initcall(mpc85xx_sram_uapi_init);
> +
> +static void __exit mpc85xx_sram_uapi_exit(void)
> +{
> +	sram_unregister_device(&mpc85xx_sram_api);
> +}
> +module_exit(mpc85xx_sram_uapi_exit);
> +
> +MODULE_AUTHOR("Wang Wenhu <wenhu.wang@vivo.com>");
> +MODULE_DESCRIPTION("MPC85xx SRAM User-Space API Support");
> +MODULE_LICENSE("GPL v2");
> 

Christophe