Subject: Re: [PATCH 1/5] [v2][POWERPC] refactor dcr code

From: Benjamin Herrenschmidt <[email-masked]>
Date: Mon, 31 Mar 2008 09:02:56 +1100

On Fri, 2008-03-28 at 09:23 -0700, Stephen Neuendorffer wrote:
> Previously, dcr support was configured at compile time to either using
> MMIO or native dcr instructions.  Although this works for most
> platforms, it fails on FPGA platforms:
> 
> 1) Systems may include more than one dcr bus.
> 2) Systems may be native dcr capable and still use memory mapped dcr interface.
> 
> This patch provides runtime support based on the device trees for the
> case where CONFIG_PPC_DCR_MMIO and CONFIG_PPC_DCR_NATIVE are both
> selected.  Previously, this was a poorly defined configuration, which
> happened to provide NATIVE support.  The runtime selection is made
> based on the dcr slave device having a 'dcr-access-method' attribute
> in the device tree.  If only one of the above options is selected,
> then the code uses #defines to select only the used code in order to
> avoid interoducing overhead in existing usage.
> 
> Signed-off-by: Stephen Neuendorffer <[email-masked]>

Looks good. Haven't had a chance to test it yet, but tentatively

Acked-by: Benjamin Herrenschmidt <[email-masked]>

Initially, I thought about using function pointers but the if/else will
probably end up being more efficient. The only thing maybe to ponder
is whether we could avoid the dcr-generic.h file completely, and have
the generic wrappers be inline, though considering how slow DCRs are,
it may not be that useful in practice and less clean...

Cheers,
Ben. 

> ---
>  arch/powerpc/sysdev/dcr.c         |   91 ++++++++++++++++++++++++++++++++-----
>  include/asm-powerpc/dcr-generic.h |   49 ++++++++++++++++++++
>  include/asm-powerpc/dcr-mmio.h    |   20 +++++---
>  include/asm-powerpc/dcr-native.h  |   16 ++++---
>  include/asm-powerpc/dcr.h         |   36 ++++++++++++++-
>  5 files changed, 186 insertions(+), 26 deletions(-)
>  create mode 100644 include/asm-powerpc/dcr-generic.h
> 
> diff --git a/arch/powerpc/sysdev/dcr.c b/arch/powerpc/sysdev/dcr.c
> index 437e48d..d3de0ff 100644
> --- a/arch/powerpc/sysdev/dcr.c
> +++ b/arch/powerpc/sysdev/dcr.c
> @@ -23,6 +23,68 @@
>  #include <asm/prom.h>
>  #include <asm/dcr.h>
>  
> +#if defined(CONFIG_PPC_DCR_NATIVE) && defined(CONFIG_PPC_DCR_MMIO)
> +
> +bool dcr_map_ok_generic(dcr_host_t host)
> +{
> +	if (host.type == INVALID)
> +		return 0;
> +	else if (host.type == NATIVE)
> +		return dcr_map_ok_native(host.host.native);
> +	else
> +		return dcr_map_ok_mmio(host.host.mmio);
> +}
> +EXPORT_SYMBOL_GPL(dcr_map_ok_generic);
> +
> +dcr_host_t dcr_map_generic(struct device_node *dev,
> +			   unsigned int dcr_n,
> +			   unsigned int dcr_c)
> +{
> +	dcr_host_t host;
> +	const char *prop = of_get_property(dev, "dcr-access-method", NULL);
> +
> +	if (!strcmp(prop, "native")) {
> +		host.type = NATIVE;
> +		host.host.native = dcr_map_native(dev, dcr_n, dcr_c);
> +	} else if (!strcmp(prop, "mmio")) {
> +		host.type = MMIO;
> +		host.host.mmio = dcr_map_mmio(dev, dcr_n, dcr_c);
> +	} else
> +		host.type = INVALID;
> +
> +	return host;
> +}
> +EXPORT_SYMBOL_GPL(dcr_map_generic);
> +
> +void dcr_unmap_generic(dcr_host_t host, unsigned int dcr_c)
> +{
> +	if (host.type == NATIVE)
> +		dcr_unmap_native(host.host.native, dcr_c);
> +	else
> +		dcr_unmap_mmio(host.host.mmio, dcr_c);
> +}
> +EXPORT_SYMBOL_GPL(dcr_unmap_generic);
> +
> +u32 dcr_read_generic(dcr_host_t host, unsigned int dcr_n)
> +{
> +	if (host.type == NATIVE)
> +		return dcr_read_native(host.host.native, dcr_n);
> +	else
> +		return dcr_read_mmio(host.host.mmio, dcr_n);
> +}
> +EXPORT_SYMBOL_GPL(dcr_read_generic);
> +
> +void dcr_write_generic(dcr_host_t host, unsigned int dcr_n, u32 value)
> +{
> +	if (host.type == NATIVE)
> +		dcr_write_native(host.host.native, dcr_n, value);
> +	else
> +		dcr_write_mmio(host.host.mmio, dcr_n, value);
> +}
> +EXPORT_SYMBOL_GPL(dcr_write_generic);
> +
> +#endif /* defined(CONFIG_PPC_DCR_NATIVE) && defined(CONFIG_PPC_DCR_MMIO) */
> +
>  unsigned int dcr_resource_start(struct device_node *np, unsigned int index)
>  {
>  	unsigned int ds;
> @@ -47,7 +109,7 @@ unsigned int dcr_resource_len(struct device_node *np, unsigned int index)
>  }
>  EXPORT_SYMBOL_GPL(dcr_resource_len);
>  
> -#ifndef CONFIG_PPC_DCR_NATIVE
> +#ifdef CONFIG_PPC_DCR_MMIO
>  
>  static struct device_node * find_dcr_parent(struct device_node * node)
>  {
> @@ -101,18 +163,19 @@ u64 of_translate_dcr_address(struct device_node *dev,
>  	return ret;
>  }
>  
> -dcr_host_t dcr_map(struct device_node *dev, unsigned int dcr_n,
> -		   unsigned int dcr_c)
> +dcr_host_mmio_t dcr_map_mmio(struct device_node *dev,
> +			     unsigned int dcr_n,
> +			     unsigned int dcr_c)
>  {
> -	dcr_host_t ret = { .token = NULL, .stride = 0, .base = dcr_n };
> +	dcr_host_mmio_t ret = { .token = NULL, .stride = 0, .base = dcr_n };
>  	u64 addr;
>  
>  	pr_debug("dcr_map(%s, 0x%x, 0x%x)\n",
>  		 dev->full_name, dcr_n, dcr_c);
>  
>  	addr = of_translate_dcr_address(dev, dcr_n, &ret.stride);
> -	pr_debug("translates to addr: 0x%lx, stride: 0x%x\n",
> -		 addr, ret.stride);
> +	pr_debug("translates to addr: 0x%llx, stride: 0x%x\n",
> +		 (unsigned long long) addr, ret.stride);
>  	if (addr == OF_BAD_ADDR)
>  		return ret;
>  	pr_debug("mapping 0x%x bytes\n", dcr_c * ret.stride);
> @@ -124,11 +187,11 @@ dcr_host_t dcr_map(struct device_node *dev, unsigned int dcr_n,
>  	ret.token -= dcr_n * ret.stride;
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(dcr_map);
> +EXPORT_SYMBOL_GPL(dcr_map_mmio);
>  
> -void dcr_unmap(dcr_host_t host, unsigned int dcr_c)
> +void dcr_unmap_mmio(dcr_host_mmio_t host, unsigned int dcr_c)
>  {
> -	dcr_host_t h = host;
> +	dcr_host_mmio_t h = host;
>  
>  	if (h.token == NULL)
>  		return;
> @@ -136,7 +199,11 @@ void dcr_unmap(dcr_host_t host, unsigned int dcr_c)
>  	iounmap(h.token);
>  	h.token = NULL;
>  }
> -EXPORT_SYMBOL_GPL(dcr_unmap);
> -#else	/* defined(CONFIG_PPC_DCR_NATIVE) */
> +EXPORT_SYMBOL_GPL(dcr_unmap_mmio);
> +
> +#endif /* defined(CONFIG_PPC_DCR_MMIO) */
> +
> +#ifdef CONFIG_PPC_DCR_NATIVE
>  DEFINE_SPINLOCK(dcr_ind_lock);
> -#endif	/* !defined(CONFIG_PPC_DCR_NATIVE) */
> +#endif	/* defined(CONFIG_PPC_DCR_NATIVE) */
> +
> diff --git a/include/asm-powerpc/dcr-generic.h b/include/asm-powerpc/dcr-generic.h
> new file mode 100644
> index 0000000..0ee74fb
> --- /dev/null
> +++ b/include/asm-powerpc/dcr-generic.h
> @@ -0,0 +1,49 @@
> +/*
> + * (c) Copyright 2006 Benjamin Herrenschmidt, IBM Corp.
> + *                    <[email-masked]>
> + *
> + *   This program is free software;  you can redistribute it and/or modify
> + *   it under the terms of the GNU General Public License as published by
> + *   the Free Software Foundation; either version 2 of the License, or
> + *   (at your option) any later version.
> + *
> + *   This program is distributed in the hope that it will be useful,
> + *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
> + *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
> + *   the GNU General Public License for more details.
> + *
> + *   You should have received a copy of the GNU General Public License
> + *   along with this program;  if not, write to the Free Software
> + *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
> + */
> +
> +#ifndef _ASM_POWERPC_DCR_GENERIC_H
> +#define _ASM_POWERPC_DCR_GENERIC_H
> +#ifdef __KERNEL__
> +#ifndef __ASSEMBLY__
> +
> +enum host_type_t {MMIO, NATIVE, INVALID};
> +
> +typedef struct {
> +	enum host_type_t type;
> +	union {
> +		dcr_host_mmio_t mmio;
> +		dcr_host_native_t native;
> +	} host;
> +} dcr_host_t;
> +
> +extern bool dcr_map_ok_generic(dcr_host_t host);
> +
> +extern dcr_host_t dcr_map_generic(struct device_node *dev, unsigned int dcr_n,
> +			  unsigned int dcr_c);
> +extern void dcr_unmap_generic(dcr_host_t host, unsigned int dcr_c);
> +
> +extern u32 dcr_read_generic(dcr_host_t host, unsigned int dcr_n);
> +
> +extern void dcr_write_generic(dcr_host_t host, unsigned int dcr_n, u32 value);
> +
> +#endif /* __ASSEMBLY__ */
> +#endif /* __KERNEL__ */
> +#endif /* _ASM_POWERPC_DCR_GENERIC_H */
> +
> +
> diff --git a/include/asm-powerpc/dcr-mmio.h b/include/asm-powerpc/dcr-mmio.h
> index 08532ff..acd491d 100644
> --- a/include/asm-powerpc/dcr-mmio.h
> +++ b/include/asm-powerpc/dcr-mmio.h
> @@ -27,20 +27,26 @@ typedef struct {
>  	void __iomem *token;
>  	unsigned int stride;
>  	unsigned int base;
> -} dcr_host_t;
> +} dcr_host_mmio_t;
>  
> -#define DCR_MAP_OK(host)	((host).token != NULL)
> +static inline bool dcr_map_ok_mmio(dcr_host_mmio_t host)
> +{
> +	return host.token != NULL;
> +}
>  
> -extern dcr_host_t dcr_map(struct device_node *dev, unsigned int dcr_n,
> -			  unsigned int dcr_c);
> -extern void dcr_unmap(dcr_host_t host, unsigned int dcr_c);
> +extern dcr_host_mmio_t dcr_map_mmio(struct device_node *dev,
> +				    unsigned int dcr_n,
> +				    unsigned int dcr_c);
> +extern void dcr_unmap_mmio(dcr_host_mmio_t host, unsigned int dcr_c);
>  
> -static inline u32 dcr_read(dcr_host_t host, unsigned int dcr_n)
> +static inline u32 dcr_read_mmio(dcr_host_mmio_t host, unsigned int dcr_n)
>  {
>  	return in_be32(host.token + ((host.base + dcr_n) * host.stride));
>  }
>  
> -static inline void dcr_write(dcr_host_t host, unsigned int dcr_n, u32 value)
> +static inline void dcr_write_mmio(dcr_host_mmio_t host,
> +				  unsigned int dcr_n,
> +				  u32 value)
>  {
>  	out_be32(host.token + ((host.base + dcr_n) * host.stride), value);
>  }
> diff --git a/include/asm-powerpc/dcr-native.h b/include/asm-powerpc/dcr-native.h
> index be6c879..67832e5 100644
> --- a/include/asm-powerpc/dcr-native.h
> +++ b/include/asm-powerpc/dcr-native.h
> @@ -26,14 +26,18 @@
>  
>  typedef struct {
>  	unsigned int base;
> -} dcr_host_t;
> +} dcr_host_native_t;
>  
> -#define DCR_MAP_OK(host)	(1)
> +static inline bool dcr_map_ok_native(dcr_host_native_t host)
> +{
> +	return 1;
> +}
>  
> -#define dcr_map(dev, dcr_n, dcr_c)	((dcr_host_t){ .base = (dcr_n) })
> -#define dcr_unmap(host, dcr_c)		do {} while (0)
> -#define dcr_read(host, dcr_n)		mfdcr(dcr_n + host.base)
> -#define dcr_write(host, dcr_n, value)	mtdcr(dcr_n + host.base, value)
> +#define dcr_map_native(dev, dcr_n, dcr_c) \
> +	((dcr_host_native_t){ .base = (dcr_n) })
> +#define dcr_unmap_native(host, dcr_c)		do {} while (0)
> +#define dcr_read_native(host, dcr_n)		mfdcr(dcr_n + host.base)
> +#define dcr_write_native(host, dcr_n, value)	mtdcr(dcr_n + host.base, value)
>  
>  /* Device Control Registers */
>  void __mtdcr(int reg, unsigned int val);
> diff --git a/include/asm-powerpc/dcr.h b/include/asm-powerpc/dcr.h
> index 9338d50..6b86322 100644
> --- a/include/asm-powerpc/dcr.h
> +++ b/include/asm-powerpc/dcr.h
> @@ -20,14 +20,47 @@
>  #ifndef _ASM_POWERPC_DCR_H
>  #define _ASM_POWERPC_DCR_H
>  #ifdef __KERNEL__
> +#ifndef __ASSEMBLY__
>  #ifdef CONFIG_PPC_DCR
>  
>  #ifdef CONFIG_PPC_DCR_NATIVE
>  #include <asm/dcr-native.h>
> -#else
> +#endif
> +
> +#ifdef CONFIG_PPC_DCR_MMIO
>  #include <asm/dcr-mmio.h>
>  #endif
>  
> +#if defined(CONFIG_PPC_DCR_NATIVE) && defined(CONFIG_PPC_DCR_MMIO)
> +
> +#include <asm/dcr-generic.h>
> +
> +#define DCR_MAP_OK(host)	dcr_map_ok_generic(host)
> +#define dcr_map(dev, dcr_n, dcr_c) dcr_map_generic(dev, dcr_n, dcr_c)
> +#define dcr_unmap(host, dcr_c) dcr_unmap_generic(host, dcr_c)
> +#define dcr_read(host, dcr_n) dcr_read_generic(host, dcr_n)
> +#define dcr_write(host, dcr_n, value) dcr_write_generic(host, dcr_n, value)
> +
> +#else
> +
> +#ifdef CONFIG_PPC_DCR_NATIVE
> +typedef dcr_host_native_t dcr_host_t;
> +#define DCR_MAP_OK(host)	dcr_map_ok_native(host)
> +#define dcr_map(dev, dcr_n, dcr_c) dcr_map_native(dev, dcr_n, dcr_c)
> +#define dcr_unmap(host, dcr_c) dcr_unmap_native(host, dcr_c)
> +#define dcr_read(host, dcr_n) dcr_read_native(host, dcr_n)
> +#define dcr_write(host, dcr_n, value) dcr_write_native(host, dcr_n, value)
> +#else
> +typedef dcr_host_mmio_t dcr_host_t;
> +#define DCR_MAP_OK(host)	dcr_map_ok_mmio(host)
> +#define dcr_map(dev, dcr_n, dcr_c) dcr_map_mmio(dev, dcr_n, dcr_c)
> +#define dcr_unmap(host, dcr_c) dcr_unmap_mmio(host, dcr_c)
> +#define dcr_read(host, dcr_n) dcr_read_mmio(host, dcr_n)
> +#define dcr_write(host, dcr_n, value) dcr_write_mmio(host, dcr_n, value)
> +#endif
> +
> +#endif /* defined(CONFIG_PPC_DCR_NATIVE) && defined(CONFIG_PPC_DCR_MMIO) */
> +
>  /*
>   * On CONFIG_PPC_MERGE, we have additional helpers to read the DCR
>   * base from the device-tree
> @@ -41,5 +74,6 @@ extern unsigned int dcr_resource_len(struct device_node *np,
>  #endif /* CONFIG_PPC_MERGE */
>  
>  #endif /* CONFIG_PPC_DCR */
> +#endif /* __ASSEMBLY__ */
>  #endif /* __KERNEL__ */
>  #endif /* _ASM_POWERPC_DCR_H */