linux-kernel - Re: [PATCH] x86/PCI: simplify pci_bios

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Date:	Wed, 9 Dec 2015 10:50:46 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Geliang Tang <geliangtang@....com>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/PCI: simplify pci_bios_{read,write}

On Mon, Dec 07, 2015 at 10:24:24PM +0800, Geliang Tang wrote:
> There are some repetitive code in the switch/case statement in
> pci_bios_read() and pci_bios_write(). I drop it to simplify the
> code.
> 
> Signed-off-by: Geliang Tang <geliangtang@....com>

Applied to pci/misc for v4.5 with Thomas' Reviewed-by, thanks!

> ---
>  arch/x86/pci/pcbios.c | 108 ++++++++++++++++++--------------------------------
>  1 file changed, 38 insertions(+), 70 deletions(-)
> 
> diff --git a/arch/x86/pci/pcbios.c b/arch/x86/pci/pcbios.c
> index 9b83b90..9770e55 100644
> --- a/arch/x86/pci/pcbios.c
> +++ b/arch/x86/pci/pcbios.c
> @@ -180,6 +180,7 @@ static int pci_bios_read(unsigned int seg, unsigned int bus,
>  	unsigned long result = 0;
>  	unsigned long flags;
>  	unsigned long bx = (bus << 8) | devfn;
> +	u16 number = 0, mask = 0;
>  
>  	WARN_ON(seg);
>  	if (!value || (bus > 255) || (devfn > 255) || (reg > 255))
> @@ -189,53 +190,35 @@ static int pci_bios_read(unsigned int seg, unsigned int bus,
>  
>  	switch (len) {
>  	case 1:
> -		__asm__("lcall *(%%esi); cld\n\t"
> -			"jc 1f\n\t"
> -			"xor %%ah, %%ah\n"
> -			"1:"
> -			: "=c" (*value),
> -			  "=a" (result)
> -			: "1" (PCIBIOS_READ_CONFIG_BYTE),
> -			  "b" (bx),
> -			  "D" ((long)reg),
> -			  "S" (&pci_indirect));
> -		/*
> -		 * Zero-extend the result beyond 8 bits, do not trust the
> -		 * BIOS having done it:
> -		 */
> -		*value &= 0xff;
> +		number = PCIBIOS_READ_CONFIG_BYTE;
> +		mask = 0xff;
>  		break;
>  	case 2:
> -		__asm__("lcall *(%%esi); cld\n\t"
> -			"jc 1f\n\t"
> -			"xor %%ah, %%ah\n"
> -			"1:"
> -			: "=c" (*value),
> -			  "=a" (result)
> -			: "1" (PCIBIOS_READ_CONFIG_WORD),
> -			  "b" (bx),
> -			  "D" ((long)reg),
> -			  "S" (&pci_indirect));
> -		/*
> -		 * Zero-extend the result beyond 16 bits, do not trust the
> -		 * BIOS having done it:
> -		 */
> -		*value &= 0xffff;
> +		number = PCIBIOS_READ_CONFIG_WORD;
> +		mask = 0xffff;
>  		break;
>  	case 4:
> -		__asm__("lcall *(%%esi); cld\n\t"
> -			"jc 1f\n\t"
> -			"xor %%ah, %%ah\n"
> -			"1:"
> -			: "=c" (*value),
> -			  "=a" (result)
> -			: "1" (PCIBIOS_READ_CONFIG_DWORD),
> -			  "b" (bx),
> -			  "D" ((long)reg),
> -			  "S" (&pci_indirect));
> +		number = PCIBIOS_READ_CONFIG_DWORD;
>  		break;
>  	}
>  
> +	__asm__("lcall *(%%esi); cld\n\t"
> +		"jc 1f\n\t"
> +		"xor %%ah, %%ah\n"
> +		"1:"
> +		: "=c" (*value),
> +		  "=a" (result)
> +		: "1" (number),
> +		  "b" (bx),
> +		  "D" ((long)reg),
> +		  "S" (&pci_indirect));
> +	/*
> +	 * Zero-extend the result beyond 8 or 16 bits, do not trust the
> +	 * BIOS having done it:
> +	 */
> +	if (mask)
> +		*value &= mask;
> +
>  	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
>  
>  	return (int)((result & 0xff00) >> 8);
> @@ -247,6 +230,7 @@ static int pci_bios_write(unsigned int seg, unsigned int bus,
>  	unsigned long result = 0;
>  	unsigned long flags;
>  	unsigned long bx = (bus << 8) | devfn;
> +	u16 number = 0;
>  
>  	WARN_ON(seg);
>  	if ((bus > 255) || (devfn > 255) || (reg > 255)) 
> @@ -256,43 +240,27 @@ static int pci_bios_write(unsigned int seg, unsigned int bus,
>  
>  	switch (len) {
>  	case 1:
> -		__asm__("lcall *(%%esi); cld\n\t"
> -			"jc 1f\n\t"
> -			"xor %%ah, %%ah\n"
> -			"1:"
> -			: "=a" (result)
> -			: "0" (PCIBIOS_WRITE_CONFIG_BYTE),
> -			  "c" (value),
> -			  "b" (bx),
> -			  "D" ((long)reg),
> -			  "S" (&pci_indirect));
> +		number = PCIBIOS_WRITE_CONFIG_BYTE;
>  		break;
>  	case 2:
> -		__asm__("lcall *(%%esi); cld\n\t"
> -			"jc 1f\n\t"
> -			"xor %%ah, %%ah\n"
> -			"1:"
> -			: "=a" (result)
> -			: "0" (PCIBIOS_WRITE_CONFIG_WORD),
> -			  "c" (value),
> -			  "b" (bx),
> -			  "D" ((long)reg),
> -			  "S" (&pci_indirect));
> +		number = PCIBIOS_WRITE_CONFIG_WORD;
>  		break;
>  	case 4:
> -		__asm__("lcall *(%%esi); cld\n\t"
> -			"jc 1f\n\t"
> -			"xor %%ah, %%ah\n"
> -			"1:"
> -			: "=a" (result)
> -			: "0" (PCIBIOS_WRITE_CONFIG_DWORD),
> -			  "c" (value),
> -			  "b" (bx),
> -			  "D" ((long)reg),
> -			  "S" (&pci_indirect));
> +		number = PCIBIOS_WRITE_CONFIG_DWORD;
>  		break;
>  	}
>  
> +	__asm__("lcall *(%%esi); cld\n\t"
> +		"jc 1f\n\t"
> +		"xor %%ah, %%ah\n"
> +		"1:"
> +		: "=a" (result)
> +		: "0" (number),
> +		  "c" (value),
> +		  "b" (bx),
> +		  "D" ((long)reg),
> +		  "S" (&pci_indirect));
> +
>  	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
>  
>  	return (int)((result & 0xff00) >> 8);
> -- 
> 2.5.0
> 
> 
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