linux-kernel - Re: [PATCH -next] drivers/video/fbdev: Add dependencies on !S390

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Message-ID: <55DE1C2B.90802@roeck-us.net>
Date:	Wed, 26 Aug 2015 13:06:03 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
CC:	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Borislav Petkov <bp@...e.de>, Ingo Molnar <mingo@...nel.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH -next] drivers/video/fbdev: Add dependencies on !S390

Hi Luis,

On 08/26/2015 12:48 PM, Luis R. Rodriguez wrote:
>
> Hey Guenter,
>
> thanks so much for your patch, my feedback below! I'll proactively
> Cc Andrew and Steven as they're the other ones who I've seen as
> hawks to compile issues on linux-next so I expect they'll soon
> run into this as well if they are also testing against s390.
>
> On Wed, Aug 26, 2015 at 04:32:50AM -0700, Guenter Roeck wrote:
>> s390:allmodconfig fails to build with:
>>
>> ERROR: "pci_iomap_wc" [drivers/video/fbdev/vt8623fb.ko] undefined!
>> ERROR: "pci_iomap_wc" [drivers/video/fbdev/s3fb.ko] undefined!
>> ERROR: "pci_iomap_wc" [drivers/video/fbdev/arkfb.ko] undefined!
>>
>> Those functions are currently only available in generic PCI iomap code,
>> which is not used on S390.
>>
>> Fixes: 81bdef04d3bc ("drivers/video/fbdev/vt8623fb: Use arch_phys_wc_add() and pci_iomap_wc()")
>> Fixes: 4edcd2ab1255 ("drivers/video/fbdev/s3fb: Use arch_phys_wc_add() and pci_iomap_wc()")
>> Fixes: c823a48ac47f ("drivers/video/fbdev/arkfb.c: Use arch_phys_wc_add() and pci_iomap_wc()")
>
> Those commit IDs are only sepcific to linux-next and as such are
> ephemeral.
>
Depends on the introducing tree.

>> Cc: Luis R. Rodriguez <mcgrof@...e.com>
>> Cc: Borislav Petkov <bp@...e.de>
>> Cc: Ingo Molnar <mingo@...nel.org>
>> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>> ---
>>   drivers/video/fbdev/Kconfig | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
>> index 8b1d371b5404..6b1893e5c769 100644
>> --- a/drivers/video/fbdev/Kconfig
>> +++ b/drivers/video/fbdev/Kconfig
>> @@ -1442,6 +1442,7 @@ config FB_ATY_BACKLIGHT
>>   config FB_S3
>>   	tristate "S3 Trio/Virge support"
>>   	depends on FB && PCI
>> +	depends on !S390
>>   	select FB_CFB_FILLRECT
>>   	select FB_CFB_COPYAREA
>>   	select FB_CFB_IMAGEBLIT
>> @@ -1649,6 +1650,7 @@ config FB_VOODOO1
>>   config FB_VT8623
>>   	tristate "VIA VT8623 support"
>>   	depends on FB && PCI
>> +	depends on !S390
>>   	select FB_CFB_FILLRECT
>>   	select FB_CFB_COPYAREA
>>   	select FB_CFB_IMAGEBLIT
>> @@ -1683,6 +1685,7 @@ config FB_TRIDENT
>>   config FB_ARK
>>   	tristate "ARK 2000PV support"
>>   	depends on FB && PCI
>> +	depends on !S390
>>   	select FB_CFB_FILLRECT
>>   	select FB_CFB_COPYAREA
>>   	select FB_CFB_IMAGEBLIT
>
> Although this is one way to resolve it, the patch does not explain why
> its needed, and this would also mean its a reactive solution, we either
> test-compile and find issues or expect and hope developers will also
> annotate this themselves when using this new API. I rather we define
> it S390, which I do below.
>
> The reason S390 requires its own S390 requires its own pci_iomap*()
> calls is because it has its "BAR spaces are not disjunctive on s390
> so we need the bar parameter of pci_iomap to find the corresponding
> device and create the mapping cookie." but in summary, it has its own
> lookup/lock solution. It does not include asm-generic/pci_iomap.h
> and requires implementing the generic solutoins on its own then.
>
> As for write-combining, it has no specific solution for this so
> its ioremap_wc() is a direct mapping, so we can just do a 1-1
> mapping to the non-wc calls as well then. If we do this then we
> don't have to go on fixing drivers when they use this new API and
> if and when S390 gets some form of WC it can go and update its
> implementation but right now it has none.
>
> I've tested the patch below on linux-next with make.cross ARCH=s390
> with allyesconfig and it fixes the compile issue. I'll post this as
> a patch fix. Let me know if this is agreeable to you.
>

Sure, go ahead. It is a much better solution than mine, after all.

Guenter

> diff --git a/arch/s390/include/asm/io.h b/arch/s390/include/asm/io.h
> index cb5fdf3a78fc..437e9af96688 100644
> --- a/arch/s390/include/asm/io.h
> +++ b/arch/s390/include/asm/io.h
> @@ -57,6 +57,8 @@ static inline void ioport_unmap(void __iomem *p)
>    */
>   #define pci_iomap pci_iomap
>   #define pci_iounmap pci_iounmap
> +#define pci_iomap_wc pci_iomap
> +#define pci_iomap_wc_range pci_iomap_range
>
>   #define memcpy_fromio(dst, src, count)	zpci_memcpy_fromio(dst, src, count)
>   #define memcpy_toio(dst, src, count)	zpci_memcpy_toio(dst, src, count)
>

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