Re: [Xen-devel] [RFC PATCHv1] serial: Support OXPCIe952 aka Oxford Semiconductor Ltd Device c138 (1415:c138)

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.03.14 at 14:29, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
> On Tue, Mar 04, 2014 at 10:57:08AM +0000, Jan Beulich wrote:
>> >>> On 04.03.14 at 11:36, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 
>> >>> wrote:
>> 
>> > On Mar 4, 2014 4:43 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> >>
>> >> >>> On 04.03.14 at 03:01, Konrad Rzeszutek Wilk <konrad@xxxxxxxxxx> 
>> >> >>> wrote: 
>> >> > @@ -325,11 +342,12 @@ static void __init ns16550_init_preirq(struct 
>> > serial_port *port) 
>> >> >  #ifdef CONFIG_X86 
>> >> >          enum fixed_addresses idx = FIX_COM_BEGIN + (uart - 
>> >> > ns16550_com); 
>> >> >  
>> >> > -        set_fixmap_nocache(idx, uart->io_base); 
>> >> > +        set_fixmap_nocache(idx, uart->io_base + uart->offset); 
>> >> >          uart->remapped_io_base = (void __iomem *)fix_to_virt(idx); 
>> >> >          uart->remapped_io_base += uart->io_base & ~PAGE_MASK; 
>> >>
>> >> Don't you need to add in uart->offset here too?
>> > 
>> > The virtual address at that point already covers then BAR + offset.
>> 
>> Hardly: fix_to_virt() returns a page-aligned address, and anything
>> that may affect the offset-in-page value needs to be taken into
>> consideration in the right side expression of the +=.
> 
> Oh, this is not a offset-in-page (well, it is, but also past the first
> page). In this case the offset ends up being BAR + 0x1000 + 0x200 * idx.
> It is well past the first page.
> 
> Perhaps splitting it up in two offsets would be better?
> 
>       set_fixmap_nocache(idx, uart_io_base + uart->pfn_offset * PAGE_SIZE);
>       uart->remapped_io_base = (void __iomem)*fix_to_virt(idx);
>       uart->remapped_io_base += uart->io_base + uart->offset & ~PAGE_MASK;
> 
> And of course we make sure that offset is within 0->4096.

I don't think that makes sense. Just properly add uart->offset as
indicated.

Jan


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