Re: [Xen-devel] [PATCH V2 3/3] xen/arm: Add SCIFA UART support for early printk

[Julien Grall <julien.grall@xxxxxxx>]

Hi Oleksandr,

On 2/18/19 8:45 PM, Oleksandr wrote:
> On 18.02.19 22:41, Oleksandr wrote:
> > On 18.02.19 16:05, Julien Grall wrote:
> > > Hi,
> >
> > Hi
> >
> >
> > > On 01/02/2019 12:37, Oleksandr Tyshchenko wrote:
> > > > From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
> > > >
> > > > Add support for Renesas "Stout" development board based on
> > > > R-Car H2 SoC which has SCIFA compatible UART.
> > > >
> > > > Actually existing SCIF UART support (debug-scif.inc) and
> > > > newly added SCIFA UART support (debug-scifa.inc) differ only
> > > > in registers offsets.
> > > Can we try to merge the two then? One solution is to provide another 
> > > options similar to how we deal with REG_SHIFT on the 8250.
> >
> > Actually, the main difference for the "early printk" support is in two 
> > reg offsets:
> > +#define SCIFA_SCASSR   0x14    /* Serial status register */
> > +#define SCIFA_SCAFTDR  0x20    /* Transmit FIFO data register */
> >
> > +#define SCIF_SCFSR             0x10    /* Serial status register */
> > +#define SCIF_SCFTDR            0x0c    /* Transmit FIFO data register */
> >
> >
> > I am not mistaken, we will have to introduce two options to cover this 
> > case, as the offsets are not correlated with each other, no?
You don't need two options. For instance, you can only introduce an 
option SCIF_VERSION that would be 0 for SCIF and 61 (ascii 'a') for SCIFA.
Then in the code, you can use SCIF_VERSION to decides which sets of 
macros you are using.
Cheers,

--
Julien Grall

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