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Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation
From: |
Bystricky, Juro |
Subject: |
Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation |
Date: |
Thu, 9 Feb 2017 16:07:53 +0000 |
> >> [...]
> >>
> >>>>> +static uint64_t altera_juart_read(void *opaque, hwaddr addr,
> unsigned
> >>>> int size)
> >>>>> +{
> >>>>> + AlteraJUARTState *s = opaque;
> >>>>> + uint32_t r;
> >>>>> +
> >>>>> + addr >>= 2;
> >>>>
> >>>> Hmmmmm, how will unaligned read from one of these registers be handled
> >>>> on real HW ? ie. read from address 0x3 ? What about writes ?
> >>>>
> >>>
> >>> there is no reading/writing going on via "addr".
> >>> This just maps the hw address into register number, where registers are
> >> at
> >>> 4 bytes boundaries (so they are aligned as needed) but indexed as
> >> 1,2,3....
> >>> (Pretty common code in other drivers.)
> >>> But will redo the code anyway so there are no shifts.
> >>
> >> This doesn't answer my question at all. How does real hardware behave if
> >> you read from unaligned address in the register space , ie. offset 0x3 ?
> >>
> >
> > Not sure I understand the question here. Which "real hardware" are we
> talking about?
>
> By real hardware I mean real Nios2 system ...
>
> > If "real hardware" contains MMU or MPU then an exception is generated on
> misalign access.
>
> Is this handled here or not ?
>
Sorry, I am not sure I understand the question.
Exceptions are handled by interrupt controller.
This code for JTAG UART does not have any misaligned accesses.
- [Qemu-devel] [PATCH v3 0/1] nios2: Add Altera JTAG UART emulation, Juro Bystricky, 2017/02/08
- [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Juro Bystricky, 2017/02/08
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Marek Vasut, 2017/02/08
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Peter Maydell, 2017/02/08
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Bystricky, Juro, 2017/02/08
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Marek Vasut, 2017/02/09
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Bystricky, Juro, 2017/02/09
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Marek Vasut, 2017/02/09
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation,
Bystricky, Juro <=
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Marek Vasut, 2017/02/09
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Bystricky, Juro, 2017/02/09
- Re: [Qemu-devel] [PATCH v3 1/1] nios2: Add Altera JTAG UART emulation, Marek Vasut, 2017/02/09