[Qemu-devel] Re: [RFC][PATCH 4/4] Add support for Marvell 88w8618 / MusicPal

[Jan Kiszka <jan.kiszka@web.de>]

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andrzej zaborowski wrote:
> Hi,
> 
> On 13/04/2008, Jan Kiszka <jan.kiszka@web.de> wrote:
>> This is the board emulation for Freecom's MusicPal, featuring
>>   - rudimentary PIT and PIC
>>   - up to 2 UARTs
>>   - 88W8xx8 Ethernet controller
>>   - 88W8618 audio controller
>>   - Wolfson WM8750 mixer chip (volume control and mute only)
> 
> Are you sure that hw/wm8750.c is not reusable?  It's probably better
> to extend it with volume control, and audio data transmission through
> i2c, instead of having two implementations in QEMU.

Will check again, but I don't think it is helpful, at least at this
point. The thing is that the MusicPal uses the on-chip DAC, not the one
of the Wolfson. The latter seems to be responsible for analogous mixing
only.

> 
> Regarding volume control, since there are only 0x7f possible values
> it's nicer to use a const table than pull in math.h.  Actually I
> wouldn't worry about that at all because the layout of volume levels
> on the host is not guaranteed to be linear (I think?), it may very
> well be already exponential.  For example the Linux WM8750 driver
> doesn't do the reverse transformation which would mean that on a host
> whose ALSA output device is a WM8750, the Qemu vm would have a wrong
> volume scale.

[ Ignoring the above as advised in the follow-up, but will think about
avoiding or reducing the usage of pow(). ]

> 
>>   - 128×64 display with brightness control
>>   - all input buttons
>>
>>  Using up to 32 MB flash, I hit a limit /wrt phys_ram_size. I worked
>>  around this for now by extending MAX_BIOS_SIZE to 32 MB, surely not a
>>  nice solution.
> 
> You can use -m 150 or similar.
> 
> Please also format the code similarly to rest of Qemu.

That would just increase ram_size, thus won't help as I need memory
beyond it (here for the pflash in R/W mode).

Jan


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