Re: [PATCH 2/6] dp8393x: don't force 32-bit register access

[Philippe Mathieu-Daudé]

On 7/3/21 4:39 PM, Mark Cave-Ayland wrote:
> On 03/07/2021 15:19, Philippe Mathieu-Daudé wrote:
> 
>> From: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>>
>> Commit 3fe9a838ec "dp8393x: Always use 32-bit accesses" assumed that
>> all accesses
>> to the registers were 32-bit but this is actually not the case. The
>> access size is
>> determined by the CPU instruction used and not the number of physical
>> address lines.
>>
>> The big_endian workaround applied to the register read/writes was
>> actually caused
>> by forcing the access size to 32-bit when the guest OS was using a
>> 16-bit access.
>> Since the registers are 16-bit then we can simply set .impl.min_access
>> to 2 and
>> then the memory API will automatically do the right thing for both
>> 16-bit accesses
>> used by Linux and 32-bit accesses used by the MacOS toolbox ROM.
> 
> The change should work, but the commit message above needs a slight
> tweak - maybe something like this?
> 
> Since the registers are 16-bit then we can simply set both
> .impl.min_access and .impl.max_access to 2 and then the memory API will
> automatically do the right thing for both 16-bit accesses used by Linux
> and 32-bit accesses used by the MacOS toolbox ROM.

Do you mind sending v3 of this patch reworded (and including the .valid
fields)?

>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>> Fixes: 3fe9a838ec ("dp8393x: Always use 32-bit accesses")
>> Tested-by: Finn Thain <fthain@linux-m68k.org>
>> Message-Id: <20210625065401.30170-9-mark.cave-ayland@ilande.co.uk>
>> [PMD: dp8393x_ops.impl.max_access_size 4 -> 2]
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>>   hw/net/dp8393x.c | 9 ++++-----
>>   1 file changed, 4 insertions(+), 5 deletions(-)