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Date:   Mon, 27 Apr 2020 19:03:40 +0800
From:   Jiaxun Yang <jiaxun.yang@flygoat.com>
To:     John Garry <john.garry@huawei.com>, linux-mips@vger.kernel.org
CC:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Huacai Chen <chenhc@lemote.com>,
        Paul Burton <paulburton@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Stephen Kitt <steve@sk2.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Serge Semin <fancer.lancer@gmail.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Daniel Silsby <dansilsby@gmail.com>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Paul Cercueil <paul@crapouillou.net>,
        Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Allison Randal <allison@lohutok.net>,
        Tiezhu Yang <yangtiezhu@loongson.cn>,
        Wei Xu <xuwei5@hisilicon.com>, linux-kernel@vger.kernel.org,
        Arnd Bergmann <arnd@arndb.de>, Linuxarm <linuxarm@huawei.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Rob Herring <robh@kernel.org>
Subject: Re: [PATCH 3/4] lib: logic_pio: Introduce MMIO_LOWER_RESERVED
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=E4=BA=8E 2020=E5=B9=B44=E6=9C=8827=E6=97=A5 GMT+08:00 =E4=B8=8B=E5=8D=886=
:43:09, John Garry <john=2Egarry@huawei=2Ecom> =E5=86=99=E5=88=B0:
>On 26/04/2020 12:47, Jiaxun Yang wrote:
>> That would allow platforms reserve some lower address in PIO MMIO range
>> to deal with legacy drivers with hardcoded I/O ports that can't be
>> managed by logic_pio=2E
>
>Hi,
>
>Is there some reason why the logic_pio code cannot be improved to handle=
=20
>these devices at these "fixed" addresses? Or do you have a plan to=20
>improve it? We already support fixed bus address devices in the INDIRECT=
=20
>IO region=2E

Hi,

The issue about "Fixed Address" is we can't control the ioport
That driver used to operate devices=2E
So any attempt to resolve it in logic_pio seems impossible=2E

Currently we have i8259, i8042, piix4_smbus, mc146818 rely on this assumpt=
ion=2E

My plan is after getting this part merged, I'm going to work on a ISA Host=
 bridge driver,
then convert device drivers into logic_pio and Devicetree based driver ste=
p by step=2E

Finally when we nologner have any legacy driver, we can safely remove this=
 reserved
range=2E

Thanks=2E


>
>Carving out a region of IO space is less than ideal=2E
>
>Thanks,
>John
>
>>=20
>> Signed-off-by: Jiaxun Yang <jiaxun=2Eyang@flygoat=2Ecom>
>> ---
>>   lib/logic_pio=2Ec | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>=20
>> diff --git a/lib/logic_pio=2Ec b/lib/logic_pio=2Ec
>> index f511a99bb389=2E=2E57fff1cb7063 100644
>> --- a/lib/logic_pio=2Ec
>> +++ b/lib/logic_pio=2Ec
>> @@ -20,6 +20,10 @@
>>   static LIST_HEAD(io_range_list);
>>   static DEFINE_MUTEX(io_range_mutex);
>>  =20
>> +#ifndef MMIO_LOWER_RESERVED
>> +#define MMIO_LOWER_RESERVED	0
>> +#endif
>> +
>>   /* Consider a kernel general helper for this */
>>   #define in_range(b, first, len)        ((b) >=3D (first) && (b) < (fi=
rst) + (len))
>>  =20
>> @@ -36,7 +40,7 @@ int logic_pio_register_range(struct logic_pio_hwaddr =
*new_range)
>>   	struct logic_pio_hwaddr *range;
>>   	resource_size_t start;
>>   	resource_size_t end;
>> -	resource_size_t mmio_end =3D 0;
>> +	resource_size_t mmio_end =3D MMIO_LOWER_RESERVED;
>>   	resource_size_t iio_sz =3D MMIO_UPPER_LIMIT;
>>   	int ret =3D 0;
>>  =20
>>=20
>

--=20
Jiaxun Yang