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From: Robin Murphy <robin.murphy@arm.com>
To: Mark Rutland <mark.rutland@arm.com>, Geoff Levand <geoff@infradead.org>
Cc: Pratyush Anand <panand@redhat.com>,
	AKASHI Takahiro <takahiro.akashi@linaro.org>,
	Simon Horman <horms@verge.net.au>,
	kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v1 3/4] arm64: Add arm64 kexec support
Date: Thu, 21 Jul 2016 11:50:42 +0100	[thread overview]
Message-ID: <5790A902.6070601@arm.com> (raw)
In-Reply-To: <20160721103120.GB20559@leverpostej>

On 21/07/16 11:31, Mark Rutland wrote:
[...]
>>>> +
>>>> +> > 	> > if (*p == 0)
>>>> +> > 	> > 	> > return 0;
>>>> +
>>>> +> > 	> > errno = 0;
>>>> +
>>>> +> > 	> > v = strtoull(p, NULL, 0);
>>>> +
>>>> +> > 	> > if (errno)
>>>> +> > 	> > 	> > return 0;
>>>> +
>>>> +> > 	> > return v;
>>>> +}
>>>
>>> It looks like the purgatory code expects angel SWI as the earlycon,
>>
>> Maybe you saw the debug_brk macro in entry.S?  I should remove
>> that and just loop.
> 
> Ah, sorry. For some reason I got that confused with the sink code. My
> bad.
> 
> Now I see that's assuming an 8-bit MMIO register.
> 
>>> whereas many other earlycons exist (with pl011 being extremely popular).
>>> Regardless, if we assume a particular UART type, we should explicitly
>>> verify that here. Otherwise the purgatory code will likely bring down
>>> the system, and it will be very painful to debug.
>>>
>>> Please explicitly check for the supported earlycon name.
>>
>> Purgatory just writes bytes to the address given.  Are there
>> UARTs that don't have TX as the first port?
> 
> I'm not sure, but it's certainly possible. The generic earlycon binding
> doesn't guarantee that the first address is a TX register. Even if they
> don't exist today, they could in a month's time, so I don't think we
> should assume anything.

The Exynos UART (drivers/tty/serial/samsung.c) is one which comes to
mind as definitely existing, and on arm64 systems to boot. The TX
register is at offset 0x20 there.

Robin.

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WARNING: multiple messages have this Message-ID (diff)
From: robin.murphy@arm.com (Robin Murphy)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v1 3/4] arm64: Add arm64 kexec support
Date: Thu, 21 Jul 2016 11:50:42 +0100	[thread overview]
Message-ID: <5790A902.6070601@arm.com> (raw)
In-Reply-To: <20160721103120.GB20559@leverpostej>

On 21/07/16 11:31, Mark Rutland wrote:
[...]
>>>> +
>>>> +> > 	> > if (*p == 0)
>>>> +> > 	> > 	> > return 0;
>>>> +
>>>> +> > 	> > errno = 0;
>>>> +
>>>> +> > 	> > v = strtoull(p, NULL, 0);
>>>> +
>>>> +> > 	> > if (errno)
>>>> +> > 	> > 	> > return 0;
>>>> +
>>>> +> > 	> > return v;
>>>> +}
>>>
>>> It looks like the purgatory code expects angel SWI as the earlycon,
>>
>> Maybe you saw the debug_brk macro in entry.S?  I should remove
>> that and just loop.
> 
> Ah, sorry. For some reason I got that confused with the sink code. My
> bad.
> 
> Now I see that's assuming an 8-bit MMIO register.
> 
>>> whereas many other earlycons exist (with pl011 being extremely popular).
>>> Regardless, if we assume a particular UART type, we should explicitly
>>> verify that here. Otherwise the purgatory code will likely bring down
>>> the system, and it will be very painful to debug.
>>>
>>> Please explicitly check for the supported earlycon name.
>>
>> Purgatory just writes bytes to the address given.  Are there
>> UARTs that don't have TX as the first port?
> 
> I'm not sure, but it's certainly possible. The generic earlycon binding
> doesn't guarantee that the first address is a TX register. Even if they
> don't exist today, they could in a month's time, so I don't think we
> should assume anything.

The Exynos UART (drivers/tty/serial/samsung.c) is one which comes to
mind as definitely existing, and on arm64 systems to boot. The TX
register is at offset 0x20 there.

Robin.

  reply	other threads:[~2016-07-21 10:50 UTC|newest]

Thread overview: 90+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-19 23:28 [PATCH v1 0/4] arm64 kexec-tools patches Geoff Levand
2016-07-19 23:28 ` Geoff Levand
2016-07-19 23:28 ` [PATCH v1 4/4] arm64: Add support for binary image files Geoff Levand
2016-07-19 23:28   ` Geoff Levand
2016-07-19 23:28 ` [PATCH v1 3/4] arm64: Add arm64 kexec support Geoff Levand
2016-07-19 23:28   ` Geoff Levand
2016-07-20 15:39   ` Mark Rutland
2016-07-20 15:39     ` Mark Rutland
2016-07-20 19:19     ` Geoff Levand
2016-07-20 19:19       ` Geoff Levand
2016-07-21 10:31       ` Mark Rutland
2016-07-21 10:31         ` Mark Rutland
2016-07-21 10:50         ` Robin Murphy [this message]
2016-07-21 10:50           ` Robin Murphy
2016-07-21 21:49           ` Geoff Levand
2016-07-21 21:49             ` Geoff Levand
2016-07-22  4:08             ` Pratyush Anand
2016-07-22  4:08               ` Pratyush Anand
2016-07-22  5:33               ` AKASHI Takahiro
2016-07-22  5:33                 ` AKASHI Takahiro
2016-07-22  9:54               ` Mark Rutland
2016-07-22  9:54                 ` Mark Rutland
2016-07-22 10:03               ` Robin Murphy
2016-07-22 10:03                 ` Robin Murphy
2016-07-22 13:56                 ` Pratyush Anand
2016-07-22 13:56                   ` Pratyush Anand
2016-07-22 17:59                   ` Robin Murphy
2016-07-22 17:59                     ` Robin Murphy
2016-07-25 21:56                 ` Geoff Levand
2016-07-25 21:56                   ` Geoff Levand
2016-07-20 17:53   ` Pratyush Anand
2016-07-20 17:53     ` Pratyush Anand
2016-07-20 20:33     ` Geoff Levand
2016-07-20 20:33       ` Geoff Levand
2016-07-20 20:54   ` [PATCH v1.2 " Geoff Levand
2016-07-20 20:54     ` Geoff Levand
2016-07-22  7:12     ` AKASHI Takahiro
2016-07-22  7:12       ` AKASHI Takahiro
2016-07-26  0:37       ` Geoff Levand
2016-07-26  0:37         ` Geoff Levand
2016-07-25 14:28     ` Ruslan Bilovol
2016-07-25 14:28       ` Ruslan Bilovol
2016-07-25 20:50       ` Geoff Levand
2016-07-25 20:50         ` Geoff Levand
2016-07-26  1:36         ` Ruslan Bilovol
2016-07-26  1:36           ` Ruslan Bilovol
2016-07-26  8:16           ` AKASHI Takahiro
2016-07-26  8:16             ` AKASHI Takahiro
2016-07-26 21:26             ` Ruslan Bilovol
2016-07-26 21:26               ` Ruslan Bilovol
2016-07-26 21:54               ` Geoff Levand
2016-07-26 21:54                 ` Geoff Levand
2016-07-19 23:28 ` [PATCH v1 1/4] kexec: (bugfix) calc correct end address of memory ranges in device tree Geoff Levand
2016-07-19 23:28   ` Geoff Levand
2016-07-27 22:45   ` Thiago Jung Bauermann
2016-07-27 22:45     ` Thiago Jung Bauermann
2016-07-27 23:23     ` Russell King - ARM Linux
2016-07-27 23:23       ` Russell King - ARM Linux
2016-07-28 23:54       ` Thiago Jung Bauermann
2016-07-28 23:54         ` Thiago Jung Bauermann
2016-07-29  8:27         ` Russell King - ARM Linux
2016-07-29  8:27           ` Russell King - ARM Linux
2016-07-29 17:12           ` Geoff Levand
2016-07-29 17:12             ` Geoff Levand
2016-07-29 17:23             ` Russell King - ARM Linux
2016-07-29 17:23               ` Russell King - ARM Linux
2016-08-01  4:52               ` AKASHI Takahiro
2016-08-01  4:52                 ` AKASHI Takahiro
2016-09-06  0:29                 ` Memory range end be inclusive or exclusive? " AKASHI Takahiro
2016-09-06  0:29                   ` AKASHI Takahiro
2016-10-31  8:50                   ` AKASHI Takahiro
2016-10-31  8:50                     ` AKASHI Takahiro
2016-11-07  8:17                     ` Simon Horman
2016-11-07  8:17                       ` Simon Horman
2016-07-19 23:28 ` [PATCH v1 2/4] kexec: Add common device tree routines Geoff Levand
2016-07-19 23:28   ` Geoff Levand
2016-07-22  7:19   ` AKASHI Takahiro
2016-07-22  7:19     ` AKASHI Takahiro
2016-07-27 18:11     ` Geoff Levand
2016-07-27 18:11       ` Geoff Levand
2016-07-20  4:30 ` [PATCH v1 0/4] arm64 kexec-tools patches AKASHI Takahiro
2016-07-20  4:30   ` AKASHI Takahiro
2016-07-26 23:05 ` Simon Horman
2016-07-26 23:05   ` Simon Horman
2016-07-27  5:57   ` AKASHI Takahiro
2016-07-27  5:57     ` AKASHI Takahiro
2016-07-28 18:09   ` Geoff Levand
2016-07-28 18:09     ` Geoff Levand
2016-07-29  0:31     ` Simon Horman
2016-07-29  0:31       ` Simon Horman

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