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: Fri, 22 Jul 2016 11:03:14 +0100 [thread overview]
Message-ID: <5791EF62.5070006@arm.com> (raw)
In-Reply-To: <20160722040842.GA14911@localhost.localdomain>
On 22/07/16 05:08, Pratyush Anand wrote:
> On 21/07/2016:02:49:36 PM, Geoff Levand wrote:
>> On Thu, 2016-07-21 at 11:50 +0100, Robin Murphy wrote:
>>> 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.
>>
>> Here's what I came up with.
>>
>>
>> + struct data {const char *name; int tx_offset;};
>> + static const struct data ok_list[] = {
>> + /* {"armada-3700-uart", ?}, */
>> + {"exynos4210-uart", 0x20},
>> + /* {"ls1021a-lpuart", ?}, */
>> + /* {"meson-uart", ?}, */
>> + /* {"mt6577-uart", ?}, */
>> + {"ns16550", 0},
>> + {"ns16550a", 0},
>> + {"pl011", 0},
>> + {NULL, 0}
>> + };
>
> sinc functionality is just to debug the scenario when something goes wrong in
> purgatory. IMHO, it should be disabled by default. So, why not to keep it as
> simple as possible. Its a low level debugging mainly for developer, so user
> should know the absolute address. Therefore, I think no need to parse earlycon
> or earlyprintk from command line. Whatever user passes in --port can be treated
> as address of TX register. If TX offset is 0x20, then user can pass --port as
> base+0x20. Additionally, we can pass TX register width as well. So what about
> something like "--port=0x1c020000,1" where 0x1c020000 is TX register address and
> 1 says about it's width in bytes.
I don't think even that is worthwhile, since without any polling it
still relies on the UART having FIFOs, someone having already enabled
the FIFOs, the FIFOs being deep enough and/or the output being short
enough. In short, it's fragile enough that I'm not convinced it's even
useful as a debug option. I suggest we simply copy the purgatory console
implementation from, say, ARM or Alpha.
Robin.
>
> ~Pratyush
>
next prev parent reply other threads:[~2016-07-22 10:03 UTC|newest]
Thread overview: 45+ 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 ` [PATCH v1 1/4] kexec: (bugfix) calc correct end address of memory ranges in device tree Geoff Levand
2016-07-27 22:45 ` Thiago Jung Bauermann
2016-07-27 23:23 ` Russell King - ARM Linux
2016-07-28 23:54 ` Thiago Jung Bauermann
2016-07-29 8:27 ` Russell King - ARM Linux
2016-07-29 17:12 ` Geoff Levand
2016-07-29 17:23 ` Russell King - ARM Linux
2016-08-01 4:52 ` AKASHI Takahiro
2016-09-06 0:29 ` Memory range end be inclusive or exclusive? " AKASHI Takahiro
2016-10-31 8:50 ` AKASHI Takahiro
2016-11-07 8:17 ` Simon Horman
2016-07-19 23:28 ` [PATCH v1 2/4] kexec: Add common device tree routines Geoff Levand
2016-07-22 7:19 ` AKASHI Takahiro
2016-07-27 18:11 ` 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 ` [PATCH v1 3/4] arm64: Add arm64 kexec support Geoff Levand
2016-07-20 15:39 ` Mark Rutland
2016-07-20 19:19 ` Geoff Levand
2016-07-21 10:31 ` Mark Rutland
2016-07-21 10:50 ` Robin Murphy
2016-07-21 21:49 ` Geoff Levand
2016-07-22 4:08 ` Pratyush Anand
2016-07-22 5:33 ` AKASHI Takahiro
2016-07-22 9:54 ` Mark Rutland
2016-07-22 10:03 ` Robin Murphy [this message]
2016-07-22 13:56 ` Pratyush Anand
2016-07-22 17:59 ` Robin Murphy
2016-07-25 21:56 ` Geoff Levand
2016-07-20 17:53 ` Pratyush Anand
2016-07-20 20:33 ` Geoff Levand
2016-07-20 20:54 ` [PATCH v1.2 " Geoff Levand
2016-07-22 7:12 ` AKASHI Takahiro
2016-07-26 0:37 ` Geoff Levand
2016-07-25 14:28 ` Ruslan Bilovol
2016-07-25 20:50 ` Geoff Levand
2016-07-26 1:36 ` Ruslan Bilovol
2016-07-26 8:16 ` AKASHI Takahiro
2016-07-26 21:26 ` Ruslan Bilovol
2016-07-26 21:54 ` Geoff Levand
2016-07-20 4:30 ` [PATCH v1 0/4] arm64 kexec-tools patches AKASHI Takahiro
2016-07-26 23:05 ` Simon Horman
2016-07-27 5:57 ` AKASHI Takahiro
2016-07-28 18:09 ` Geoff Levand
2016-07-29 0:31 ` Simon Horman
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