From: Scott Branden <scott.branden@broadcom.com>
To: Florian Fainelli <f.fainelli@gmail.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Olof Johansson <olof@lixom.net>
Cc: Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org,
bcm-kernel-feedback-list@broadcom.com
Subject: Re: [PATCH v5 15/15] misc: bcm-vk: add ttyVK support
Date: Thu, 1 Oct 2020 15:26:41 -0700 [thread overview]
Message-ID: <140a5cde-67fd-f4b1-e4a9-9c68adf964c4@broadcom.com> (raw)
In-Reply-To: <278afb05-8c8d-98d2-eed0-f73b954b03c7@gmail.com>
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Hi Florian,
On 2020-09-30 7:36 p.m., Florian Fainelli wrote:
>
>
> On 9/30/2020 6:28 PM, Scott Branden wrote:
>> Add ttyVK support to driver to allow console access to VK card from host.
>>
>> Device node will be in the follow form /dev/bcm-vk.x_ttyVKy where:
>> x is the instance of the VK card
>> y is the tty device number on the VK card
>>
>> Signed-off-by: Scott Branden <scott.branden@broadcom.com>
>
> Was it not possible to:
>
> - emulate a standard 8250 UART and just expose an additional bar + MSI vector such that one could get a debug UART out of this device with little to no work on the host side?
I don't see how such emulation is simpler than what we have. For a standard 8250 UART implementation how would we emulate a FIFO in memory accessible over PCIe. I don't see how to do that with shared memory? Also, we don't have an additional bar available on the PCIe device. There is currently little to no work on the device side using a circular buffer with read and write pointers.
>
> - or use virtio console and implement virtio on the firmware that runs on VK?
Not that possible as the debug/console UARTs are used inside and outside of linux on the VK card.
>
> It's not a lot of code, but it just feels like this should not have to be done at all.
If there was a simpler way to do it, yes, I would like a "UART" running over PCIe shared memory via a circular buffer.
And that is what the code we developed does.
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next prev parent reply other threads:[~2020-10-01 22:26 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 1:27 [PATCH v5 00/15] Add Broadcom VK driver Scott Branden
2020-10-01 1:27 ` [PATCH v5 01/15] bcm-vk: add bcm_vk UAPI Scott Branden
2020-10-01 1:27 ` [PATCH v5 02/15] misc: bcm-vk: add Broadcom VK driver Scott Branden
2020-10-01 1:27 ` [PATCH v5 03/15] misc: bcm-vk: add autoload support Scott Branden
2020-10-01 4:07 ` kernel test robot
2020-10-01 17:48 ` Scott Branden
2020-10-02 5:36 ` [kbuild-all] " Philip Li
2020-10-01 1:27 ` [PATCH v5 04/15] misc: bcm-vk: add misc device to Broadcom VK driver Scott Branden
2020-10-01 1:28 ` [PATCH v5 05/15] misc: bcm-vk: add triggers when host panic or reboots to notify card Scott Branden
2020-10-01 1:28 ` [PATCH v5 06/15] misc: bcm-vk: add open/release Scott Branden
2020-10-01 1:28 ` [PATCH v5 07/15] misc: bcm-vk: add ioctl load_image Scott Branden
2020-10-01 1:28 ` [PATCH v5 08/15] misc: bcm-vk: add get_card_info, peerlog_info, and proc_mon_info Scott Branden
2020-10-01 1:28 ` [PATCH v5 09/15] misc: bcm-vk: add VK messaging support Scott Branden
2020-10-01 1:43 ` Joe Perches
2020-10-01 18:27 ` Scott Branden
2020-10-01 1:28 ` [PATCH v5 10/15] misc: bcm-vk: reset_pid support Scott Branden
2020-10-01 1:28 ` [PATCH v5 11/15] misc: bcm-vk: add BCM_VK_QSTATS Scott Branden
2020-10-01 2:33 ` Florian Fainelli
2020-10-01 22:12 ` Scott Branden
2020-10-01 22:13 ` Florian Fainelli
2020-10-02 16:54 ` Scott Branden
2020-10-02 4:55 ` Greg Kroah-Hartman
2020-10-02 16:52 ` Scott Branden
2020-10-01 1:28 ` [PATCH v5 12/15] misc: bcm-vk: add sysfs interface Scott Branden
2020-10-01 2:30 ` Florian Fainelli
2020-10-01 22:17 ` Scott Branden
2020-10-01 1:28 ` [PATCH v5 13/15] misc: bcm-vk: add mmap function for exposing BAR2 Scott Branden
2020-10-01 1:28 ` [PATCH v5 14/15] MAINTAINERS: bcm-vk: add maintainer for Broadcom VK Driver Scott Branden
2020-10-01 1:28 ` [PATCH v5 15/15] misc: bcm-vk: add ttyVK support Scott Branden
2020-10-01 2:36 ` Florian Fainelli
2020-10-01 22:26 ` Scott Branden [this message]
2020-10-01 2:38 ` [PATCH v5 00/15] Add Broadcom VK driver Florian Fainelli
2020-10-01 12:24 ` Olof Johansson
2020-10-01 22:34 ` Scott Branden
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