linux-kernel - Re: [PATCH] serial: core: Use cons->index for preferred console registration

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Message-ID: <7284590f-2b74-1b47-2d61-783ad8d5f46f@monstr.eu>
Date:   Tue, 15 Oct 2019 11:22:28 +0200
From:   Michal Simek <monstr@...str.eu>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <michal.simek@...inx.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Jiri Slaby <jslaby@...e.com>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH] serial: core: Use cons->index for preferred console
 registration

Hi Geert,

On 15. 10. 19 11:19, Geert Uytterhoeven wrote:
> Hi Michal,
> 
> On Mon, Sep 2, 2019 at 4:29 PM Michal Simek <michal.simek@...inx.com> wrote:
>> The reason for this patch is xilinx_uartps driver which create one dynamic
>> instance per IP with unique major and minor combinations. drv->nr is in
>> this case all the time setup to 1. That means that uport->line is all the
>> time setup to 0 and drv->tty_driver->name_base is doing shift in name to
>> for example ttyPS3.
>>
>> register_console() is looping over console_cmdline array and looking for
>> proper name/index combination which is in our case ttyPS/3.
>> That's why every instance of driver needs to be registered with proper
>> combination of name/number (ttyPS/3). Using uport->line is doing
>> registration with ttyPS/0 which is wrong that's why proper console index
>> should be used which is in cons->index field.
>>
>> Also it is visible that recording console should be done based on
>> information about console not about the port but in most cases numbers are
>> the same and xilinx_uartps is only one exception now.
>>
>> Signed-off-by: Michal Simek <michal.simek@...inx.com>
> 
> This is now commit 91daae03188e0dd1 ("serial: core: Use cons->index
> for preferred console registration") in tty-next.
> 
> This has been bisected to break the serial console on (at least)
> r8a7791/koelsch and r8a7795/h3-salvator-xs.
> 
> The line "printk: console [ttySC0] enabled" is no longer printed.
> The system continues booting without any serial console output, and the
> login prompt never appears on the serial console.
> 
> Reverting this commit fixes the issue.

Sorry for trouble with this patch. Can you please point me to dts files
for these boards and also what's the value you have in uport->line and
uport->cons->index?

Thanks,
Michal


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP/Versal SoCs