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[82.11.51.62]) by smtp.gmail.com with ESMTPSA id a20-20020a1709064a5400b00992b50fbbe9sm3285195ejv.90.2023.08.27.03.31.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 27 Aug 2023 03:31:36 -0700 (PDT) Message-ID: <8d2ba0d3-55eb-45cf-b88a-bafef35e96b9@linux.com> Date: Sun, 27 Aug 2023 11:31:35 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] Revert "tty: serial: meson: Add a earlycon for the T7 SoC" Content-Language: en-US To: Neil Armstrong , Greg Kroah-Hartman , Jiri Slaby , Kevin Hilman Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org References: <20230827082944.5100-1-tanure@linux.com> <7bf9e716-0ff2-56d5-07ab-db027901454e@linaro.org> <09735262-1bc0-40cf-b139-22cccf70bcab@linux.com> From: Lucas Tanure In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27-08-2023 11:23, Neil Armstrong wrote: > Hi Lucas, > > Le 27/08/2023 à 12:04, Lucas Tanure a écrit : >> On 27-08-2023 10:48, Neil Armstrong wrote: >>> Hi Lucas, >>> >>> Le 27/08/2023 à 10:29, Lucas Tanure a écrit : >>>> This reverts commit 6a4197f9763325043abf7690a21124a9facbf52e. >>>> New SoC will use ttyS0 instead of ttyAML, so T7 SoC doesn't need a >>>> OF_EARLYCON_DECLARE. >>>> >>>> Signed-off-by: Lucas Tanure >>>> --- >>>> Since V1: >>>> - add Signed-off-by: >>>> >>>>   drivers/tty/serial/meson_uart.c | 2 -- >>>>   1 file changed, 2 deletions(-) >>>> >>>> diff --git a/drivers/tty/serial/meson_uart.c >>>> b/drivers/tty/serial/meson_uart.c >>>> index c4f61d82fb727..790d910dafa5d 100644 >>>> --- a/drivers/tty/serial/meson_uart.c >>>> +++ b/drivers/tty/serial/meson_uart.c >>>> @@ -648,8 +648,6 @@ meson_serial_early_console_setup(struct >>>> earlycon_device *device, const char *opt >>>>   OF_EARLYCON_DECLARE(meson, "amlogic,meson-ao-uart", >>>>               meson_serial_early_console_setup); >>>> -OF_EARLYCON_DECLARE(meson, "amlogic,t7-uart", >>>> -            meson_serial_early_console_setup); >>>>   #define MESON_SERIAL_CONSOLE_PTR(_devname) >>>> (&meson_serial_console_##_devname) >>>>   #else >>> >>> How do you use earlycon with this removed ? >>> >>> Neil >> This is my kernel cmdline: >> console=ttyS0,921600 no_console_suspend earlycon=ttyS0,0xfe078000 >> >> And I can see my log: >> boot 64bit kernel >> [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x410fd092] >> [    0.000000] Linux version 6.5.0-rc7-next-20230825+ (tanureal@ryzen) >> (aarch64-none-linux-gnu-gcc (GNU Toolchain for the A-profile >> Architecture 10.3-2021.07 (arm-10.29)) 10.3.1 20210621, GNU ld (GNU >> Toolchain fo3 >> [    0.000000] KASLR disabled due to lack of seed >> [    0.000000] Machine model: Khadas vim4 >> [    0.000000] OF: reserved mem: >> 0x0000000005000000..0x00000000052fffff (3072 KiB) nomap non-reusable >> secmon@5000000 >> [    0.000000] OF: reserved mem: >> 0x0000000005300000..0x00000000072fffff (32768 KiB) nomap non-reusable >> secmon@5300000 >> ... >> [    0.079368] io scheduler mq-deadline registered >> [    0.079374] io scheduler kyber registered >> [    0.079549] io scheduler bfq registered >> [    0.083373] fe078000.serial: ttyS0 at MMIO 0xfe078000 (irq = 14, >> base_baud = 1500000) is a meson_uart >> [    0.083403] printk: console [ttyS0] enabled >> >> As the log is OK, and T7 for now is binding against S4 code we should >> drop this patch and add a S4 one if needed. >> >> But just having this log is not enough for testing earlycon? >> I am assuming that by just having the log since 0.0000 is a good sign >> that earlycon is working. >> Could you give further guidance? > > First the kernel argument is simply "earlycon" with no other options, > the earlycon code will fetch the first uart using the DT > /chosen/stdout-path property. > > Then you should see something like right after "Machine model": > [    0.000000] earlycon: meson0 at MMIO 0x00000000ff803000 (options > '115200n8') > > The boot log you share doesn't use earlycon, it waits until all > depedency of the UART > has been probed before probing the UART driver and prints the whole boot > log. > > Earlycon is a mechanism to use the UART HW as configured by the > bootloader in > a minimal way very early in the boot in order to detect very early lockups. > > Keeping OF_EARLYCON_DECLARE for t7 would enable this. > > Neil > >> >> Lucas Tanure >> > But then we would need to add Earlycon for S4 too. How can we add one Earlycon for all future SoCs, like S4 and T7?