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([2a01:e0a:982:cbb0:535e:33c9:c7dd:4940]) by smtp.gmail.com with ESMTPSA id bw14-20020a0560001f8e00b0032d886039easm6912044wrb.14.2023.10.13.08.37.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Oct 2023 08:37:07 -0700 (PDT) Message-ID: <5765a10c-8f75-4bf4-830b-b5fba501d164@linaro.org> Date: Fri, 13 Oct 2023 17:37:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Reply-To: neil.armstrong@linaro.org Subject: Re: [PATCH v4] tty: serial: meson: fix hard LOCKUP on crtscts mode Content-Language: en-US, fr To: Dmitry Rokosov , Pavel Krasavin Cc: Greg Kroah-Hartman , Jiri Slaby , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org References: <20231013141818.adq6eujrx2wueobp@CAB-WSD-L081021> Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro Developer Services In-Reply-To: <20231013141818.adq6eujrx2wueobp@CAB-WSD-L081021> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/10/2023 16:18, Dmitry Rokosov wrote: > I believe it would be necessary to include a 'Fixes' tag for that. Neil, > what do you think? > Since a HARDLOCKUP is an undesirable situation, I don't think we want to > have it in the LTS kernels either. Yes, and please keep the previous Reviewed-by Dmitry and I added on v3 and send a v5 with the Fixes added. It should be: Fixes: ff7693d079e5 ("ARM: meson: serial: add MesonX SoC on-chip uart driver") Hopefully it will be the last iteration. Thanks, Neil > > On Fri, Oct 13, 2023 at 11:48:39AM +0000, Pavel Krasavin wrote: >> From: Pavel Krasavin >> >> There might be hard lockup if we set crtscts mode on port without RTS/CTS configured: >> >> # stty -F /dev/ttyAML6 crtscts; echo 1 > /dev/ttyAML6; echo 2 > /dev/ttyAML6 >> [ 95.890386] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: >> [ 95.890857] rcu: 3-...0: (201 ticks this GP) idle=e33c/1/0x4000000000000000 softirq=5844/5846 fqs=4984 >> [ 95.900212] rcu: (detected by 2, t=21016 jiffies, g=7753, q=296 ncpus=4) >> [ 95.906972] Task dump for CPU 3: >> [ 95.910178] task:bash state:R running task stack:0 pid:205 ppid:1 flags:0x00000202 >> [ 95.920059] Call trace: >> [ 95.922485] __switch_to+0xe4/0x168 >> [ 95.925951] 0xffffff8003477508 >> [ 95.974379] watchdog: Watchdog detected hard LOCKUP on cpu 3 >> [ 95.974424] Modules linked in: 88x2cs(O) rtc_meson_vrtc >> >> Possible solution would be to not allow to setup crtscts on such port. >> >> Tested on S905X3 based board. >> >> Signed-off-by: Pavel Krasavin >> --- >> v4: More correct patch subject according to Jiri's note >> v3: https://lore.kernel.org/lkml/OF6CF5FFA0.CCFD0E8E-ON00258A46.00549EDF-00258A46.0054BB62@gdc.ru/ >> "From:" line added to the mail >> v2: https://lore.kernel.org/lkml/OF950BEF72.7F425944-ON00258A46.00488A76-00258A46.00497D44@gdc.ru/ >> braces for single statement removed according to Dmitry's note >> v1: https://lore.kernel.org/lkml/OF28B2B8C9.5BC0CD28-ON00258A46.0037688F-00258A46.0039155B@gdc.ru/ >> --- >> >> --- a/drivers/tty/serial/meson_uart.c 2023-10-12 15:44:02.410538523 +0300 >> +++ b/drivers/tty/serial/meson_uart.c 2023-10-12 15:58:06.242395253 +0300 >> @@ -380,10 +380,14 @@ static void meson_uart_set_termios(struc >> else >> val |= AML_UART_STOP_BIT_1SB; >> >> - if (cflags & CRTSCTS) >> - val &= ~AML_UART_TWO_WIRE_EN; >> - else >> + if (cflags & CRTSCTS) { >> + if (port->flags & UPF_HARD_FLOW) >> + val &= ~AML_UART_TWO_WIRE_EN; >> + else >> + termios->c_cflag &= ~CRTSCTS; >> + } else { >> val |= AML_UART_TWO_WIRE_EN; >> + } >> >> writel(val, port->membase + AML_UART_CONTROL); >> >> @@ -705,6 +709,7 @@ static int meson_uart_probe(struct platf >> u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */ >> int ret = 0; >> int irq; >> + bool has_rtscts; >> >> if (pdev->dev.of_node) >> pdev->id = of_alias_get_id(pdev->dev.of_node, "serial"); >> @@ -732,6 +737,7 @@ static int meson_uart_probe(struct platf >> return irq; >> >> of_property_read_u32(pdev->dev.of_node, "fifo-size", &fifosize); >> + has_rtscts = of_property_read_bool(pdev->dev.of_node, "uart-has-rtscts"); >> >> if (meson_ports[pdev->id]) { >> return dev_err_probe(&pdev->dev, -EBUSY, >> @@ -762,6 +768,8 @@ static int meson_uart_probe(struct platf >> port->mapsize = resource_size(res_mem); >> port->irq = irq; >> port->flags = UPF_BOOT_AUTOCONF | UPF_LOW_LATENCY; >> + if (has_rtscts) >> + port->flags |= UPF_HARD_FLOW; >> port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_MESON_CONSOLE); >> port->dev = &pdev->dev; >> port->line = pdev->id; >> >> _______________________________________________ >> linux-amlogic mailing list >> linux-amlogic@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-amlogic >