From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9A2053398E; Wed, 30 Oct 2024 06:06:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730268363; cv=none; b=RdlobnJ6seCUUPMEsQVQ5D4cCrJFRK5tecHXY1km8c+qQbrWPJZd1/TLyC7Lj+obHSCkjoyipZFMgSU249uuhT6CL0DShPhQVCDHi/C0bBKt12JqzRf0oZamJ2Ox6zppvIHpDl8VCE6wJYuBEA8CYfNC6Gf4ANjuSTtrd6ECykY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730268363; c=relaxed/simple; bh=0rd+rGQmI4YEvdffyJPpjxLIs/ZAPUeX/9lNkFELPPM=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZRODSJjeY6k0iAYt41df0MJR3GwtEv8y1QZwjwb9OmSrML1u8pTujWiw+A/Vn94Mk+L76dh/k9MtJzHWvzapKKv3vSS7i/2Je63kinR6dmN35xup8P0YDuzT7mI/n7prWtrGBhVSvT1TjWldVnY1D33zScmSSO3vM67X2URWGY8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=bO9/H4td; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="bO9/H4td" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7535AC4CEE4; Wed, 30 Oct 2024 06:06:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730268363; bh=0rd+rGQmI4YEvdffyJPpjxLIs/ZAPUeX/9lNkFELPPM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=bO9/H4tdpBg8nxHwsrHKPQS3Y+khT2DDEZ3GvkZy0+VvRQ+XBqDrwO27YaM+eXCWz DBhD7cQdN2upZ2fwbVY6N//mLJaBnmIQE7cuDayhU+ipoU0CaSkQp1nNanZ9v6ce6o 0leqYP0v06lNySGkGcI4kDQOIaiRXAw1DR6O1Q5+s3gXX5HFd0PbvGqopnsirBsst4 Jpis2QTianN/WJ5gR3VN5h+c8Pf3akOxRXMpn55fmv74x+6DQjhtMBsQfjiFxSzGrh wIYBvLm6BQr4oIPtz5O6sIFaG+dgV0xk1qaeZ9MbxLL6Ye85FH8RB1TnxWrya/lGl8 IgArXtwDP+pYQ== Message-ID: <837a7ecd-be29-4865-9543-cb6f7e7e46e7@kernel.org> Date: Wed, 30 Oct 2024 07:05:58 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH tty-next v3 1/6] serial: 8250: Adjust the timeout for FIFO mode To: John Ogness , Greg Kroah-Hartman Cc: Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , Esben Haabendal , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Shevchenko , Rengarajan S , Jeff Johnson , Serge Semin , Lino Sanfilippo , Wander Lairson Costa References: <20241025105728.602310-1-john.ogness@linutronix.de> <20241025105728.602310-2-john.ogness@linutronix.de> Content-Language: en-US From: Jiri Slaby Autocrypt: addr=jirislaby@kernel.org; keydata= xsFNBE6S54YBEACzzjLwDUbU5elY4GTg/NdotjA0jyyJtYI86wdKraekbNE0bC4zV+ryvH4j rrcDwGs6tFVrAHvdHeIdI07s1iIx5R/ndcHwt4fvI8CL5PzPmn5J+h0WERR5rFprRh6axhOk rSD5CwQl19fm4AJCS6A9GJtOoiLpWn2/IbogPc71jQVrupZYYx51rAaHZ0D2KYK/uhfc6neJ i0WqPlbtIlIrpvWxckucNu6ZwXjFY0f3qIRg3Vqh5QxPkojGsq9tXVFVLEkSVz6FoqCHrUTx wr+aw6qqQVgvT/McQtsI0S66uIkQjzPUrgAEtWUv76rM4ekqL9stHyvTGw0Fjsualwb0Gwdx ReTZzMgheAyoy/umIOKrSEpWouVoBt5FFSZUyjuDdlPPYyPav+hpI6ggmCTld3u2hyiHji2H cDpcLM2LMhlHBipu80s9anNeZhCANDhbC5E+NZmuwgzHBcan8WC7xsPXPaiZSIm7TKaVoOcL 9tE5aN3jQmIlrT7ZUX52Ff/hSdx/JKDP3YMNtt4B0cH6ejIjtqTd+Ge8sSttsnNM0CQUkXps w98jwz+Lxw/bKMr3NSnnFpUZaxwji3BC9vYyxKMAwNelBCHEgS/OAa3EJoTfuYOK6wT6nadm YqYjwYbZE5V/SwzMbpWu7Jwlvuwyfo5mh7w5iMfnZE+vHFwp/wARAQABzSFKaXJpIFNsYWJ5 IDxqaXJpc2xhYnlAa2VybmVsLm9yZz7CwXcEEwEIACEFAlW3RUwCGwMFCwkIBwIGFQgJCgsC BBYCAwECHgECF4AACgkQvSWxBAa0cEnVTg//TQpdIAr8Tn0VAeUjdVIH9XCFw+cPSU+zMSCH eCZoA/N6gitEcnvHoFVVM7b3hK2HgoFUNbmYC0RdcSc80pOF5gCnACSP9XWHGWzeKCARRcQR 4s5YD8I4VV5hqXcKo2DFAtIOVbHDW+0okOzcecdasCakUTr7s2fXz97uuoc2gIBB7bmHUGAH XQXHvdnCLjDjR+eJN+zrtbqZKYSfj89s/ZHn5Slug6w8qOPT1sVNGG+eWPlc5s7XYhT9z66E l5C0rG35JE4PhC+tl7BaE5IwjJlBMHf/cMJxNHAYoQ1hWQCKOfMDQ6bsEr++kGUCbHkrEFwD UVA72iLnnnlZCMevwE4hc0zVhseWhPc/KMYObU1sDGqaCesRLkE3tiE7X2cikmj/qH0CoMWe gjnwnQ2qVJcaPSzJ4QITvchEQ+tbuVAyvn9H+9MkdT7b7b2OaqYsUP8rn/2k1Td5zknUz7iF oJ0Z9wPTl6tDfF8phaMIPISYrhceVOIoL+rWfaikhBulZTIT5ihieY9nQOw6vhOfWkYvv0Dl o4GRnb2ybPQpfEs7WtetOsUgiUbfljTgILFw3CsPW8JESOGQc0Pv8ieznIighqPPFz9g+zSu Ss/rpcsqag5n9rQp/H3WW5zKUpeYcKGaPDp/vSUovMcjp8USIhzBBrmI7UWAtuedG9prjqfO wU0ETpLnhgEQAM+cDWLL+Wvc9cLhA2OXZ/gMmu7NbYKjfth1UyOuBd5emIO+d4RfFM02XFTI t4MxwhAryhsKQQcA4iQNldkbyeviYrPKWjLTjRXT5cD2lpWzr+Jx7mX7InV5JOz1Qq+P+nJW YIBjUKhI03ux89p58CYil24Zpyn2F5cX7U+inY8lJIBwLPBnc9Z0An/DVnUOD+0wIcYVnZAK DiIXODkGqTg3fhZwbbi+KAhtHPFM2fGw2VTUf62IHzV+eBSnamzPOBc1XsJYKRo3FHNeLuS8 f4wUe7bWb9O66PPFK/RkeqNX6akkFBf9VfrZ1rTEKAyJ2uqf1EI1olYnENk4+00IBa+BavGQ 8UW9dGW3nbPrfuOV5UUvbnsSQwj67pSdrBQqilr5N/5H9z7VCDQ0dhuJNtvDSlTf2iUFBqgk 3smln31PUYiVPrMP0V4ja0i9qtO/TB01rTfTyXTRtqz53qO5dGsYiliJO5aUmh8swVpotgK4 /57h3zGsaXO9PGgnnAdqeKVITaFTLY1ISg+Ptb4KoliiOjrBMmQUSJVtkUXMrCMCeuPDGHo7 39Xc75lcHlGuM3yEB//htKjyprbLeLf1y4xPyTeeF5zg/0ztRZNKZicgEmxyUNBHHnBKHQxz 1j+mzH0HjZZtXjGu2KLJ18G07q0fpz2ZPk2D53Ww39VNI/J9ABEBAAHCwV8EGAECAAkFAk6S 54YCGwwACgkQvSWxBAa0cEk3tRAAgO+DFpbyIa4RlnfpcW17AfnpZi9VR5+zr496n2jH/1ld wRO/S+QNSA8qdABqMb9WI4BNaoANgcg0AS429Mq0taaWKkAjkkGAT7mD1Q5PiLr06Y/+Kzdr 90eUVneqM2TUQQbK+Kh7JwmGVrRGNqQrDk+gRNvKnGwFNeTkTKtJ0P8jYd7P1gZb9Fwj9YLx jhn/sVIhNmEBLBoI7PL+9fbILqJPHgAwW35rpnq4f/EYTykbk1sa13Tav6btJ+4QOgbcezWI wZ5w/JVfEJW9JXp3BFAVzRQ5nVrrLDAJZ8Y5ioWcm99JtSIIxXxt9FJaGc1Bgsi5K/+dyTKL wLMJgiBzbVx8G+fCJJ9YtlNOPWhbKPlrQ8+AY52Aagi9WNhe6XfJdh5g6ptiOILm330mkR4g W6nEgZVyIyTq3ekOuruftWL99qpP5zi+eNrMmLRQx9iecDNgFr342R9bTDlb1TLuRb+/tJ98 f/bIWIr0cqQmqQ33FgRhrG1+Xml6UXyJ2jExmlO8JljuOGeXYh6ZkIEyzqzffzBLXZCujlYQ DFXpyMNVJ2ZwPmX2mWEoYuaBU0JN7wM+/zWgOf2zRwhEuD3A2cO2PxoiIfyUEfB9SSmffaK/ S4xXoB6wvGENZ85Hg37C7WDNdaAt6Xh2uQIly5grkgvWppkNy4ZHxE+jeNsU7tg= In-Reply-To: <20241025105728.602310-2-john.ogness@linutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 25. 10. 24, 12:57, John Ogness wrote: > After a console has fed a line into TX, it uses wait_for_xmitr() > to wait until the data has been sent out before returning to the > printk code. However, wait_for_xmitr() will timeout after 10ms, > regardless if the data has been transmitted or not. > > For single bytes, this timeout is sufficient even at very slow > baud rates, such as 1200bps. However, when FIFO mode is used, > there may be 64 bytes pushed into the FIFO at once. At a baud > rate of 115200bps, the 10ms timeout is still sufficient. > However, when using lower baud rates (such as 57600bps), the > timeout is _not_ sufficient. This causes longer lines to be cut > off, resulting in lost and horribly misformatted output on the > console. > > When using FIFO mode, take the number of bytes into account to > determine an appropriate max timeout. Increasing the timeout > does not affect performance since ideally the timeout never > occurs. > > Fixes: 8f3631f0f6eb ("serial/8250: Use fifo in 8250 console driver") > Signed-off-by: John Ogness > --- > drivers/tty/serial/8250/8250_port.c | 24 ++++++++++++++++++++---- > 1 file changed, 20 insertions(+), 4 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c > index 3509af7dc52b..adc48eeeac2b 100644 > --- a/drivers/tty/serial/8250/8250_port.c > +++ b/drivers/tty/serial/8250/8250_port.c > @@ -2059,11 +2059,12 @@ static void serial8250_break_ctl(struct uart_port *port, int break_state) > serial8250_rpm_put(up); > } > > -static void wait_for_lsr(struct uart_8250_port *up, int bits) > +/* Returns true if @bits were set, false on timeout. */ > +static bool wait_for_lsr(struct uart_8250_port *up, int bits) > { > unsigned int status, tmout = 10000; > > - /* Wait up to 10ms for the character(s) to be sent. */ > + /* Wait up to 10ms for the character to be sent. */ > for (;;) { > status = serial_lsr_in(up); > > @@ -2074,10 +2075,13 @@ static void wait_for_lsr(struct uart_8250_port *up, int bits) > udelay(1); > touch_nmi_watchdog(); > } > + > + return (tmout != 0); > } > > /* > * Wait for transmitter & holding register to empty > + * with timeout > */ > static void wait_for_xmitr(struct uart_8250_port *up, int bits) > { > @@ -3306,13 +3310,18 @@ static void serial8250_console_restore(struct uart_8250_port *up) > static void serial8250_console_fifo_write(struct uart_8250_port *up, > const char *s, unsigned int count) > { > - int i; > const char *end = s + count; > unsigned int fifosize = up->tx_loadsz; > + unsigned int tx_count = 0; > bool cr_sent = false; > + unsigned int i; > > while (s != end) { > - wait_for_lsr(up, UART_LSR_THRE); > + /* Allow timeout for each byte of a possibly full FIFO. */ > + for (i = 0; i < fifosize; i++) { > + if (wait_for_lsr(up, UART_LSR_THRE)) > + break; > + } THRE only signals there is a space for one character. Multiplying it with fifosize does not make much sense to me. You perhaps want only to increase the timeout. Or somehow incorporate port->frame_time into the accounting (I am not sure it is available at this point already). > for (i = 0; i < fifosize && s != end; ++i) { > if (*s == '\n' && !cr_sent) { > @@ -3323,6 +3332,13 @@ static void serial8250_console_fifo_write(struct uart_8250_port *up, > cr_sent = false; > } > } > + tx_count = i; > + } > + > + /* Allow timeout for each byte written. */ > + for (i = 0; i < tx_count; i++) { > + if (wait_for_lsr(up, UART_LSR_THRE)) This ensures you sent one character from the FIFO. The FIFO still can contain plenty of them. Did you want UART_LSR_TEMT? But what's the purpose of spinning _here_? The kernel can run and FIFO too. Without the kernel waiting for the FIFO. thanks, -- js suse labs