From: John Ogness <john.ogness@linutronix.de>
To: Yunhui Cui <cuiyunhui@bytedance.com>,
gregkh@linuxfoundation.org, jirislaby@kernel.org,
pmladek@suse.com, arnd@arndb.de,
andriy.shevchenko@linux.intel.com, namcao@linutronix.de,
benjamin.larsson@genexis.eu, schnelle@linux.ibm.com,
linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
Cc: Yunhui Cui <cuiyunhui@bytedance.com>
Subject: Re: [PATCH] serial: 8250: fix panic due to PSLVERR
Date: Thu, 03 Apr 2025 14:03:58 +0206 [thread overview]
Message-ID: <84iknl5uex.fsf@jogness.linutronix.de> (raw)
In-Reply-To: <20250403090336.16643-1-cuiyunhui@bytedance.com>
On 2025-04-03, Yunhui Cui <cuiyunhui@bytedance.com> wrote:
> When the PSLVERR_RESP_EN parameter is set to 1, the device generates
> an error response if an attempt is made to read an empty RBR (Receive
> Buffer Register) while the FIFO is enabled.
>
> In serial8250_do_startup, calling serial_port_out(port, UART_LCR,
> UART_LCR_WLEN8) triggers dw8250_check_lcr(), which invokes
> dw8250_force_idle() and serial8250_clear_and_reinit_fifos(). The latter
> function enables the FIFO via serial_out(p, UART_FCR, p->fcr).
> Execution proceeds to the dont_test_tx_en label:
> ...
> serial_port_in(port, UART_RX);
> This satisfies the PSLVERR trigger condition.
>
> Because another CPU(e.g., using printk) is accessing the UART (UART
> is busy), the current CPU fails the check (value & ~UART_LCR_SPAR) ==
> (lcr & ~UART_LCR_SPAR), causing it to enter dw8250_force_idle().
Didn't this[0] patch resolve this exact issue?
John Ogness
[0] https://lore.kernel.org/lkml/20220713131722.2316829-1-vamshigajjela@google.com
next prev parent reply other threads:[~2025-04-03 11:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-03 9:03 [PATCH] serial: 8250: fix panic due to PSLVERR Yunhui Cui
2025-04-03 11:36 ` Andy Shevchenko
2025-04-03 11:50 ` Andy Shevchenko
2025-04-04 2:31 ` [External] " yunhui cui
2025-04-04 10:21 ` Andy Shevchenko
2025-04-07 13:00 ` yunhui cui
2025-04-07 14:34 ` Andy Shevchenko
2025-04-04 2:44 ` yunhui cui
2025-04-04 10:58 ` Andy Shevchenko
2025-04-07 13:22 ` yunhui cui
2025-04-07 14:37 ` Andy Shevchenko
2025-04-03 11:57 ` John Ogness [this message]
2025-04-03 12:10 ` Andy Shevchenko
2025-04-03 12:49 ` [External] " yunhui cui
2025-04-03 13:46 ` John Ogness
2025-04-03 14:14 ` yunhui cui
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