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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id z12sm20524905wrg.9.2020.06.22.09.36.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jun 2020 09:36:23 -0700 (PDT) Date: Mon, 22 Jun 2020 17:36:21 +0100 From: Daniel Thompson To: Sumit Garg Cc: kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org, gregkh@linuxfoundation.org, jason.wessel@windriver.com, dianders@chromium.org, jslaby@suse.com, linux@armlinux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/7] serial: kgdb_nmi: Add support for interrupt based fallback Message-ID: <20200622163621.s2322lmlv674bsds@holly.lan> References: <1592835984-28613-1-git-send-email-sumit.garg@linaro.org> <1592835984-28613-5-git-send-email-sumit.garg@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1592835984-28613-5-git-send-email-sumit.garg@linaro.org> Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org On Mon, Jun 22, 2020 at 07:56:21PM +0530, Sumit Garg wrote: > From: Daniel Thompson > > Add a generic NMI fallback to support kgdb NMI console feature which can > be overridden by arch specific implementation. arch_kgdb_ops.enable_nmi should probably be killed off. Given we now have request_nmi() I'm dubious there are any good reasons to use this API. Daniel. > This common fallback mechanism utilizes kgdb IO based interrupt in order > to support entry into kgdb if a user types in kgdb_nmi_magic sequence. So > during NMI console init, NMI handler is installed corresponding to kgdb > IO based NMI which is invoked when a character is pending and that can be > cleared by calling @read_char until it returns NO_POLL_CHAR. > > Signed-off-by: Daniel Thompson > Co-developed-by: Sumit Garg > Signed-off-by: Sumit Garg > --- > drivers/tty/serial/kgdb_nmi.c | 47 ++++++++++++++++++++++++++++++++++++------- > 1 file changed, 40 insertions(+), 7 deletions(-) > > diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c > index b32c6b1..2580f39 100644 > --- a/drivers/tty/serial/kgdb_nmi.c > +++ b/drivers/tty/serial/kgdb_nmi.c > @@ -42,9 +42,46 @@ MODULE_PARM_DESC(magic, "magic sequence to enter NMI debugger (default $3#33)"); > static atomic_t kgdb_nmi_num_readers = ATOMIC_INIT(0); > static struct console *orig_dbg_cons; > > +static int kgdb_nmi_poll_one_knock(void); > + > +static irqreturn_t kgdb_handle_nmi(int irq, void *dev_id) > +{ > + int ret; > + > + if (kgdb_nmi_knock < 0) { > + kgdb_breakpoint(); > + return IRQ_HANDLED; > + } > + > + ret = kgdb_nmi_poll_one_knock(); > + if (ret == NO_POLL_CHAR) > + return IRQ_NONE; > + > + while (ret != 1) { > + ret = kgdb_nmi_poll_one_knock(); > + if (ret == NO_POLL_CHAR) > + return IRQ_HANDLED; > + } > + > + kgdb_breakpoint(); > + return IRQ_HANDLED; > +} > + > static int kgdb_nmi_console_setup(struct console *co, char *options) > { > - arch_kgdb_ops.enable_nmi(1); > + int res; > + > + if (arch_kgdb_ops.enable_nmi) { > + arch_kgdb_ops.enable_nmi(1); > + } else if (dbg_io_ops->request_nmi) { > + res = dbg_io_ops->request_nmi(kgdb_handle_nmi, co); > + if (res) { > + pr_err("ttyNMI0: Cannot request nmi/irq\n"); > + return res; > + } > + } else { > + return -ENODEV; > + } > > /* The NMI console uses the dbg_io_ops to issue console messages. To > * avoid duplicate messages during kdb sessions we must inform kdb's > @@ -328,9 +365,6 @@ int kgdb_register_nmi_console(void) > { > int ret; > > - if (!arch_kgdb_ops.enable_nmi) > - return 0; > - > kgdb_nmi_tty_driver = alloc_tty_driver(1); > if (!kgdb_nmi_tty_driver) { > pr_err("%s: cannot allocate tty\n", __func__); > @@ -380,9 +414,8 @@ int kgdb_unregister_nmi_console(void) > { > int ret; > > - if (!arch_kgdb_ops.enable_nmi) > - return 0; > - arch_kgdb_ops.enable_nmi(0); > + if (arch_kgdb_ops.enable_nmi) > + arch_kgdb_ops.enable_nmi(0); > > ret = unregister_console(&kgdb_nmi_console); > if (ret) > -- > 2.7.4 >