From: Muni Sekhar <munisekharrms@gmail.com>
To: linux-pci@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: pcie: xilinx: kernel hang - ISR readl()
Date: Tue, 7 Jan 2020 21:45:13 +0530 [thread overview]
Message-ID: <CAHhAz+ijBTp55gZYAejWthnvdmR_qyQJpVV4r1gyQ-Kud6t9qg@mail.gmail.com> (raw)
Hi,
I have module with Xilinx FPGA. It implements UART(s), SPI(s),
parallel I/O and interfaces them to the Host CPU via PCI Express bus.
I see that my system freezes without capturing the crash dump for
certain tests. I debugged this issue and it was tracked down to the
below mentioned interrupt handler code.
In ISR, first reads the Interrupt Status register using ‘readl()’ as
given below.
status = readl(ctrl->reg + INT_STATUS);
And then clears the pending interrupts using ‘writel()’ as given blow.
writel(status, ctrl->reg + INT_STATUS);
I've noticed a kernel hang if INT_STATUS register read again after
clearing the pending interrupts.
Can someone clarify me why the kernel hangs without crash dump incase
if I read the INT_STATUS register using readl() after clearing the
pending bits?
Can readl() block?
Snippet of the ISR code is given blow:
https://pastebin.com/WdnZJZF5
static irqreturn_t pcie_isr(int irq, void *dev_id)
{
struct test_device *ctrl = data;
u32 status;
…
status = readl(ctrl->reg + INT_STATUS);
/*
* Check to see if it was our interrupt
*/
if (!(status & 0x000C))
return IRQ_NONE;
/* Clear the interrupt */
writel(status, ctrl->reg + INT_STATUS);
if (status & 0x0004) {
/*
* Tx interrupt pending.
*/
....
}
if (status & 0x0008) {
/* Rx interrupt Pending */
/* The system freezes if I read again the INT_STATUS
register as given below */
status = readl(ctrl->reg + INT_STATUS);
....
}
..
return IRQ_HANDLED;
}
--
Thanks,
Sekhar
next reply other threads:[~2020-01-07 16:15 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-07 16:15 Muni Sekhar [this message]
2020-01-08 14:33 ` pcie: xilinx: kernel hang - ISR readl() Muni Sekhar
2020-01-08 20:15 ` Bjorn Helgaas
2020-01-09 3:17 ` Muni Sekhar
2020-01-09 4:35 ` Bjorn Helgaas
2020-01-09 4:50 ` Muni Sekhar
2020-01-18 1:46 ` Muni Sekhar
2020-01-28 17:40 ` Bjorn Helgaas
2020-01-30 16:07 ` Muni Sekhar
2020-01-30 19:00 ` Bjorn Helgaas
2020-01-31 11:33 ` David Laight
2020-01-31 16:34 ` Muni Sekhar
2020-01-31 20:46 ` Bjorn Helgaas
2020-02-01 3:14 ` Muni Sekhar
2020-02-01 18:29 ` Bjorn Helgaas
2020-02-04 15:33 ` Muni Sekhar
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAHhAz+ijBTp55gZYAejWthnvdmR_qyQJpVV4r1gyQ-Kud6t9qg@mail.gmail.com \
--to=munisekharrms@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).