This is a note to let you know that I've just added the patch titled
mmc: cqhci: Avoid false "cqhci: CQE stuck on" by not open-coding timeout loop
to the 5.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mmc-cqhci-avoid-false-cqhci-cqe-stuck-on-by-not-open-coding-timeout-loop.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b1ac62a7ac386d76968af5f374a4a7a82a35fe31 Mon Sep 17 00:00:00 2001
From: Douglas Anderson <dianders@xxxxxxxxxxxx>
Date: Mon, 13 Apr 2020 16:27:27 -0700
Subject: mmc: cqhci: Avoid false "cqhci: CQE stuck on" by not open-coding timeout loop
From: Douglas Anderson <dianders@xxxxxxxxxxxx>
commit b1ac62a7ac386d76968af5f374a4a7a82a35fe31 upstream.
Open-coding a timeout loop invariably leads to errors with handling
the timeout properly in one corner case or another. In the case of
cqhci we might report "CQE stuck on" even if it wasn't stuck on.
You'd just need this sequence of events to happen in cqhci_off():
1. Call ktime_get().
2. Something happens to interrupt the CPU for > 100 us (context switch
or interrupt).
3. Check time and; set "timed_out" to true since > 100 us.
4. Read CQHCI_CTL.
5. Both "reg & CQHCI_HALT" and "timed_out" are true, so break.
6. Since "timed_out" is true, falsely print the error message.
Rather than fixing the polling loop, use readx_poll_timeout() like
many people do. This has been time tested to handle the corner cases.
Fixes: a4080225f51d ("mmc: cqhci: support for command queue enabled host")
Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20200413162717.1.Idece266f5c8793193b57a1ddb1066d030c6af8e0@changeid
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/mmc/host/cqhci.c | 21 ++++++++++-----------
1 file changed, 10 insertions(+), 11 deletions(-)
--- a/drivers/mmc/host/cqhci.c
+++ b/drivers/mmc/host/cqhci.c
@@ -5,6 +5,7 @@
#include <linux/delay.h>
#include <linux/highmem.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/dma-mapping.h>
#include <linux/slab.h>
@@ -343,12 +344,16 @@ static int cqhci_enable(struct mmc_host
/* CQHCI is idle and should halt immediately, so set a small timeout */
#define CQHCI_OFF_TIMEOUT 100
+static u32 cqhci_read_ctl(struct cqhci_host *cq_host)
+{
+ return cqhci_readl(cq_host, CQHCI_CTL);
+}
+
static void cqhci_off(struct mmc_host *mmc)
{
struct cqhci_host *cq_host = mmc->cqe_private;
- ktime_t timeout;
- bool timed_out;
u32 reg;
+ int err;
if (!cq_host->enabled || !mmc->cqe_on || cq_host->recovery_halt)
return;
@@ -358,15 +363,9 @@ static void cqhci_off(struct mmc_host *m
cqhci_writel(cq_host, CQHCI_HALT, CQHCI_CTL);
- timeout = ktime_add_us(ktime_get(), CQHCI_OFF_TIMEOUT);
- while (1) {
- timed_out = ktime_compare(ktime_get(), timeout) > 0;
- reg = cqhci_readl(cq_host, CQHCI_CTL);
- if ((reg & CQHCI_HALT) || timed_out)
- break;
- }
-
- if (timed_out)
+ err = readx_poll_timeout(cqhci_read_ctl, cq_host, reg,
+ reg & CQHCI_HALT, 0, CQHCI_OFF_TIMEOUT);
+ if (err < 0)
pr_err("%s: cqhci: CQE stuck on\n", mmc_hostname(mmc));
else
pr_debug("%s: cqhci: CQE off\n", mmc_hostname(mmc));
Patches currently in stable-queue which might be from dianders@xxxxxxxxxxxx are
queue-5.6/mmc-cqhci-avoid-false-cqhci-cqe-stuck-on-by-not-open-coding-timeout-loop.patch
