[BACKPORT 4.14.y v2 0/6] Candidates from Spreadtrum 4.14 product kernel

[BACKPORT 4.14.y v2 0/6] Candidates from Spreadtrum 4.14 product kernel

[Baolin Wang]

With Arnd's script [1] help, I found some bugfixes in Spreadtrum 4.14 product
kernel, but missing in v4.14.141:

25a09ce79639 ppp: mppe: Revert "ppp: mppe: Add softdep to arc4"
47d3d7fdb10a ip6: fix skb leak in ip6frag_expire_frag_queue()
5b9cea15a3de serial: sprd: Modify the baud rate calculation formula
513e1073d52e locking/lockdep: Add debug_locks check in __lock_downgrade()
957063c92473 pinctrl: sprd: Use define directive for sprd_pinconf_params values
87a2b65fc855 power: supply: sysfs: ratelimit property read error message

[1] https://lore.kernel.org/lkml/20190322154425.3852517-19-arnd@arndb.de/T/

Changes from v1:
 - Drop 2 unnecessary patches (patch 1 and patch 4) from v1 patch set.
 - Add upstream commit id in change log for each stable patch.

David Lechner (1):
  power: supply: sysfs: ratelimit property read error message

Eric Biggers (1):
  ppp: mppe: Revert "ppp: mppe: Add softdep to arc4"

Eric Dumazet (1):
  ip6: fix skb leak in ip6frag_expire_frag_queue()

Lanqing Liu (1):
  serial: sprd: Modify the baud rate calculation formula

Nathan Chancellor (1):
  pinctrl: sprd: Use define directive for sprd_pinconf_params values

Waiman Long (1):
  locking/lockdep: Add debug_locks check in __lock_downgrade()

 drivers/net/ppp/ppp_mppe.c                |    1 -
 drivers/pinctrl/sprd/pinctrl-sprd.c       |    6 ++----
 drivers/power/supply/power_supply_sysfs.c |    3 ++-
 drivers/tty/serial/sprd_serial.c          |    2 +-
 include/net/ipv6_frag.h                   |    1 -
 kernel/locking/lockdep.c                  |    3 +++
 6 files changed, 8 insertions(+), 8 deletions(-)

-- 
1.7.9.5

[BACKPORT 4.14.y v2 1/6] ip6: fix skb leak in ip6frag_expire_frag_queue()

[Baolin Wang]

From: Eric Dumazet <edumazet@google.com>

[Upstream commit 47d3d7fdb10a21c223036b58bd70ffdc24a472c4]

Since ip6frag_expire_frag_queue() now pulls the head skb
from frag queue, we should no longer use skb_get(), since
this leads to an skb leak.

Stefan Bader initially reported a problem in 4.4.stable [1] caused
by the skb_get(), so this patch should also fix this issue.

296583.091021] kernel BUG at /build/linux-6VmqmP/linux-4.4.0/net/core/skbuff.c:1207!
[296583.091734] Call Trace:
[296583.091749]  [<ffffffff81740e50>] __pskb_pull_tail+0x50/0x350
[296583.091764]  [<ffffffff8183939a>] _decode_session6+0x26a/0x400
[296583.091779]  [<ffffffff817ec719>] __xfrm_decode_session+0x39/0x50
[296583.091795]  [<ffffffff818239d0>] icmpv6_route_lookup+0xf0/0x1c0
[296583.091809]  [<ffffffff81824421>] icmp6_send+0x5e1/0x940
[296583.091823]  [<ffffffff81753238>] ? __netif_receive_skb+0x18/0x60
[296583.091838]  [<ffffffff817532b2>] ? netif_receive_skb_internal+0x32/0xa0
[296583.091858]  [<ffffffffc0199f74>] ? ixgbe_clean_rx_irq+0x594/0xac0 [ixgbe]
[296583.091876]  [<ffffffffc04eb260>] ? nf_ct_net_exit+0x50/0x50 [nf_defrag_ipv6]
[296583.091893]  [<ffffffff8183d431>] icmpv6_send+0x21/0x30
[296583.091906]  [<ffffffff8182b500>] ip6_expire_frag_queue+0xe0/0x120
[296583.091921]  [<ffffffffc04eb27f>] nf_ct_frag6_expire+0x1f/0x30 [nf_defrag_ipv6]
[296583.091938]  [<ffffffff810f3b57>] call_timer_fn+0x37/0x140
[296583.091951]  [<ffffffffc04eb260>] ? nf_ct_net_exit+0x50/0x50 [nf_defrag_ipv6]
[296583.091968]  [<ffffffff810f5464>] run_timer_softirq+0x234/0x330
[296583.091982]  [<ffffffff8108a339>] __do_softirq+0x109/0x2b0

Fixes: d4289fcc9b16 ("net: IP6 defrag: use rbtrees for IPv6 defrag")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Stefan Bader <stefan.bader@canonical.com>
Cc: Peter Oskolkov <posk@google.com>
Cc: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 include/net/ipv6_frag.h |    1 -
 1 file changed, 1 deletion(-)

diff --git a/include/net/ipv6_frag.h b/include/net/ipv6_frag.h
index 28aa9b3..1f77fb4 100644
--- a/include/net/ipv6_frag.h
+++ b/include/net/ipv6_frag.h
@@ -94,7 +94,6 @@ static inline u32 ip6frag_obj_hashfn(const void *data, u32 len, u32 seed)
 		goto out;
 
 	head->dev = dev;
-	skb_get(head);
 	spin_unlock(&fq->q.lock);
 
 	icmpv6_send(head, ICMPV6_TIME_EXCEED, ICMPV6_EXC_FRAGTIME, 0);
-- 
1.7.9.5

[BACKPORT 4.14.y v2 2/6] locking/lockdep: Add debug_locks check in __lock_downgrade()

[Baolin Wang]

From: Waiman Long <longman@redhat.com>

[Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf]

Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
warning right after a previous lockdep warning. It is likely that the
previous warning turned off lock debugging causing the lockdep to have
inconsistency states leading to the lock downgrade warning.

Fix that by add a check for debug_locks at the beginning of
__lock_downgrade().

Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 kernel/locking/lockdep.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 565005a..5c370c6 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3650,6 +3650,9 @@ static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
 	unsigned int depth;
 	int i;
 
+	if (unlikely(!debug_locks))
+		return 0;
+
 	depth = curr->lockdep_depth;
 	/*
 	 * This function is about (re)setting the class of a held lock,
-- 
1.7.9.5

Re: [BACKPORT 4.14.y v2 2/6] locking/lockdep: Add debug_locks check in __lock_downgrade()

[Greg KH]

On Thu, Sep 05, 2019 at 11:07:14AM +0800, Baolin Wang wrote:
> From: Waiman Long <longman@redhat.com>
> 
> [Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf]
> 
> Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
> warning right after a previous lockdep warning. It is likely that the
> previous warning turned off lock debugging causing the lockdep to have
> inconsistency states leading to the lock downgrade warning.
> 
> Fix that by add a check for debug_locks at the beginning of
> __lock_downgrade().
> 
> Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com
> Signed-off-by: Waiman Long <longman@redhat.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Will Deacon <will.deacon@arm.com>
> Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
>  kernel/locking/lockdep.c |    3 +++
>  1 file changed, 3 insertions(+)

Why isn't this relevant for 4.19.y?  I can't add a patch to 4.14.y and
then have someone upgrade to 4.19.y and not have the same fix in there,
that would be a regression.

So can you redo this series also with a 4.19.y set at the same so we
don't get out of sync?  I've queued up your first patch already as that
was in 4.19.y (and also needed in 4.9.y).

thanks,

greg k-h

Re: [BACKPORT 4.14.y v2 2/6] locking/lockdep: Add debug_locks check in __lock_downgrade()

[Baolin Wang]

On Tue, 10 Sep 2019 at 22:32, Greg KH <greg@kroah.com> wrote:
>
> On Thu, Sep 05, 2019 at 11:07:14AM +0800, Baolin Wang wrote:
> > From: Waiman Long <longman@redhat.com>
> >
> > [Upstream commit 513e1073d52e55b8024b4f238a48de7587c64ccf]
> >
> > Tetsuo Handa had reported he saw an incorrect "downgrading a read lock"
> > warning right after a previous lockdep warning. It is likely that the
> > previous warning turned off lock debugging causing the lockdep to have
> > inconsistency states leading to the lock downgrade warning.
> >
> > Fix that by add a check for debug_locks at the beginning of
> > __lock_downgrade().
> >
> > Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> > Reported-by: syzbot+53383ae265fb161ef488@syzkaller.appspotmail.com
> > Signed-off-by: Waiman Long <longman@redhat.com>
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Linus Torvalds <torvalds@linux-foundation.org>
> > Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Will Deacon <will.deacon@arm.com>
> > Link: https://lkml.kernel.org/r/1547093005-26085-1-git-send-email-longman@redhat.com
> > Signed-off-by: Ingo Molnar <mingo@kernel.org>
> > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > ---
> >  kernel/locking/lockdep.c |    3 +++
> >  1 file changed, 3 insertions(+)
>
> Why isn't this relevant for 4.19.y?  I can't add a patch to 4.14.y and
> then have someone upgrade to 4.19.y and not have the same fix in there,
> that would be a regression.
>
> So can you redo this series also with a 4.19.y set at the same so we
> don't get out of sync?  I've queued up your first patch already as that
> was in 4.19.y (and also needed in 4.9.y).

I understood, will do. Thanks.

-- 
Baolin Wang
Best Regards

[BACKPORT 4.14.y v2 3/6] pinctrl: sprd: Use define directive for sprd_pinconf_params values

[Baolin Wang]

From: Nathan Chancellor <natechancellor@gmail.com>

[Upstream commit 957063c924736d4341e5d588757b9f31e8f6fa24]

Clang warns when one enumerated type is implicitly converted to another:

drivers/pinctrl/sprd/pinctrl-sprd.c:845:19: warning: implicit conversion
from enumeration type 'enum sprd_pinconf_params' to different
enumeration type 'enum pin_config_param' [-Wenum-conversion]
        {"sprd,control", SPRD_PIN_CONFIG_CONTROL, 0},
        ~                ^~~~~~~~~~~~~~~~~~~~~~~
drivers/pinctrl/sprd/pinctrl-sprd.c:846:22: warning: implicit conversion
from enumeration type 'enum sprd_pinconf_params' to different
enumeration type 'enum pin_config_param' [-Wenum-conversion]
        {"sprd,sleep-mode", SPRD_PIN_CONFIG_SLEEP_MODE, 0},
        ~                   ^~~~~~~~~~~~~~~~~~~~~~~~~~

It is expected that pinctrl drivers can extend pin_config_param because
of the gap between PIN_CONFIG_END and PIN_CONFIG_MAX so this conversion
isn't an issue. Most drivers that take advantage of this define the
PIN_CONFIG variables as constants, rather than enumerated values. Do the
same thing here so that Clang no longer warns.

Link: https://github.com/ClangBuiltLinux/linux/issues/138
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 drivers/pinctrl/sprd/pinctrl-sprd.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/pinctrl/sprd/pinctrl-sprd.c b/drivers/pinctrl/sprd/pinctrl-sprd.c
index 6352991..83958bd 100644
--- a/drivers/pinctrl/sprd/pinctrl-sprd.c
+++ b/drivers/pinctrl/sprd/pinctrl-sprd.c
@@ -159,10 +159,8 @@ struct sprd_pinctrl {
 	struct sprd_pinctrl_soc_info *info;
 };
 
-enum sprd_pinconf_params {
-	SPRD_PIN_CONFIG_CONTROL = PIN_CONFIG_END + 1,
-	SPRD_PIN_CONFIG_SLEEP_MODE = PIN_CONFIG_END + 2,
-};
+#define SPRD_PIN_CONFIG_CONTROL		(PIN_CONFIG_END + 1)
+#define SPRD_PIN_CONFIG_SLEEP_MODE	(PIN_CONFIG_END + 2)
 
 static int sprd_pinctrl_get_id_by_name(struct sprd_pinctrl *sprd_pctl,
 				       const char *name)
-- 
1.7.9.5

[BACKPORT 4.14.y v2 4/6] power: supply: sysfs: ratelimit property read error message

[Baolin Wang]

From: David Lechner <david@lechnology.com>

[Upstream commit 87a2b65fc855e6be50f791c2ebbb492541896827]

This adds rate limiting to the message that is printed when reading a
power supply property via sysfs returns an error. This will prevent
userspace applications from unintentionally dDOSing the system by
continuously reading a property that returns an error.

Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 drivers/power/supply/power_supply_sysfs.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
index eb5dc74..2ccaf4f 100644
--- a/drivers/power/supply/power_supply_sysfs.c
+++ b/drivers/power/supply/power_supply_sysfs.c
@@ -91,7 +91,8 @@ static ssize_t power_supply_show_property(struct device *dev,
 				dev_dbg(dev, "driver has no data for `%s' property\n",
 					attr->attr.name);
 			else if (ret != -ENODEV && ret != -EAGAIN)
-				dev_err(dev, "driver failed to report `%s' property: %zd\n",
+				dev_err_ratelimited(dev,
+					"driver failed to report `%s' property: %zd\n",
 					attr->attr.name, ret);
 			return ret;
 		}
-- 
1.7.9.5

[BACKPORT 4.14.y v2 5/6] ppp: mppe: Revert "ppp: mppe: Add softdep to arc4"

[Baolin Wang]

From: Eric Biggers <ebiggers@google.com>

[Upstream commit 25a09ce79639a8775244808c17282c491cff89cf]

Commit 0e5a610b5ca5 ("ppp: mppe: switch to RC4 library interface"),
which was merged through the crypto tree for v5.3, changed ppp_mppe.c to
use the new arc4_crypt() library function rather than access RC4 through
the dynamic crypto_skcipher API.

Meanwhile commit aad1dcc4f011 ("ppp: mppe: Add softdep to arc4") was
merged through the net tree and added a module soft-dependency on "arc4".

The latter commit no longer makes sense because the code now uses the
"libarc4" module rather than "arc4", and also due to the direct use of
arc4_crypt(), no module soft-dependency is required.

So revert the latter commit.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 drivers/net/ppp/ppp_mppe.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c
index d9eda7c..6c7fd98 100644
--- a/drivers/net/ppp/ppp_mppe.c
+++ b/drivers/net/ppp/ppp_mppe.c
@@ -63,7 +63,6 @@
 MODULE_DESCRIPTION("Point-to-Point Protocol Microsoft Point-to-Point Encryption support");
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
-MODULE_SOFTDEP("pre: arc4");
 MODULE_VERSION("1.0.2");
 
 static unsigned int
-- 
1.7.9.5

Re: [BACKPORT 4.14.y v2 5/6] ppp: mppe: Revert "ppp: mppe: Add softdep to arc4"

[Eric Biggers]

On Thu, Sep 05, 2019 at 11:10:45AM +0800, Baolin Wang wrote:
> From: Eric Biggers <ebiggers@google.com>
> 
> [Upstream commit 25a09ce79639a8775244808c17282c491cff89cf]
> 
> Commit 0e5a610b5ca5 ("ppp: mppe: switch to RC4 library interface"),
> which was merged through the crypto tree for v5.3, changed ppp_mppe.c to
> use the new arc4_crypt() library function rather than access RC4 through
> the dynamic crypto_skcipher API.
> 
> Meanwhile commit aad1dcc4f011 ("ppp: mppe: Add softdep to arc4") was
> merged through the net tree and added a module soft-dependency on "arc4".
> 
> The latter commit no longer makes sense because the code now uses the
> "libarc4" module rather than "arc4", and also due to the direct use of
> arc4_crypt(), no module soft-dependency is required.
> 
> So revert the latter commit.
> 
> Cc: Takashi Iwai <tiwai@suse.de>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
>  drivers/net/ppp/ppp_mppe.c |    1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c
> index d9eda7c..6c7fd98 100644
> --- a/drivers/net/ppp/ppp_mppe.c
> +++ b/drivers/net/ppp/ppp_mppe.c
> @@ -63,7 +63,6 @@
>  MODULE_DESCRIPTION("Point-to-Point Protocol Microsoft Point-to-Point Encryption support");
>  MODULE_LICENSE("Dual BSD/GPL");
>  MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
> -MODULE_SOFTDEP("pre: arc4");

Why is this being backported?  This revert was only needed because of a
different patch that was merged in v5.3, as I explained in the commit message.

- Eric

Re: [BACKPORT 4.14.y v2 5/6] ppp: mppe: Revert "ppp: mppe: Add softdep to arc4"

[Baolin Wang]

On Fri, 6 Sep 2019 at 00:16, Eric Biggers <ebiggers@google.com> wrote:
>
> On Thu, Sep 05, 2019 at 11:10:45AM +0800, Baolin Wang wrote:
> > From: Eric Biggers <ebiggers@google.com>
> >
> > [Upstream commit 25a09ce79639a8775244808c17282c491cff89cf]
> >
> > Commit 0e5a610b5ca5 ("ppp: mppe: switch to RC4 library interface"),
> > which was merged through the crypto tree for v5.3, changed ppp_mppe.c to
> > use the new arc4_crypt() library function rather than access RC4 through
> > the dynamic crypto_skcipher API.
> >
> > Meanwhile commit aad1dcc4f011 ("ppp: mppe: Add softdep to arc4") was
> > merged through the net tree and added a module soft-dependency on "arc4".
> >
> > The latter commit no longer makes sense because the code now uses the
> > "libarc4" module rather than "arc4", and also due to the direct use of
> > arc4_crypt(), no module soft-dependency is required.
> >
> > So revert the latter commit.
> >
> > Cc: Takashi Iwai <tiwai@suse.de>
> > Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> > Signed-off-by: Eric Biggers <ebiggers@google.com>
> > Signed-off-by: David S. Miller <davem@davemloft.net>
> > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > ---
> >  drivers/net/ppp/ppp_mppe.c |    1 -
> >  1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/net/ppp/ppp_mppe.c b/drivers/net/ppp/ppp_mppe.c
> > index d9eda7c..6c7fd98 100644
> > --- a/drivers/net/ppp/ppp_mppe.c
> > +++ b/drivers/net/ppp/ppp_mppe.c
> > @@ -63,7 +63,6 @@
> >  MODULE_DESCRIPTION("Point-to-Point Protocol Microsoft Point-to-Point Encryption support");
> >  MODULE_LICENSE("Dual BSD/GPL");
> >  MODULE_ALIAS("ppp-compress-" __stringify(CI_MPPE));
> > -MODULE_SOFTDEP("pre: arc4");
>
> Why is this being backported?  This revert was only needed because of a
> different patch that was merged in v5.3, as I explained in the commit message.

Sorry I missed this. I should remove this patch from our product kernel too.

-- 
Baolin Wang
Best Regards

[BACKPORT 4.14.y v2 6/6] serial: sprd: Modify the baud rate calculation formula

[Baolin Wang]

From: Lanqing Liu <lanqing.liu@unisoc.com>

[Upstream commit 5b9cea15a3de5d65000d49f626b71b00d42a0577]

When the source clock is not divisible by the expected baud rate and
the remainder is not less than half of the expected baud rate, the old
formular will round up the frequency division coefficient. This will
make the actual baud rate less than the expected value and can not meet
the external transmission requirements.

Thus this patch modifies the baud rate calculation formula to support
the serial controller output the maximum baud rate.

Signed-off-by: Lanqing Liu <lanqing.liu@unisoc.com>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
 drivers/tty/serial/sprd_serial.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
index e902494..72e96ab8 100644
--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -380,7 +380,7 @@ static void sprd_set_termios(struct uart_port *port,
 	/* ask the core to calculate the divisor for us */
 	baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
 
-	quot = (unsigned int)((port->uartclk + baud / 2) / baud);
+	quot = port->uartclk / baud;
 
 	/* set data length */
 	switch (termios->c_cflag & CSIZE) {
-- 
1.7.9.5

Re: [BACKPORT 4.14.y v2 6/6] serial: sprd: Modify the baud rate calculation formula

[Johan Hovold]

On Thu, Sep 05, 2019 at 11:11:26AM +0800, Baolin Wang wrote:
> From: Lanqing Liu <lanqing.liu@unisoc.com>
> 
> [Upstream commit 5b9cea15a3de5d65000d49f626b71b00d42a0577]
> 
> When the source clock is not divisible by the expected baud rate and
> the remainder is not less than half of the expected baud rate, the old
> formular will round up the frequency division coefficient. This will
> make the actual baud rate less than the expected value and can not meet
> the external transmission requirements.
> 
> Thus this patch modifies the baud rate calculation formula to support
> the serial controller output the maximum baud rate.
> 
> Signed-off-by: Lanqing Liu <lanqing.liu@unisoc.com>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
>  drivers/tty/serial/sprd_serial.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> index e902494..72e96ab8 100644
> --- a/drivers/tty/serial/sprd_serial.c
> +++ b/drivers/tty/serial/sprd_serial.c
> @@ -380,7 +380,7 @@ static void sprd_set_termios(struct uart_port *port,
>  	/* ask the core to calculate the divisor for us */
>  	baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
>  
> -	quot = (unsigned int)((port->uartclk + baud / 2) / baud);
> +	quot = port->uartclk / baud;

Are you sure the original patch is even correct?

By replacing the divisor rounding with truncation you are introducing
larger errors for some baud rates, something which could possibly even
break working systems.

Perhaps the original patch should even be reverted, but in any case
backporting this to stable looks questionable.

>  
>  	/* set data length */
>  	switch (termios->c_cflag & CSIZE) {

Johan

Re: [BACKPORT 4.14.y v2 6/6] serial: sprd: Modify the baud rate calculation formula

[Baolin Wang]

Hi Johan,

On Thu, 5 Sep 2019 at 17:01, Johan Hovold <johan@kernel.org> wrote:
>
> On Thu, Sep 05, 2019 at 11:11:26AM +0800, Baolin Wang wrote:
> > From: Lanqing Liu <lanqing.liu@unisoc.com>
> >
> > [Upstream commit 5b9cea15a3de5d65000d49f626b71b00d42a0577]
> >
> > When the source clock is not divisible by the expected baud rate and
> > the remainder is not less than half of the expected baud rate, the old
> > formular will round up the frequency division coefficient. This will
> > make the actual baud rate less than the expected value and can not meet
> > the external transmission requirements.
> >
> > Thus this patch modifies the baud rate calculation formula to support
> > the serial controller output the maximum baud rate.
> >
> > Signed-off-by: Lanqing Liu <lanqing.liu@unisoc.com>
> > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > ---
> >  drivers/tty/serial/sprd_serial.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> > index e902494..72e96ab8 100644
> > --- a/drivers/tty/serial/sprd_serial.c
> > +++ b/drivers/tty/serial/sprd_serial.c
> > @@ -380,7 +380,7 @@ static void sprd_set_termios(struct uart_port *port,
> >       /* ask the core to calculate the divisor for us */
> >       baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
> >
> > -     quot = (unsigned int)((port->uartclk + baud / 2) / baud);
> > +     quot = port->uartclk / baud;
>
> Are you sure the original patch is even correct?
>
> By replacing the divisor rounding with truncation you are introducing
> larger errors for some baud rates, something which could possibly even
> break working systems.

Our UART clock source is 26M, and there is no difference for lower
than 3M baud rate between dividing closest or dividing down. But we
have one special use case is our BT/GPS want to set 3.25M baud rate,
but we have to select 3M baud rate in baud_table since no 3.25M
setting. So in this case if we use the old formula, we will only get
about 2.8M baud rate, which can not meet our requirement. If we change
the dividing down method, we can get 3.25M baud rate.

I have to say this is a workaroud for our special case, and can solve
our problem. If you have any good suggestion, we can change to a
better solution. Thanks.

>
> Perhaps the original patch should even be reverted, but in any case
> backporting this to stable looks questionable.
>
> >
> >       /* set data length */
> >       switch (termios->c_cflag & CSIZE) {
>
> Johan



-- 
Baolin Wang
Best Regards

Re: [BACKPORT 4.14.y v2 6/6] serial: sprd: Modify the baud rate calculation formula

[Johan Hovold]

On Thu, Sep 05, 2019 at 05:58:05PM +0800, Baolin Wang wrote:
> Hi Johan,
> 
> On Thu, 5 Sep 2019 at 17:01, Johan Hovold <johan@kernel.org> wrote:
> >
> > On Thu, Sep 05, 2019 at 11:11:26AM +0800, Baolin Wang wrote:
> > > From: Lanqing Liu <lanqing.liu@unisoc.com>
> > >
> > > [Upstream commit 5b9cea15a3de5d65000d49f626b71b00d42a0577]
> > >
> > > When the source clock is not divisible by the expected baud rate and
> > > the remainder is not less than half of the expected baud rate, the old
> > > formular will round up the frequency division coefficient. This will
> > > make the actual baud rate less than the expected value and can not meet
> > > the external transmission requirements.
> > >
> > > Thus this patch modifies the baud rate calculation formula to support
> > > the serial controller output the maximum baud rate.
> > >
> > > Signed-off-by: Lanqing Liu <lanqing.liu@unisoc.com>
> > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> > > ---
> > >  drivers/tty/serial/sprd_serial.c |    2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> > > index e902494..72e96ab8 100644
> > > --- a/drivers/tty/serial/sprd_serial.c
> > > +++ b/drivers/tty/serial/sprd_serial.c
> > > @@ -380,7 +380,7 @@ static void sprd_set_termios(struct uart_port *port,
> > >       /* ask the core to calculate the divisor for us */
> > >       baud = uart_get_baud_rate(port, termios, old, 0, SPRD_BAUD_IO_LIMIT);
> > >
> > > -     quot = (unsigned int)((port->uartclk + baud / 2) / baud);
> > > +     quot = port->uartclk / baud;
> >
> > Are you sure the original patch is even correct?
> >
> > By replacing the divisor rounding with truncation you are introducing
> > larger errors for some baud rates, something which could possibly even
> > break working systems.
> 
> Our UART clock source is 26M, and there is no difference for lower
> than 3M baud rate between dividing closest or dividing down.

But there is; you have introduced larger errors for at least a few
standard rates by changing to truncation.

> But we have one special use case is our BT/GPS want to set 3.25M baud
> rate, but we have to select 3M baud rate in baud_table since no 3.25M
> setting. So in this case if we use the old formula, we will only get
> about 2.8M baud rate, which can not meet our requirement. If we change
> the dividing down method, we can get 3.25M baud rate.
> 
> I have to say this is a workaroud for our special case, and can solve
> our problem. If you have any good suggestion, we can change to a
> better solution. Thanks.

Yeah, I don't think purposefully introducing larger errors, and risk
breaking other people's setups, to work around that use case is
warranted.

We have an interface for setting arbitrary baudrates (TCSETS2) which you
can you use (even if glibc support is still not in place). You'd just
need to lift the seemingly arbitrary limitation to 3 Mbaud in the driver
first.

> > Perhaps the original patch should even be reverted, but in any case
> > backporting this to stable looks questionable.

So I think reverting this may be the right thing to do.

Johan