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15b9c02d6c
Removed upstreamed:
generic/101-Use-stddefs.h-instead-of-compiler.h.patch[1]
bcm27xx/patches-5.10/950-0194-drm-fourcc-Add-packed-10bit-YUV-4-2-0-format.patch
All patches automatically rebased.
1. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.10.163&id=ddd2bb08bd99b7ee4442fbbe0f9b80236fdd71d2
Build system: x86_64
Build-tested: ramips/tplink_archer-a6-v3
Run-tested: ramips/tplink_archer-a6-v3
Signed-off-by: John Audia <therealgraysky@proton.me>
(cherry picked from commit 2835df54ab)
43 lines
1.7 KiB
Diff
43 lines
1.7 KiB
Diff
From e9addfee683ceabeae5da9dc5503fef536f7385a Mon Sep 17 00:00:00 2001
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From: Phil Elwell <phil@raspberrypi.org>
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Date: Wed, 29 Jan 2020 09:35:19 +0000
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Subject: [PATCH] tty: amba-pl011: Avoid rare write-when-full error
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Under some circumstances on BCM283x processors data loss can be
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observed - a single byte missing from the TX output stream. These bytes
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are always the last byte of a batch of 8 written from pl011_tx_chars
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when from_irq is true, meaning that the FIFO full flag is not checked
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before writing.
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The transmit optimisation relies on the FIFO being half-empty when the
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TX interrupt is raised. Instrumenting the driver further showed that
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the failure case correlated with the TX FIFO full flag being set at the
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point where the last byte was written to the data register, which
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explains the data loss but not how the FIFO appeared to be prematurely
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full. A possible explanation is that a FIFO write was in flight at the
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time the interrupt was raised, but as yet there is no hypothesis as to
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how this might occur.
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In the absence of a clear understanding of the failure mechanism, avoid
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the problem by checking the FIFO levels before writing the last byte of
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the group, which will have minimal performance impact.
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Signed-off-by: Phil Elwell <phil@raspberrypi.org>
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---
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drivers/tty/serial/amba-pl011.c | 4 ++++
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1 file changed, 4 insertions(+)
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--- a/drivers/tty/serial/amba-pl011.c
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+++ b/drivers/tty/serial/amba-pl011.c
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@@ -1424,6 +1424,10 @@ static bool pl011_tx_chars(struct uart_a
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if (likely(from_irq) && count-- == 0)
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break;
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+ if (likely(from_irq) && count == 0 &&
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+ pl011_read(uap, REG_FR) & UART01x_FR_TXFF)
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+ break;
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+
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if (!pl011_tx_char(uap, xmit->buf[xmit->tail], from_irq))
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break;
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