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openwrt/target/linux/bcm27xx/patches-6.6/950-1100-drivers-pcie-brcmstb-add-best-effort-workaround-for-.patch
Álvaro Fernández Rojas 8c405cdccc bcm27xx: add 6.6 kernel patches
The patches were generated from the RPi repo with the following command:
git format-patch v6.6.34..rpi-6.1.y

Some patches needed rebasing and, as usual, the applied and reverted, wireless
drivers, Github workflows, READMEs and defconfigs patches were removed.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
2024-06-18 18:52:49 +02:00

43 lines
1.7 KiB
Diff

From 0a19b5256303d2f35be9272832b01a170c9a039b Mon Sep 17 00:00:00 2001
From: Jonathan Bell <jonathan@raspberrypi.com>
Date: Wed, 22 May 2024 09:46:54 +0100
Subject: [PATCH 1100/1135] drivers: pcie-brcmstb: add best-effort workaround
for QoS bug on bcm2712
If a set of read requests are issued by an endpoint, they are streamed
into a resynchronisation FIFO prior to exiting the RC. This FIFO has an
edge case where it can drop QoS for a request to 0 if there's a single
outstanding read request in the FIFO, and another is pushed when the
FIFO is popped. Requests with a QoS of 0 can take hundreds of
microseconds to complete.
By adding an experimentally-determined amount of backpressure on the pop
side, the critical level transition can largely be avoided.
Signed-off-by: Jonathan Bell <jonathan@raspberrypi.com>
---
drivers/pci/controller/pcie-brcmstb.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
--- a/drivers/pci/controller/pcie-brcmstb.c
+++ b/drivers/pci/controller/pcie-brcmstb.c
@@ -568,6 +568,18 @@ static void brcm_pcie_set_tc_qos(struct
AXI_DIS_QOS_GATING_IN_MASTER;
writel(reg, pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+ /*
+ * If the QOS_UPDATE_TIMING_FIX bit is Reserved-0, then this is a
+ * 2712C1 chip, or a single-lane RC. Use the best-effort alternative
+ * which is to partially throttle AXI requests in-flight to the SDC.
+ */
+ reg = readl(pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+ if (!(reg & AXI_EN_QOS_UPDATE_TIMING_FIX)) {
+ reg &= ~AXI_MASTER_MAX_OUTSTANDING_REQUESTS_MASK;
+ reg |= 15;
+ writel(reg, pcie->base + PCIE_MISC_AXI_INTF_CTRL);
+ }
+
/* Disable VDM reception by default - QoS map defaults to 0 */
reg = readl(pcie->base + PCIE_MISC_CTRL_1);
reg &= ~PCIE_MISC_CTRL_1_EN_VDM_QOS_CONTROL_MASK;