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Subject[PATCH 4.20 17/65] media: cx23885: only reset DMA on problematic CPUs
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Brad Love <brad@nextdimension.cc>

commit 4bd46aa0353e022c2401a258e93b107880a66533 upstream.

It is reported that commit 95f408bbc4e4 ("media: cx23885: Ryzen DMA
related RiSC engine stall fixes") caused regresssions with other CPUs.

Ensure that the quirk will be applied only for the CPUs that
are known to cause problems.

A module option is added for explicit control of the behaviour.

Fixes: 95f408bbc4e4 ("media: cx23885: Ryzen DMA related RiSC engine stall fixes")

Signed-off-by: Brad Love <brad@nextdimension.cc>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/media/pci/cx23885/cx23885-core.c | 55 +++++++++++++++++++++++++++++--
drivers/media/pci/cx23885/cx23885.h | 2 +
2 files changed, 55 insertions(+), 2 deletions(-)

--- a/drivers/media/pci/cx23885/cx23885-core.c
+++ b/drivers/media/pci/cx23885/cx23885-core.c
@@ -23,6 +23,7 @@
#include <linux/moduleparam.h>
#include <linux/kmod.h>
#include <linux/kernel.h>
+#include <linux/pci.h>
#include <linux/slab.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
@@ -41,6 +42,18 @@ MODULE_AUTHOR("Steven Toth <stoth@linuxt
MODULE_LICENSE("GPL");
MODULE_VERSION(CX23885_VERSION);

+/*
+ * Some platforms have been found to require periodic resetting of the DMA
+ * engine. Ryzen and XEON platforms are known to be affected. The symptom
+ * encountered is "mpeg risc op code error". Only Ryzen platforms employ
+ * this workaround if the option equals 1. The workaround can be explicitly
+ * disabled for all platforms by setting to 0, the workaround can be forced
+ * on for any platform by setting to 2.
+ */
+static unsigned int dma_reset_workaround = 1;
+module_param(dma_reset_workaround, int, 0644);
+MODULE_PARM_DESC(dma_reset_workaround, "periodic RiSC dma engine reset; 0-force disable, 1-driver detect (default), 2-force enable");
+
static unsigned int debug;
module_param(debug, int, 0644);
MODULE_PARM_DESC(debug, "enable debug messages");
@@ -603,8 +616,13 @@ static void cx23885_risc_disasm(struct c

static void cx23885_clear_bridge_error(struct cx23885_dev *dev)
{
- uint32_t reg1_val = cx_read(TC_REQ); /* read-only */
- uint32_t reg2_val = cx_read(TC_REQ_SET);
+ uint32_t reg1_val, reg2_val;
+
+ if (!dev->need_dma_reset)
+ return;
+
+ reg1_val = cx_read(TC_REQ); /* read-only */
+ reg2_val = cx_read(TC_REQ_SET);

if (reg1_val && reg2_val) {
cx_write(TC_REQ, reg1_val);
@@ -2058,6 +2076,37 @@ void cx23885_gpio_enable(struct cx23885_
/* TODO: 23-19 */
}

+static struct {
+ int vendor, dev;
+} const broken_dev_id[] = {
+ /* According with
+ * https://openbenchmarking.org/system/1703021-RI-AMDZEN08075/Ryzen%207%201800X/lspci,
+ * 0x1451 is PCI ID for the IOMMU found on Ryzen
+ */
+ { PCI_VENDOR_ID_AMD, 0x1451 },
+};
+
+static bool cx23885_does_need_dma_reset(void)
+{
+ int i;
+ struct pci_dev *pdev = NULL;
+
+ if (dma_reset_workaround == 0)
+ return false;
+ else if (dma_reset_workaround == 2)
+ return true;
+
+ for (i = 0; i < ARRAY_SIZE(broken_dev_id); i++) {
+ pdev = pci_get_device(broken_dev_id[i].vendor,
+ broken_dev_id[i].dev, NULL);
+ if (pdev) {
+ pci_dev_put(pdev);
+ return true;
+ }
+ }
+ return false;
+}
+
static int cx23885_initdev(struct pci_dev *pci_dev,
const struct pci_device_id *pci_id)
{
@@ -2069,6 +2118,8 @@ static int cx23885_initdev(struct pci_de
if (NULL == dev)
return -ENOMEM;

+ dev->need_dma_reset = cx23885_does_need_dma_reset();
+
err = v4l2_device_register(&pci_dev->dev, &dev->v4l2_dev);
if (err < 0)
goto fail_free;
--- a/drivers/media/pci/cx23885/cx23885.h
+++ b/drivers/media/pci/cx23885/cx23885.h
@@ -451,6 +451,8 @@ struct cx23885_dev {
/* Analog raw audio */
struct cx23885_audio_dev *audio_dev;

+ /* Does the system require periodic DMA resets? */
+ unsigned int need_dma_reset:1;
};

static inline struct cx23885_dev *to_cx23885(struct v4l2_device *v4l2_dev)

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