Date:   Wed, 7 Aug 2019 10:35:45 +0800
From:   Wu Hao <hao.wu@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     mdf@...nel.org, linux-fpga@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        linux-doc@...r.kernel.org, atull@...nel.org,
        Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH v4 07/12] fpga: dfl: afu: add error reporting support.

On Mon, Aug 05, 2019 at 05:54:37PM +0200, Greg KH wrote:
> On Sun, Aug 04, 2019 at 06:20:17PM +0800, Wu Hao wrote:
> > Error reporting is one important private feature, it reports error
> > detected on port and accelerated function unit (AFU). It introduces
> > several sysfs interfaces to allow userspace to check and clear
> > errors detected by hardware.
> > 
> > Signed-off-by: Xu Yilun <yilun.xu@...el.com>
> > Signed-off-by: Wu Hao <hao.wu@...el.com>
> > Acked-by: Alan Tull <atull@...nel.org>
> > Signed-off-by: Moritz Fischer <mdf@...nel.org>
> > ---
> > v2: switch to device_add/remove_group for sysfs.
> > v3: update kernel version and date in sysfs doc
> > v4: remove dev_dbg in init/uinit callback function.
> > ---
> >  Documentation/ABI/testing/sysfs-platform-dfl-port |  39 ++++
> >  drivers/fpga/Makefile                             |   1 +
> >  drivers/fpga/dfl-afu-error.c                      | 221 ++++++++++++++++++++++
> >  drivers/fpga/dfl-afu-main.c                       |   4 +
> >  drivers/fpga/dfl-afu.h                            |   4 +
> >  5 files changed, 269 insertions(+)
> >  create mode 100644 drivers/fpga/dfl-afu-error.c
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-platform-dfl-port b/Documentation/ABI/testing/sysfs-platform-dfl-port
> > index 5663441..3b6580b 100644
> > --- a/Documentation/ABI/testing/sysfs-platform-dfl-port
> > +++ b/Documentation/ABI/testing/sysfs-platform-dfl-port
> > @@ -81,3 +81,42 @@ KernelVersion:	5.4
> >  Contact:	Wu Hao <hao.wu@...el.com>
> >  Description:	Read-only. Read this file to get the status of issued command
> >  		to userclck_freqcntrcmd.
> > +
> > +What:		/sys/bus/platform/devices/dfl-port.0/errors/revision
> > +Date:		August 2019
> > +KernelVersion:	5.4
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. Read this file to get the revision of this error
> > +		reporting private feature.
> 
> Same revision question here that I had on an earlier patch.
> 
> 
> > +
> > +What:		/sys/bus/platform/devices/dfl-port.0/errors/errors
> > +Date:		August 2019
> > +KernelVersion:	5.4
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. Read this file to get errors detected on port and
> > +		Accelerated Function Unit (AFU).
> > +
> > +What:		/sys/bus/platform/devices/dfl-port.0/errors/first_error
> > +Date:		August 2019
> > +KernelVersion:	5.4
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. Read this file to get the first error detected by
> > +		hardware.
> > +
> > +What:		/sys/bus/platform/devices/dfl-port.0/errors/first_malformed_req
> > +Date:		August 2019
> > +KernelVersion:	5.4
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Read-only. Read this file to get the first malformed request
> > +		captured by hardware.
> > +
> > +What:		/sys/bus/platform/devices/dfl-port.0/errors/clear
> > +Date:		August 2019
> > +KernelVersion:	5.4
> > +Contact:	Wu Hao <hao.wu@...el.com>
> > +Description:	Write-only. Write error code to this file to clear errors.
> > +		Write fails with -EINVAL if input parsing fails or input error
> > +		code doesn't match.
> > +		Write fails with -EBUSY or -ETIMEDOUT if error can't be cleared
> > +		as hardware is in low power state (-EBUSY) or not responding
> > +		(-ETIMEDOUT).
> > diff --git a/drivers/fpga/Makefile b/drivers/fpga/Makefile
> > index 312b937..7255891 100644
> > --- a/drivers/fpga/Makefile
> > +++ b/drivers/fpga/Makefile
> > @@ -41,6 +41,7 @@ obj-$(CONFIG_FPGA_DFL_AFU)		+= dfl-afu.o
> >  
> >  dfl-fme-objs := dfl-fme-main.o dfl-fme-pr.o
> >  dfl-afu-objs := dfl-afu-main.o dfl-afu-region.o dfl-afu-dma-region.o
> > +dfl-afu-objs += dfl-afu-error.o
> >  
> >  # Drivers for FPGAs which implement DFL
> >  obj-$(CONFIG_FPGA_DFL_PCI)		+= dfl-pci.o
> > diff --git a/drivers/fpga/dfl-afu-error.c b/drivers/fpga/dfl-afu-error.c
> > new file mode 100644
> > index 0000000..c5e0efa
> > --- /dev/null
> > +++ b/drivers/fpga/dfl-afu-error.c
> > @@ -0,0 +1,221 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Driver for FPGA Accelerated Function Unit (AFU) Error Reporting
> > + *
> > + * Copyright 2019 Intel Corporation, Inc.
> > + *
> > + * Authors:
> > + *   Wu Hao <hao.wu@...ux.intel.com>
> > + *   Xiao Guangrong <guangrong.xiao@...ux.intel.com>
> > + *   Joseph Grecco <joe.grecco@...el.com>
> > + *   Enno Luebbers <enno.luebbers@...el.com>
> > + *   Tim Whisonant <tim.whisonant@...el.com>
> > + *   Ananda Ravuri <ananda.ravuri@...el.com>
> > + *   Mitchel Henry <henry.mitchel@...el.com>
> > + */
> > +
> > +#include <linux/uaccess.h>
> > +
> > +#include "dfl-afu.h"
> > +
> > +#define PORT_ERROR_MASK		0x8
> > +#define PORT_ERROR		0x10
> > +#define PORT_FIRST_ERROR	0x18
> > +#define PORT_MALFORMED_REQ0	0x20
> > +#define PORT_MALFORMED_REQ1	0x28
> > +
> > +#define ERROR_MASK		GENMASK_ULL(63, 0)
> > +
> > +/* mask or unmask port errors by the error mask register. */
> > +static void __port_err_mask(struct device *dev, bool mask)
> > +{
> > +	void __iomem *base;
> > +
> > +	base = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_ERROR);
> > +
> > +	writeq(mask ? ERROR_MASK : 0, base + PORT_ERROR_MASK);
> > +}
> > +
> > +/* clear port errors. */
> > +static int __port_err_clear(struct device *dev, u64 err)
> > +{
> > +	struct platform_device *pdev = to_platform_device(dev);
> > +	void __iomem *base_err, *base_hdr;
> > +	int ret;
> > +	u64 v;
> > +
> > +	base_err = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_ERROR);
> > +	base_hdr = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_HEADER);
> > +
> > +	/*
> > +	 * clear Port Errors
> > +	 *
> > +	 * - Check for AP6 State
> > +	 * - Halt Port by keeping Port in reset
> > +	 * - Set PORT Error mask to all 1 to mask errors
> > +	 * - Clear all errors
> > +	 * - Set Port mask to all 0 to enable errors
> > +	 * - All errors start capturing new errors
> > +	 * - Enable Port by pulling the port out of reset
> > +	 */
> > +
> > +	/* if device is still in AP6 power state, can not clear any error. */
> > +	v = readq(base_hdr + PORT_HDR_STS);
> > +	if (FIELD_GET(PORT_STS_PWR_STATE, v) == PORT_STS_PWR_STATE_AP6) {
> > +		dev_err(dev, "Could not clear errors, device in AP6 state.\n");
> > +		return -EBUSY;
> > +	}
> > +
> > +	/* Halt Port by keeping Port in reset */
> > +	ret = __port_disable(pdev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	/* Mask all errors */
> > +	__port_err_mask(dev, true);
> > +
> > +	/* Clear errors if err input matches with current port errors.*/
> > +	v = readq(base_err + PORT_ERROR);
> > +
> > +	if (v == err) {
> > +		writeq(v, base_err + PORT_ERROR);
> > +
> > +		v = readq(base_err + PORT_FIRST_ERROR);
> > +		writeq(v, base_err + PORT_FIRST_ERROR);
> > +	} else {
> > +		ret = -EINVAL;
> > +	}
> > +
> > +	/* Clear mask */
> > +	__port_err_mask(dev, false);
> > +
> > +	/* Enable the Port by clear the reset */
> > +	__port_enable(pdev);
> > +
> > +	return ret;
> > +}
> > +
> > +static ssize_t revision_show(struct device *dev, struct device_attribute *attr,
> > +			     char *buf)
> > +{
> > +	void __iomem *base;
> > +
> > +	base = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_ERROR);
> > +
> > +	return sprintf(buf, "%u\n", dfl_feature_revision(base));
> > +}
> > +static DEVICE_ATTR_RO(revision);
> > +
> > +static ssize_t errors_show(struct device *dev, struct device_attribute *attr,
> > +			   char *buf)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(dev);
> > +	void __iomem *base;
> > +	u64 error;
> > +
> > +	base = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_ERROR);
> > +
> > +	mutex_lock(&pdata->lock);
> > +	error = readq(base + PORT_ERROR);
> > +	mutex_unlock(&pdata->lock);
> > +
> > +	return sprintf(buf, "0x%llx\n", (unsigned long long)error);
> > +}
> > +static DEVICE_ATTR_RO(errors);
> > +
> > +static ssize_t first_error_show(struct device *dev,
> > +				struct device_attribute *attr, char *buf)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(dev);
> > +	void __iomem *base;
> > +	u64 error;
> > +
> > +	base = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_ERROR);
> > +
> > +	mutex_lock(&pdata->lock);
> > +	error = readq(base + PORT_FIRST_ERROR);
> > +	mutex_unlock(&pdata->lock);
> > +
> > +	return sprintf(buf, "0x%llx\n", (unsigned long long)error);
> > +}
> > +static DEVICE_ATTR_RO(first_error);
> > +
> > +static ssize_t first_malformed_req_show(struct device *dev,
> > +					struct device_attribute *attr,
> > +					char *buf)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(dev);
> > +	void __iomem *base;
> > +	u64 req0, req1;
> > +
> > +	base = dfl_get_feature_ioaddr_by_id(dev, PORT_FEATURE_ID_ERROR);
> > +
> > +	mutex_lock(&pdata->lock);
> > +	req0 = readq(base + PORT_MALFORMED_REQ0);
> > +	req1 = readq(base + PORT_MALFORMED_REQ1);
> > +	mutex_unlock(&pdata->lock);
> > +
> > +	return sprintf(buf, "0x%016llx%016llx\n",
> > +		       (unsigned long long)req1, (unsigned long long)req0);
> > +}
> > +static DEVICE_ATTR_RO(first_malformed_req);
> > +
> > +static ssize_t clear_store(struct device *dev, struct device_attribute *attr,
> > +			   const char *buff, size_t count)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(dev);
> > +	u64 value;
> > +	int ret;
> > +
> > +	if (kstrtou64(buff, 0, &value))
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&pdata->lock);
> > +	ret = __port_err_clear(dev, value);
> > +	mutex_unlock(&pdata->lock);
> > +
> > +	return ret ? ret : count;
> > +}
> > +static DEVICE_ATTR_WO(clear);
> > +
> > +static struct attribute *port_err_attrs[] = {
> > +	&dev_attr_revision.attr,
> > +	&dev_attr_errors.attr,
> > +	&dev_attr_first_error.attr,
> > +	&dev_attr_first_malformed_req.attr,
> > +	&dev_attr_clear.attr,
> > +	NULL,
> > +};
> > +
> > +static struct attribute_group port_err_attr_group = {
> > +	.attrs = port_err_attrs,
> > +	.name = "errors",
> > +};
> > +
> > +static int port_err_init(struct platform_device *pdev,
> > +			 struct dfl_feature *feature)
> > +{
> > +	struct dfl_feature_platform_data *pdata = dev_get_platdata(&pdev->dev);
> > +
> > +	mutex_lock(&pdata->lock);
> > +	__port_err_mask(&pdev->dev, false);
> > +	mutex_unlock(&pdata->lock);
> 
> Locking one data structure and then modifying another one is up there
> with "things never to do in the kernel unless you want a huge
> headache!".

Actually we always use the same lock for protection as other places, but
the code may cause some misunderstanding, let me improve this part in
the next version.

> 
> > +
> > +	return device_add_group(&pdev->dev, &port_err_attr_group);
> 
> You raced userspace and lost :(

Do you mind giving some more hints on this one? I guess I didn't fully
understand this. :( Add handling if device_add_group failed here, or
something else I should fix?

Thanks
Hao

> 
> thanks,
> 
> greg k-h

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