On Wed, 2015-05-20 at 22:31 +1000, Michael Neuling wrote:

On Wed, 2015-05-20 at 22:12 +1000, Michael Neuling wrote:

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On Wed, 2015-05-20 at 16:26 +0530, Vaibhav Jain wrote:

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Export the "AFU Error Buffer" via sysfs attribute (afu_err_buf). AFU
error buffer is used by the AFU to report application specific
errors. The contents of this buffer are AFU specific and are intended=

 to

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be interpreted by the application interacting with the afu.
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Testing:
	- Build against pseries le/be configs.
	- Run testing with a special version of memcpy afu on a 'be'
	kernel.
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Change-log:
v1 -> v2
	- Simplified cxl_afu_read_err_buffer to handle unaligned reads
	by performing a short read.
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Signed-off-by: Vaibhav Jain <redacted>
---
 Documentation/ABI/testing/sysfs-class-cxl | 11 ++++++
 drivers/misc/cxl/cxl.h                    |  7 ++++
 drivers/misc/cxl/pci.c                    | 60 +++++++++++++++++++++=

++++++++++

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 drivers/misc/cxl/sysfs.c                  | 33 +++++++++++++++++
 4 files changed, 111 insertions(+)
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diff --git a/Documentation/ABI/testing/sysfs-class-cxl b/Documentatio=

n/ABI/testing/sysfs-class-cxl

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index d46bba8..45e9ce3 100644

--- a/Documentation/ABI/testing/sysfs-class-cxl
+++ b/Documentation/ABI/testing/sysfs-class-cxl

@@ -6,6 +6,17 @@ Example: The real path of the attribute /sys/class/c=

xl/afu0.0s/irqs_max is

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 Slave contexts (eg. /sys/class/cxl/afu0.0s):
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+What:           /sys/class/cxl/<afu>/afu_err_buf
+Date:           September 2014
+Contact:        linuxppc-dev@lists.ozlabs.org
+Description:    read only
+                AFU Error Buffer contents. The contents of this file=

 are

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+		application specific and depends on the AFU being used.
+		Applications interacting with the AFU can use this attribute
+		to know about the current error condition and take appropriate
+		action like logging the event etc.
+
+
 What:           /sys/class/cxl/<afu>/irqs_max
 Date:           September 2014
 Contact:        linuxppc-dev@lists.ozlabs.org

diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index a1cee47..789f077 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h

@@ -362,6 +362,10 @@ struct cxl_afu {
 	struct mutex spa_mutex;
 	spinlock_t afu_cntl_lock;

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+	/* AFU error buffer fields and bin attribute for sysfs */
+	u64 eb_len, eb_offset;
+	struct bin_attribute attr_eb;
+
 	/*
 	 * Only the first part of the SPA is used for the process element
 	 * linked list. The only other part that software needs to worry ab=

out

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@@ -563,6 +567,9 @@ static inline void __iomem *_cxl_p2n_addr(struct =

cxl_afu *afu, cxl_p2n_reg_t reg

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 u16 cxl_afu_cr_read16(struct cxl_afu *afu, int cr, u64 off);
 u8 cxl_afu_cr_read8(struct cxl_afu *afu, int cr, u64 off);
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+ssize_t cxl_afu_read_err_buffer(struct cxl_afu *afu, char *buf,
+				loff_t off, size_t count);
+
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 struct cxl_calls {
 	void (*cxl_slbia)(struct mm_struct *mm);

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 1ef0164..162a8fc 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c

@@ -593,6 +593,22 @@ static int cxl_read_afu_descriptor(struct cxl_af=

u *afu)

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 	afu->crs_len =3D AFUD_CR_LEN(val) * 256;
 	afu->crs_offset =3D AFUD_READ_CR_OFF(afu);
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+
+	/* eb_len is in multiple of 4K */
+	afu->eb_len =3D AFUD_EB_LEN(AFUD_READ_EB(afu)) * 4096;
+	afu->eb_offset =3D AFUD_READ_EB_OFF(afu);
+
+	/* eb_off is 4K aligned so lower 12 bits are always zero */
+	if (EXTRACT_PPC_BITS(afu->eb_offset, 0, 11) !=3D 0) {
+		dev_warn(&afu->dev,
+			 "Invalid AFU error buffer offset %Lx\n",
+			 afu->eb_offset);
+		dev_info(&afu->dev,
+			 "Ignoring AFU error buffer in the descriptor\n");
+		/* indicate that no afu buffer exists */
+		afu->eb_len =3D 0;
+	}
+
 	return 0;
 }
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@@ -672,6 +688,50 @@ static int sanitise_afu_regs(struct cxl_afu *afu=

)

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 	return 0;
 }
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+/*
+ * afu_eb_read:
+ * Called from sysfs and reads the afu error info buffer. The h/w on=

ly supports

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+ * 4/8 bytes aligned access. So most of the code tries to get around=

 this by

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+ * reading full 8 bytes aligned chunks, copying it to a temp buffer =

and dropping

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+ * unneeded bytes at the beginning & the end of the requested region=

.

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+ */
+ssize_t cxl_afu_read_err_buffer(struct cxl_afu *afu, char *buf,
+				loff_t off, size_t count)
+{
+	u8 tbuff[8];
+	const void __iomem *ebuf =3D afu->afu_desc_mmio + afu->eb_offset;
+
+	count =3D min((size_t)(afu->eb_len - off), count);
+
+	if (unlikely(count <=3D 0)) {
+		/* handle case where no ebuf exists or offset out of bound */
+		count =3D 0;
+
+	} else if ((count >=3D 8) && IS_ALIGNED(off, 8)) {
+		/* read all the intermediate aligned words */
+
+		count =3D round_down(off + count, 8) - off;
+		_memcpy_fromio(buf,
+			       ebuf + off, count);
+
+	} else if (!IS_ALIGNED(off, 8)) {
+		/* handle unaligned access at the beginning */
+		_memcpy_fromio(tbuff, ebuf + round_down(off, 8), 8);
+
+		count =3D min((size_t)(ALIGN(off, 8) - off), count);
+		memcpy(buf, tbuff + (off & 0x7), count);
+
+	} else {
+		/* offset is aligned but count < 8 */
+		_memcpy_fromio(tbuff, ebuf + round_down(off + count, 8), 8);
+
+		count =3D (off + count) - round_down(off + count, 8);
+		memcpy(buf, tbuff, count);
+	}

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I still think this is too complex.  How about something like this where
we always use a copy buffer (completely untested):
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        copy_size_max =3D PAGESIZE;
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        ebuf_start =3D round_down(off, 8);
        ebuf_length =3D min(count + 16, copy_size_max); // copy extra f=

or alignment at start and end

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        count =3D min(count, copy_size_max);  // Adjust for max copy
        length
        count =3D count - (off & 7); // Adjust for non aligned offset
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        tbuff =3D __get_free_page(GFP_KERNEL);
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        _memcpy_fromio(tbuff, ebuf_start, ebuf_length);
        memcpy(buf, tbuff + (off & 0x7), count); // grab what we need
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        free_page(tbuff);
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        return count;

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Slightly updated version as there was a bug in the count calculation.
Still untested.
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                copy_size_max =3D PAGESIZE;
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                ebuf_start =3D round_down(off, 8);
                ebuf_length =3D min(count + 16, copy_size_max); // copy e=

xtra for alignment at start and end

We can make these two lines even simpler to read:

  ebuf_start =3D round_down(off, 8);
  ebuf_end =3D round_up(off + count, 8);
  ebuf_length =3D min(ebuf_end - ebuf_start, copy_size_max);

                if ((count + (off & 7)) > copy_size_max)
                   /* adjust count if we go past copy_size_max */
                   count =3D copy_size_max - (off & 7);
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                tbuff =3D __get_free_page(GFP_KERNEL);
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                _memcpy_fromio(tbuff, ebuf_start, ebuf_length);
                memcpy(buf, tbuff + (off & 0x7), count); // grab what we =

need

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                free_page(tbuff);
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                return count;
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Mikey
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       =20
Mikey
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+
+	return count;
+}
+
 static int cxl_init_afu(struct cxl *adapter, int slice, struct pci_d=

ev *dev)

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 {
 	struct cxl_afu *afu;

diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
index d0c38c7..4942d55 100644
--- a/drivers/misc/cxl/sysfs.c
+++ b/drivers/misc/cxl/sysfs.c

@@ -356,6 +356,16 @@ static ssize_t api_version_compatible_show(struc=

t device *device,

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 	return scnprintf(buf, PAGE_SIZE, "%i\n", CXL_API_VERSION_COMPATIBLE=

);

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 }
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+static ssize_t afu_eb_read(struct file *filp, struct kobject *kobj,
+			       struct bin_attribute *bin_attr, char *buf,
+			       loff_t off, size_t count)
+{
+	struct cxl_afu *afu =3D to_cxl_afu(container_of(kobj,
+						      struct device, kobj));
+
+	return cxl_afu_read_err_buffer(afu, buf, off, count);
+}
+
 static struct device_attribute afu_attrs[] =3D {
 	__ATTR_RO(mmio_size),
 	__ATTR_RO(irqs_min),

@@ -534,6 +544,10 @@ void cxl_sysfs_afu_remove(struct cxl_afu *afu)
 	struct afu_config_record *cr, *tmp;
 	int i;

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+	/* remove the err buffer bin attribute */
+	if (afu->eb_len)
+		device_remove_bin_file(&afu->dev, &afu->attr_eb);
+
 	for (i =3D 0; i < ARRAY_SIZE(afu_attrs); i++)
 		device_remove_file(&afu->dev, &afu_attrs[i]);
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@@ -555,6 +569,22 @@ int cxl_sysfs_afu_add(struct cxl_afu *afu)
 			goto err;
 	}

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+	/* conditionally create the add the binary file for error info buff=

er */

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+	if (afu->eb_len) {
+		afu->attr_eb.attr.name =3D "afu_err_buff";
+		afu->attr_eb.attr.mode =3D S_IRUGO;
+		afu->attr_eb.size =3D afu->eb_len;
+		afu->attr_eb.read =3D afu_eb_read;
+
+		rc =3D device_create_bin_file(&afu->dev, &afu->attr_eb);
+		if (rc) {
+			dev_err(&afu->dev,
+				"Unable to create eb attr for the afu. Err(%d)\n",
+				rc);
+			goto err;
+		}
+	}
+
 	for (i =3D 0; i < afu->crs_num; i++) {
 		cr =3D cxl_sysfs_afu_new_cr(afu, i);
 		if (IS_ERR(cr)) {

@@ -570,6 +600,9 @@ err1:
 	cxl_sysfs_afu_remove(afu);
 	return rc;
 err:
+	/* reset the eb_len as we havent created the bin attr */
+	afu->eb_len =3D 0;
+
 	for (i--; i >=3D 0; i--)
 		device_remove_file(&afu->dev, &afu_attrs[i]);
 	return rc;

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