[PATCH] spufs: implement mfc access for PPE-side DMA

This patch adds a new file called 'mfc' to each spufs directory.
The file accepts DMA commands that are a subset of what would
be legal DMA commands for problem state register access. Upon
reading the file, a bitmask is returned with the completed
tag groups set.

The file is meant to be used from an abstraction in libspe
that is added by a different patch.

From the kernel perspective, this means a process can now
offload a memory copy from or into an SPE local store
without having to run code on the SPE itself.

The transfer will only be performed while the SPE is owned
by one thread that is waiting in the spu_run system call
and the data will be transferred into that thread's
address space, independent of which thread started the
transfer.

Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 294 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/cell/spufs/file.c b/arch/powerpc/platforms/cell/spufs/file.c
index dfa649c9b9566..62fe9941ccee2 100644
--- a/arch/powerpc/platforms/cell/spufs/file.c
+++ b/arch/powerpc/platforms/cell/spufs/file.c
@@ -20,6 +20,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+#undef DEBUG
+
 #include <linux/fs.h>
 #include <linux/ioctl.h>
 #include <linux/module.h>
@@ -641,6 +643,297 @@ static u64 spufs_signal2_type_get(void *data)
 DEFINE_SIMPLE_ATTRIBUTE(spufs_signal2_type, spufs_signal2_type_get,
 					spufs_signal2_type_set, "%llu");
 
+
+static int spufs_mfc_open(struct inode *inode, struct file *file)
+{
+	struct spufs_inode_info *i = SPUFS_I(inode);
+	struct spu_context *ctx = i->i_ctx;
+
+	/* we don't want to deal with DMA into other processes */
+	if (ctx->owner != current->mm)
+		return -EINVAL;
+
+	if (atomic_read(&inode->i_count) != 1)
+		return -EBUSY;
+
+	file->private_data = ctx;
+	return nonseekable_open(inode, file);
+}
+
+/* interrupt-level mfc callback function. */
+void spufs_mfc_callback(struct spu *spu)
+{
+	struct spu_context *ctx = spu->ctx;
+
+	wake_up_all(&ctx->mfc_wq);
+
+	pr_debug("%s %s\n", __FUNCTION__, spu->name);
+	if (ctx->mfc_fasync) {
+		u32 free_elements, tagstatus;
+		unsigned int mask;
+
+		/* no need for spu_acquire in interrupt context */
+		free_elements = ctx->ops->get_mfc_free_elements(ctx);
+		tagstatus = ctx->ops->read_mfc_tagstatus(ctx);
+
+		mask = 0;
+		if (free_elements & 0xffff)
+			mask |= POLLOUT;
+		if (tagstatus & ctx->tagwait)
+			mask |= POLLIN;
+
+		kill_fasync(&ctx->mfc_fasync, SIGIO, mask);
+	}
+}
+
+static int spufs_read_mfc_tagstatus(struct spu_context *ctx, u32 *status)
+{
+	/* See if there is one tag group is complete */
+	/* FIXME we need locking around tagwait */
+	*status = ctx->ops->read_mfc_tagstatus(ctx) & ctx->tagwait;
+	ctx->tagwait &= ~*status;
+	if (*status)
+		return 1;
+
+	/* enable interrupt waiting for any tag group,
+	   may silently fail if interrupts are already enabled */
+	ctx->ops->set_mfc_query(ctx, ctx->tagwait, 1);
+	return 0;
+}
+
+static ssize_t spufs_mfc_read(struct file *file, char __user *buffer,
+			size_t size, loff_t *pos)
+{
+	struct spu_context *ctx = file->private_data;
+	int ret = -EINVAL;
+	u32 status;
+
+	if (size != 4)
+		goto out;
+
+	spu_acquire(ctx);
+	if (file->f_flags & O_NONBLOCK) {
+		status = ctx->ops->read_mfc_tagstatus(ctx);
+		if (!(status & ctx->tagwait))
+			ret = -EAGAIN;
+		else
+			ctx->tagwait &= ~status;
+	} else {
+		ret = spufs_wait(ctx->mfc_wq,
+			   spufs_read_mfc_tagstatus(ctx, &status));
+	}
+	spu_release(ctx);
+
+	if (ret)
+		goto out;
+
+	ret = 4;
+	if (copy_to_user(buffer, &status, 4))
+		ret = -EFAULT;
+
+out:
+	return ret;
+}
+
+static int spufs_check_valid_dma(struct mfc_dma_command *cmd)
+{
+	pr_debug("queueing DMA %x %lx %x %x %x\n", cmd->lsa,
+		 cmd->ea, cmd->size, cmd->tag, cmd->cmd);
+
+	switch (cmd->cmd) {
+	case MFC_PUT_CMD:
+	case MFC_PUTF_CMD:
+	case MFC_PUTB_CMD:
+	case MFC_GET_CMD:
+	case MFC_GETF_CMD:
+	case MFC_GETB_CMD:
+		break;
+	default:
+		pr_debug("invalid DMA opcode %x\n", cmd->cmd);
+		return -EIO;
+	}
+
+	if ((cmd->lsa & 0xf) != (cmd->ea &0xf)) {
+		pr_debug("invalid DMA alignment, ea %lx lsa %x\n",
+				cmd->ea, cmd->lsa);
+		return -EIO;
+	}
+
+	switch (cmd->size & 0xf) {
+	case 1:
+		break;
+	case 2:
+		if (cmd->lsa & 1)
+			goto error;
+		break;
+	case 4:
+		if (cmd->lsa & 3)
+			goto error;
+		break;
+	case 8:
+		if (cmd->lsa & 7)
+			goto error;
+		break;
+	case 0:
+		if (cmd->lsa & 15)
+			goto error;
+		break;
+	error:
+	default:
+		pr_debug("invalid DMA alignment %x for size %x\n",
+			cmd->lsa & 0xf, cmd->size);
+		return -EIO;
+	}
+
+	if (cmd->size > 16 * 1024) {
+		pr_debug("invalid DMA size %x\n", cmd->size);
+		return -EIO;
+	}
+
+	if (cmd->tag & 0xfff0) {
+		/* we reserve the higher tag numbers for kernel use */
+		pr_debug("invalid DMA tag\n");
+		return -EIO;
+	}
+
+	if (cmd->class) {
+		/* not supported in this version */
+		pr_debug("invalid DMA class\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int spu_send_mfc_command(struct spu_context *ctx,
+				struct mfc_dma_command cmd,
+				int *error)
+{
+	*error = ctx->ops->send_mfc_command(ctx, &cmd);
+	if (*error == -EAGAIN) {
+		/* wait for any tag group to complete
+		   so we have space for the new command */
+		ctx->ops->set_mfc_query(ctx, ctx->tagwait, 1);
+		/* try again, because the queue might be
+		   empty again */
+		*error = ctx->ops->send_mfc_command(ctx, &cmd);
+		if (*error == -EAGAIN)
+			return 0;
+	}
+	return 1;
+}
+
+static ssize_t spufs_mfc_write(struct file *file, const char __user *buffer,
+			size_t size, loff_t *pos)
+{
+	struct spu_context *ctx = file->private_data;
+	struct mfc_dma_command cmd;
+	int ret = -EINVAL;
+
+	if (size != sizeof cmd)
+		goto out;
+
+	ret = -EFAULT;
+	if (copy_from_user(&cmd, buffer, sizeof cmd))
+		goto out;
+
+	ret = spufs_check_valid_dma(&cmd);
+	if (ret)
+		goto out;
+
+	spu_acquire_runnable(ctx);
+	if (file->f_flags & O_NONBLOCK) {
+		ret = ctx->ops->send_mfc_command(ctx, &cmd);
+	} else {
+		int status;
+		ret = spufs_wait(ctx->mfc_wq,
+				 spu_send_mfc_command(ctx, cmd, &status));
+		if (status)
+			ret = status;
+	}
+	spu_release(ctx);
+
+	if (ret)
+		goto out;
+
+	ctx->tagwait |= 1 << cmd.tag;
+
+out:
+	return ret;
+}
+
+static unsigned int spufs_mfc_poll(struct file *file,poll_table *wait)
+{
+	struct spu_context *ctx = file->private_data;
+	u32 free_elements, tagstatus;
+	unsigned int mask;
+
+	spu_acquire(ctx);
+	ctx->ops->set_mfc_query(ctx, ctx->tagwait, 2);
+	free_elements = ctx->ops->get_mfc_free_elements(ctx);
+	tagstatus = ctx->ops->read_mfc_tagstatus(ctx);
+	spu_release(ctx);
+
+	poll_wait(file, &ctx->mfc_wq, wait);
+
+	mask = 0;
+	if (free_elements & 0xffff)
+		mask |= POLLOUT | POLLWRNORM;
+	if (tagstatus & ctx->tagwait)
+		mask |= POLLIN | POLLRDNORM;
+
+	pr_debug("%s: free %d tagstatus %d tagwait %d\n", __FUNCTION__,
+		free_elements, tagstatus, ctx->tagwait);
+
+	return mask;
+}
+
+static int spufs_mfc_flush(struct file *file)
+{
+	struct spu_context *ctx = file->private_data;
+	int ret;
+
+	spu_acquire(ctx);
+#if 0
+/* this currently hangs */
+	ret = spufs_wait(ctx->mfc_wq,
+			 ctx->ops->set_mfc_query(ctx, ctx->tagwait, 2));
+	if (ret)
+		goto out;
+	ret = spufs_wait(ctx->mfc_wq,
+			 ctx->ops->read_mfc_tagstatus(ctx) == ctx->tagwait);
+out:
+#else
+	ret = 0;
+#endif
+	spu_release(ctx);
+
+	return ret;
+}
+
+static int spufs_mfc_fsync(struct file *file, struct dentry *dentry,
+			   int datasync)
+{
+	return spufs_mfc_flush(file);
+}
+
+static int spufs_mfc_fasync(int fd, struct file *file, int on)
+{
+	struct spu_context *ctx = file->private_data;
+
+	return fasync_helper(fd, file, on, &ctx->mfc_fasync);
+}
+
+static struct file_operations spufs_mfc_fops = {
+	.open	 = spufs_mfc_open,
+	.read	 = spufs_mfc_read,
+	.write	 = spufs_mfc_write,
+	.poll	 = spufs_mfc_poll,
+	.flush	 = spufs_mfc_flush,
+	.fsync	 = spufs_mfc_fsync,
+	.fasync	 = spufs_mfc_fasync,
+};
+
 static void spufs_npc_set(void *data, u64 val)
 {
 	struct spu_context *ctx = data;
@@ -783,6 +1076,7 @@ struct tree_descr spufs_dir_contents[] = {
 	{ "signal2", &spufs_signal2_fops, 0666, },
 	{ "signal1_type", &spufs_signal1_type, 0666, },
 	{ "signal2_type", &spufs_signal2_type, 0666, },
+	{ "mfc", &spufs_mfc_fops, 0666, },
 	{ "npc", &spufs_npc_ops, 0666, },
 	{ "fpcr", &spufs_fpcr_fops, 0666, },
 	{ "decr", &spufs_decr_ops, 0666, },