netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 195 insertions, 0 deletions

diff --git a/drivers/gpu/host1x/mipi.c b/drivers/gpu/host1x/mipi.c
new file mode 100644
index 000000000..988681423
--- /dev/null
+++ b/drivers/gpu/host1x/mipi.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2013 NVIDIA Corporation
+ * Copyright (C) 2025 Svyatoslav Ryhel <clamor95@gmail.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/tegra-mipi-cal.h>
+
+/* only need to support one provider */
+static struct {
+	struct device_node *np;
+	const struct tegra_mipi_ops *ops;
+} provider;
+
+/**
+ * tegra_mipi_enable - Enable the Tegra MIPI calibration device.
+ * @device: Handle to the Tegra MIPI calibration device.
+ *
+ * This calls the enable sequence for the Tegra MIPI calibration device.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int tegra_mipi_enable(struct tegra_mipi_device *device)
+{
+	if (device->ops->enable)
+		return device->ops->enable(device);
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_mipi_enable);
+
+/**
+ * tegra_mipi_disable - Disable the Tegra MIPI calibration device.
+ * @device: Handle to the Tegra MIPI calibration device.
+ *
+ * This calls the disable sequence for the Tegra MIPI calibration device.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int tegra_mipi_disable(struct tegra_mipi_device *device)
+{
+	if (device->ops->disable)
+		return device->ops->disable(device);
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_mipi_disable);
+
+/**
+ * tegra_mipi_start_calibration - Start the Tegra MIPI calibration sequence.
+ * @device: Handle to the Tegra MIPI calibration device.
+ *
+ * This initiates the calibration of CSI/DSI interfaces via the Tegra MIPI
+ * calibration device.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int tegra_mipi_start_calibration(struct tegra_mipi_device *device)
+{
+	if (device->ops->start_calibration)
+		return device->ops->start_calibration(device);
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_mipi_start_calibration);
+
+/**
+ * tegra_mipi_finish_calibration - Finish the Tegra MIPI calibration sequence.
+ * @device: Handle to the Tegra MIPI calibration device.
+ *
+ * This completes the calibration of CSI/DSI interfaces via the Tegra MIPI
+ * calibration device.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int tegra_mipi_finish_calibration(struct tegra_mipi_device *device)
+{
+	if (device->ops->finish_calibration)
+		return device->ops->finish_calibration(device);
+
+	return 0;
+}
+EXPORT_SYMBOL(tegra_mipi_finish_calibration);
+
+/**
+ * tegra_mipi_request - Request a Tegra MIPI calibration device.
+ * @device: Handle of the device requesting the MIPI calibration function.
+ * @np: Device node pointer of the device requesting the MIPI calibration
+ *	function.
+ *
+ * This function requests a reference to a Tegra MIPI calibration device.
+ *
+ * Returns a pointer to the Tegra MIPI calibration device on success,
+ * or an ERR_PTR-encoded error code on failure.
+ */
+struct tegra_mipi_device *tegra_mipi_request(struct device *device,
+					     struct device_node *np)
+{
+	struct tegra_mipi_device *mipidev;
+	struct of_phandle_args args;
+	int err;
+
+	err = of_parse_phandle_with_args(np, "nvidia,mipi-calibrate",
+					 "#nvidia,mipi-calibrate-cells", 0,
+					 &args);
+	if (err < 0)
+		return ERR_PTR(err);
+
+	if (provider.np != args.np) {
+		err = -ENODEV;
+		goto out;
+	}
+
+	mipidev = kzalloc_obj(*mipidev);
+	if (!mipidev) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	mipidev->pdev = of_find_device_by_node(args.np);
+	if (!mipidev->pdev) {
+		err = -ENODEV;
+		goto free;
+	}
+
+	of_node_put(args.np);
+
+	mipidev->ops = provider.ops;
+	mipidev->pads = args.args[0];
+
+	return mipidev;
+
+free:
+	kfree(mipidev);
+out:
+	of_node_put(args.np);
+	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(tegra_mipi_request);
+
+/**
+ * tegra_mipi_free - Free a Tegra MIPI calibration device.
+ * @mipidev: Handle to the Tegra MIPI calibration device.
+ *
+ * This function releases a reference to a Tegra MIPI calibration device
+ * previously requested by tegra_mipi_request().
+ */
+void tegra_mipi_free(struct tegra_mipi_device *mipidev)
+{
+	platform_device_put(mipidev->pdev);
+	kfree(mipidev);
+}
+EXPORT_SYMBOL(tegra_mipi_free);
+
+static void tegra_mipi_remove_provider(void *data)
+{
+	provider.np = NULL;
+	provider.ops = NULL;
+}
+
+/**
+ * devm_tegra_mipi_add_provider - Managed registration of a Tegra MIPI
+ *				  calibration function provider.
+ * @device: Handle to the device providing the MIPI calibration function.
+ * @np: Device node pointer of the device providing the MIPI calibration
+ *	function.
+ * @ops: Operations supported by the MIPI calibration device.
+ *
+ * This registers a device that provides MIPI calibration functions.
+ * For Tegra20 and Tegra30, this is the CSI block, while Tegra114 and
+ * newer SoC generations have a dedicated hardware block for these
+ * functions.
+ *
+ * Returns 0 on success or a negative error code on failure.
+ */
+int devm_tegra_mipi_add_provider(struct device *device, struct device_node *np,
+				 const struct tegra_mipi_ops *ops)
+{
+	if (provider.np)
+		return -EBUSY;
+
+	provider.np = np;
+	provider.ops = ops;
+
+	return devm_add_action_or_reset(device, tegra_mipi_remove_provider, NULL);
+}
+EXPORT_SYMBOL(devm_tegra_mipi_add_provider);