net: phy: add paged PHY register accessors

Synchronize paged PHY helpers with Linux v6.17.

Add support for PHY devices that use paged register access by
implementing the following functions:
- phy_save_page(): Save current page number
- phy_select_page(): Switch to a specific page and return previous page
- phy_restore_page(): Restore previously saved page

Also adds read_page and write_page callbacks to the phy_driver
structure to enable driver-specific page handling.

These helpers allow safe access to paged PHY registers by ensuring
proper page selection and restoration,
even in error conditions, which will be used by the Airoha PHY driver.

Signed-off-by: Lucien.Jheng <lucienzx159@gmail.com>

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 9702d0422962db706d777c7949b17dc9426089e1..b58283fe3d5f2f8c6dd22283677d68e2fa5cb1e5 100644 (file)
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -1250,3 +1250,116 @@ bool phy_interface_is_ncsi(void)
        return 0;
 #endif
 }
+
+/**
+ * __phy_read_page() - read the current page
+ * @phydev: a pointer to a &struct phy_device
+ *
+ * Returns page index or < 0 on error
+ */
+static int __phy_read_page(struct phy_device *phydev)
+{
+       struct phy_driver *drv = phydev->drv;
+
+       if (!drv->read_page) {
+               debug("read_page callback not available, PHY driver not loaded?\n");
+               return -EOPNOTSUPP;
+       }
+
+       return drv->read_page(phydev);
+}
+
+/**
+ * __phy_write_page() - Write a new page
+ * @phydev: a pointer to a &struct phy_device
+ * @page: page index to select
+ *
+ * Returns 0 or < 0 on error.
+ */
+static int __phy_write_page(struct phy_device *phydev, int page)
+{
+       struct phy_driver *drv = phydev->drv;
+
+       if (!drv->write_page) {
+               debug("write_page callback not available, PHY driver not loaded?\n");
+               return -EOPNOTSUPP;
+       }
+
+       return drv->write_page(phydev, page);
+}
+
+/**
+ * phy_save_page() - save the current page
+ * @phydev: a pointer to a &struct phy_device
+ *
+ * Return the current page number. On error,
+ * returns a negative errno. phy_restore_page() must always be called
+ * after this, irrespective of success or failure of this call.
+ */
+int phy_save_page(struct phy_device *phydev)
+{
+       return __phy_read_page(phydev);
+}
+
+/**
+ * phy_select_page - Switch to a PHY page and return the previous page
+ * @phydev: a pointer to a &struct phy_device
+ * @page: desired page
+ *
+ * NOTE: Save the current PHY page, and set the current page.
+ * On error, returns a negative errno, otherwise returns the previous page number.
+ * phy_restore_page() must always be called after this, irrespective
+ * of success or failure of this call.
+ */
+int phy_select_page(struct phy_device *phydev, int page)
+{
+       int ret, oldpage;
+
+       oldpage = ret = phy_save_page(phydev);
+       if (ret < 0)
+               return ret;
+
+       if (oldpage != page) {
+               ret = __phy_write_page(phydev, page);
+               if (ret < 0)
+                       return ret;
+       }
+
+       return oldpage;
+}
+
+/**
+ * phy_restore_page - Restore a previously saved page and propagate status
+ * @phydev: a pointer to a &struct phy_device
+ * @oldpage: the old page, return value from phy_save_page() or phy_select_page()
+ * @ret: operation's return code
+ *
+ * Restoring @oldpage if it is a valid page.
+ * This function propagates the earliest error code from the group of
+ * operations.
+ *
+ * Returns:
+ *   @oldpage if it was a negative value, otherwise
+ *   @ret if it was a negative errno value, otherwise
+ *   phy_write_page()'s negative value if it were in error, otherwise
+ *   @ret.
+ */
+int phy_restore_page(struct phy_device *phydev, int oldpage, int ret)
+{
+       int r;
+
+       if (oldpage >= 0) {
+               r = __phy_write_page(phydev, oldpage);
+
+               /* Propagate the operation return code if the page write
+                * was successful.
+                */
+               if (ret >= 0 && r < 0)
+                       ret = r;
+       } else {
+               /* Propagate the phy page selection error code */
+               ret = oldpage;
+       }
+
+       return ret;
+}
\ No newline at end of file

diff --git a/include/phy.h b/include/phy.h
index 36354aaf774a3b17b923fc93391e4f2ffbe94aa4..ae9fd1652cccd5e54be4c83364bdaa0a8558c4e6 100644 (file)
--- a/include/phy.h
+++ b/include/phy.h
@@ -123,6 +123,11 @@ struct phy_driver {
        int (*write_mmd)(struct phy_device *phydev, int devad, int reg,
                         u16 val);
 
+       /** @read_page: Return the current PHY register page number */
+       int (*read_page)(struct phy_device *phydev);
+       /** @write_page: Set the current PHY register page number */
+       int (*write_page)(struct phy_device *phydev, int page);
+
        /* driver private data */
        ulong data;
 };
@@ -314,6 +319,9 @@ int phy_modify_mmd_changed(struct phy_device *phydev, int devad, u32 regnum,
                           u16 mask, u16 set);
 int phy_modify_mmd(struct phy_device *phydev, int devad, u32 regnum,
                   u16 mask, u16 set);
+int phy_save_page(struct phy_device *phydev);
+int phy_select_page(struct phy_device *phydev, int page);
+int phy_restore_page(struct phy_device *phydev, int oldpage, int ret);
 
 int phy_startup(struct phy_device *phydev);
 int phy_config(struct phy_device *phydev);