[PATCH 2/3] net: phy: realtek: Enable accessing RTL8211E extension pages

[Matthias Kaehlcke <mka@chromium.org>]

The RTL8211E has extension pages, which can be accessed after
selecting a page through a custom method. Add a function to
modify bits in a register of an extension page and a few
helpers for dealing with ext pages.

rtl8211e_modify_ext_paged() and rtl821e_restore_page() are
inspired by their counterparts phy_modify_paged() and
phy_restore_page().

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
---
This code might be applicable to other Realtek PHYs, but I don't
have access to the datasheets to confirm it, so for now it's just
for the RTL8211E.

 drivers/net/phy/realtek.c | 61 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index a669945eb829..dfc2e20ef335 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c
@@ -26,6 +26,9 @@
 #define RTL821x_EXT_PAGE_SELECT			0x1e
 #define RTL821x_PAGE_SELECT			0x1f
 
+#define RTL8211E_EXT_PAGE			7
+#define RTL8211E_EPAGSR				0x1e
+
 #define RTL8211F_INSR				0x1d
 
 #define RTL8211F_TX_DELAY			BIT(8)
@@ -53,6 +56,64 @@ static int rtl821x_write_page(struct phy_device *phydev, int page)
 	return __phy_write(phydev, RTL821x_PAGE_SELECT, page);
 }
 
+static int rtl821e_select_ext_page(struct phy_device *phydev, int page)
+{
+	int rc;
+
+	rc = phy_write(phydev, RTL821x_PAGE_SELECT, RTL8211E_EXT_PAGE);
+	if (rc)
+		return rc;
+
+	return phy_write(phydev, RTL8211E_EPAGSR, page);
+}
+
+static int rtl821e_restore_page(struct phy_device *phydev, int oldpage, int ret)
+{
+	int r;
+
+	if (oldpage >= 0) {
+		r = phy_write(phydev, RTL821x_PAGE_SELECT, oldpage);
+
+		/* Propagate the operation return code if the page write
+		 * was successful.
+		 */
+		if (ret >= 0 && r < 0)
+			ret = r;
+	} else {
+		/* Propagate the page selection error code */
+		ret = oldpage;
+	}
+
+	return ret;
+}
+
+static int __maybe_unused rtl8211e_modify_ext_paged(struct phy_device *phydev,
+				    int page, u32 regnum, u16 mask, u16 set)
+{
+	int ret = 0;
+	int oldpage;
+	int new;
+
+	oldpage = phy_read(phydev, RTL821x_PAGE_SELECT);
+	if (oldpage < 0)
+		goto out;
+
+	ret = rtl821e_select_ext_page(phydev, page);
+	if (ret)
+		goto out;
+
+	ret = phy_read(phydev, regnum);
+	if (ret < 0)
+		goto out;
+
+	new = (ret & ~mask) | set;
+	if (new != ret)
+		ret = phy_write(phydev, regnum, new);
+
+out:
+	return rtl821e_restore_page(phydev, oldpage, ret);
+}
+
 static int rtl8201_ack_interrupt(struct phy_device *phydev)
 {
 	int err;
-- 
2.22.0.410.gd8fdbe21b5-goog