Re: [PATCH] phy: realtek: use new helpers for paged register access

Am 12.01.2018 um 22:01 schrieb Andrew Lunn:

On Fri, Jan 12, 2018 at 09:30:08PM +0100, Heiner Kallweit wrote:

quoted

Make use of the new helpers for paged register access.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/net/phy/realtek.c | 59 +++++++++++------------------------------------
 1 file changed, 14 insertions(+), 45 deletions(-)

diff --git a/drivers/net/phy/realtek.c b/drivers/net/phy/realtek.c
index 7c1bf688d..887bad07a 100644
--- a/drivers/net/phy/realtek.c
+++ b/drivers/net/phy/realtek.c

@@ -41,37 +41,14 @@ MODULE_DESCRIPTION("Realtek PHY driver");
 MODULE_AUTHOR("Johnson Leung");
 MODULE_LICENSE("GPL");
 
-static int rtl8211x_page_read(struct phy_device *phydev, u16 page, u16 address)
+static int rtl821x_read_page(struct phy_device *phydev)
 {
-	int ret;
-
-	ret = phy_write(phydev, RTL821x_PAGE_SELECT, page);
-	if (ret)
-		return ret;
-
-	ret = phy_read(phydev, address);
-
-	/* restore to default page 0 */
-	phy_write(phydev, RTL821x_PAGE_SELECT, 0x0);
-
-	return ret;
+	return phy_read(phydev, RTL821x_PAGE_SELECT);

Hi Heiner

It think this is wrong. You need to use __phy_read(). phy_read() does
an mdiobus_read(), which takes the bus->mdio_lock. However,

Uh, you are of course right.

int phy_save_page(struct phy_device *phydev)
{
        mutex_lock(&phydev->mdio.bus->mdio_lock);
        return __phy_read_page(phydev);
}

This also takes the same lock. So this should deadlock.

Try turning on CONFIG_PROVE_LOCKING, it will detect problems like
this.

Thanks for the hint. I have this option set, however my test system
doesn't use the irq-related callbacks. So it wasn't able to report
the issue. My fault.

	Andrew