Re: [PATCH] net: phy: broadcom: add support for BCM5221 phy

Hello Florian,

thanks for reviewing,

On 12/08/23 01:52, Florian Fainelli wrote:

On 8/11/2023 2:53 PM, Giulio Benetti wrote:

quoted

This patch adds the BCM5221 PHY support by reusing
brcm_fet_config_intr() and brcm_fet_handle_interrupt() and
implementing config_init()/suspend()/resume().

Sponsored by: Tekvox Inc.
Cc: Jim Reinhart <redacted>
Cc: James Autry <redacted>
Cc: Matthew Maron <redacted>
Signed-off-by: Giulio Benetti <giulio.benetti@benettiengineering.com>

Looks good, few comments below.

quoted

---
  drivers/net/phy/broadcom.c | 144 +++++++++++++++++++++++++++++++++++++
  include/linux/brcmphy.h    |   8 +++
  2 files changed, 152 insertions(+)

diff --git a/drivers/net/phy/broadcom.c b/drivers/net/phy/broadcom.c
index 59cae0d808aa..99f6c0485f01 100644
--- a/drivers/net/phy/broadcom.c
+++ b/drivers/net/phy/broadcom.c

@@ -754,6 +754,84 @@ static int brcm_fet_config_init(struct phy_device *phydev)

      return err;
  }
+static int bcm5221_config_init(struct phy_device *phydev)
+{

Very similar to brcm_fet_config_init() except that you configure fewer interrupt sources, do not have the LED mode programming and your MDI-X programming is done via a 10BaseT specific register rather than the shadow.

Can you consider adding parameters to brcm_fet_config_init() such that you can specify the 5221 specific settings such as the interrupt mask for instance?

So if I've understood correctly I should drop bcm5221_config_init() and
use brcm_fet_config_init() by checking the struct phy_driver .phy_id to
be PHY_ID_BCM5221.

This should help address the locking that Russell suggested.

But I don't understand how this can help to prevent the locking Russell
suggested, can you please elaborate more or point me and example?
As far as I've understood I should take care to lock sections to prevent
from interrupts to occur during shadow mode switching, is it correct?
So maybe you mean that if I do this in brcm_fet_config_init() it will be
fixed for the other phys using brcm_fet_config_init(), correct?

[snip]

quoted

+static int bcm5221_suspend(struct phy_device *phydev)
+{
+    int reg, err, err2, brcmtest;
+
+    /* Enable shadow register access */
+    brcmtest = phy_read(phydev, MII_BRCM_FET_BRCMTEST);
+    if (brcmtest < 0)
+        return brcmtest;
+
+    reg = brcmtest | MII_BRCM_FET_BT_SRE;
+
+    err = phy_write(phydev, MII_BRCM_FET_BRCMTEST, reg);
+    if (err < 0)
+        return err;
+
+    /* Force Low Power Mode with clock enabled */
+    err = phy_set_bits(phydev, MII_BRCM_FET_SHDW_AUXMODE4,
+               BCM5221_SHDW_AM4_EN_CLK_LPM |
+               BCM5221_SHDW_AM4_FORCE_LPM);
+
+    /* Disable shadow register access */
+    err2 = phy_write(phydev, MII_BRCM_FET_BRCMTEST, brcmtest);
+    if (!err)
+        err = err2;
+
+    return err;
+}

bcm5221_suspend() is essentially brcm_fet_suspend() minus the setting of the BMCR.PDOWN bit, can you consider factoring brcm_fet_suspend() into a helper that can decide whether to set the power down bit or not? Does not brcm_fet_suspend() work as-is?

Sure, I will,

quoted

+
+static int bcm5221_resume(struct phy_device *phydev)
+{

This should really be calling bcm5221_config_init() here, if the PHY was on a power island that is powered off during system suspend, bcm5221_resume() would not be restoring the auto-power down that is set during config_init(), probably not desired because that means you will burn power when the cable is disconnected...

oh yes! You're right, I will then drop bcm5221_resume() in favor of bcm5221_config_init(), so brcm_fet_config_init() with phy_id == PHY_ID_BCM5221 checks.

Thanks again
Best regards
-- 
Giulio Benetti
CEO&CTO@Benetti Engineering sas