Messages in this thread | | | Date | Wed, 8 Mar 2023 01:33:54 +0200 | From | Vladimir Oltean <> | Subject | Re: [PATCH net 2/2] net: dsa: mt7530: set PLL frequency only when trgmii is used |
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On Wed, Mar 08, 2023 at 01:03:28AM +0300, arinc9.unal@gmail.com wrote: > From: Arınç ÜNAL <arinc.unal@arinc9.com> > > As my testing on the MCM MT7530 switch on MT7621 SoC shows, setting the PLL > frequency does not affect MII modes other than trgmii on port 5 and port 6. > So the assumption is that the operation here called "setting the PLL > frequency" actually sets the frequency of the TRGMII TX clock. > > Make it so that it is set only when the trgmii mode is used. > > Fixes: b8f126a8d543 ("net-next: dsa: add dsa support for Mediatek MT7530 switch") > Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com> > --- > drivers/net/dsa/mt7530.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c > index b1a79460df0e..961306c1ac14 100644 > --- a/drivers/net/dsa/mt7530.c > +++ b/drivers/net/dsa/mt7530.c > @@ -430,8 +430,6 @@ mt7530_pad_clk_setup(struct dsa_switch *ds, phy_interface_t interface) > switch (interface) { > case PHY_INTERFACE_MODE_RGMII: > trgint = 0; > - /* PLL frequency: 125MHz */ > - ncpo1 = 0x0c80; > break; > case PHY_INTERFACE_MODE_TRGMII: > trgint = 1; > -- > 2.37.2 >
NACK.
By deleting the assignment to the ncpo1 variable, it becomes uninitialized when port 6's interface mode is PHY_INTERFACE_MODE_RGMII. In the C language, uninitialized variables take the value of whatever memory happens to be on the stack at the address they are placed, interpreted as an appropriate data type for that variable - here u32.
Writing the value to CORE_PLL_GROUP5 happens when the function below is called, not when the "ncpo1" variable is assigned.
core_write(priv, CORE_PLL_GROUP5, RG_LCDDS_PCW_NCPO1(ncpo1));
It is not a good idea to write uninitialized kernel stack memory to hardware registers, unless perhaps you want to use it as some sort of poor quality entropy source for a random number generator...
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