Re: [PATCH RESEND v10 3/4] PHY: add APM X-Gene SoC 15Gbps Multi-purpose PHY driver

[Kishon Vijay Abraham I]

On Thursday 27 February 2014 12:04 PM, Kishon Vijay Abraham I wrote:
> On Thursday 27 February 2014 11:55 AM, Loc Ho wrote:
> > Hi,
> >
> > > > > > +
> > > > > > +static void sds_wr(void __iomem *csr_base, u32 indirect_cmd_reg,
> > > > > > +                  u32 indirect_data_reg, u32 addr, u32 data)
> > > > > > +{
> > > > > > +       u32 val;
> > > > > > +       u32 cmd;
> > > > > > +
> > > > > > +       cmd = CFG_IND_WR_CMD_MASK | CFG_IND_CMD_DONE_MASK;
> > > > > > +       cmd = CFG_IND_ADDR_SET(cmd, addr);
> > > > >
> > > > >
> > > > >
> > > > > This looks hacky. If 'CFG_IND_WR_CMD_MASK | CFG_IND_CMD_DONE_MASK'
> > > > > should
> > > > > be set then it should be part of the second argument. From the macro
> > > > > 'CFG_IND_ADDR_SET' the first argument should be more like the
> > > > > current value
> > > > > present in the register right? I feel the macro (CFG_IND_ADDR_SET)
> > > > > is not
> > > > > used in the way it is intended to.
> > > >
> > > >
> > > > The macro XXX_SET is intended to update an field within the register.
> > > > The update field is returned. The first assignment lines are setting
> > > > another field. Those two lines can be written as:
> > > >
> > > > cmd = 0;
> > > > cmd |= CFG_IND_WR_CMD_MASK;            ==> Set the CMD bit
> > > > cmd |= CFG_IND_CMD_DONE_MASK;        ==> Set the DONE bit
> > > > cmd = CFG_IND_ADDR_SET(cmd, addr);    ===> Set the field ADDR
> > >
> > >
> > > #define  CFG_IND_ADDR_SET(dst, src) \
> > >                  (((dst) & ~0x003ffff0) | (((u32)(src)<<4) &
> > > 0x003ffff0))
> > >
> > >  From this macro the first argument should be the present value in that
> > > register. Here you reset the address bits and write the new address
> > > bits.
> >
> > Yes.. This is correct. I am clearing x number of bit and then set new
> > value.
> >
> > > IMO the first argument should be the value in 'csr_base +
> > > indirect_cmd_reg'.
> > > So it resets the address bits in 'csr_base + indirect_cmd_reg' and write
> > > down the new address bits.
> >
> > Yes.. The above code does just that. In addition, I am also setting
> > the bits CFG_IND_WR_CMD_MASK and CFG_IND_CMD_DONE_MASK with the two
> > previous statement. Think of the code flow as follow:
> >
> > val = readl(some void * address); /* read the register */
>
> Where are you reading the register in your code (before CFG_IND_ADDR_SET)?
> > val = XXXX_SET(val, 0x1);            /* set bit 0  - assuming XXXX set
> > bit 0 only */
> If you want to set other bits (other than address) don't use
> CFG_IND_ADDR_SET macro. That looks hacky to me.

huh.. looked it again and I think only the readl is missing. If you can 
add that, it should be fine.

How about something like this

val = readl(csr_base + indirect_cmd_reg);
val = CFG_IND_ADDR_SET(val, addr);
val |= CFG_IND_WR_CMD_MASK | CFG_IND_CMD_DONE_MASK;
writel(val, csr_base + indirect_cmd_reg);

Cheers
Kishon
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