On Mon, Apr 29, 2019 at 11:31:14AM +0000, Naga Sureshkumar Relli wrote:
> But just wanted to know, do you see issues with these __force and __iomem
> castings?
I only see a minor issue: They're (deliberately) lengthy. Using many of
them diverts attention of the reader. Therefore, my proposal attempted
to reduce their frequency. The only issue I see here is readability.
> >
> > > + u8 addr_cycles;
> > > + struct clk *mclk;
> >
> > All you need here is the memory clock frequency. Wouldn't it be easier to
> > extract that
> > frequency once during probe and store it here? That assumes a constant
> > frequency, but if the
> > frequency isn't constant, you have a race condition.
> That is what we are doing in the probe.
> In the probe, we are getting mclk using of_clk_get() and then we are getting
> the actual frequency
> Using clk_get_rate().
> And this is constant frequency only(getting from dts)
Not quite. You're getting a clock reference in probe and then repeatedly
access the frequency elswhere. I am suggesting that you get the clock
frequency during probe and never save the clock reference to a struct.
> > > + case NAND_OP_ADDR_INSTR:
> > > + offset = nand_subop_get_addr_start_off(subop, op_id);
> > > + naddrs = nand_subop_get_num_addr_cyc(subop, op_id);
> > > + addrs = &instr->ctx.addr.addrs[offset];
> > > + nfc_op->addrs = instr->ctx.addr.addrs[offset];
> > > + for (i = 0; i < min_t(unsigned int, 4, naddrs); i++) {
> > > + nfc_op->addrs |= instr->ctx.addr.addrs[i] <<
> >
> > I don't quite understand what this code does, but it looks strange to me. I
> > compared it to other
> > drivers. The code here is quite similar to marvell_nand.c. It seems like we
> > are copying a
> > varying number (0 to 6) of addresses from the buffer instr->ctx.addr.addrs.
> > However their
> > indices are special: 0, 1, 2, 3, offset + 4, offset + 5. This is
> > non-consecutive and different from
> > marvell_nand.c in this regard. Could it be that you really meant index
> > offset+i here?
> I didn't get, what you are saying here.
> It is about updating page and column addresses.
> Are you asking me to remove nfc_op->addrs = instr->ctx.addr.addrs[offset];
> before for loop?
I compared this code to marvell_nand.c and noticed a subtle difference.
Both snippets read 6 address bytes and consume them in a driver-specific
way. Now which address bytes are consumed differs.
marvell_nand.c consumes instr->ctx.addr.addrs at indices offset,
offset+1, offset+2, offset+3, offset+4, offset+5. pl353_nand.c consumes
instr->ctx.addr.addrs at indices 0, 1, 2, 3, offset, offset+4, offset+5.
(In my previous mail, I didn't notice that it was also consuming the
offset index.)
I would have expected this behaviour to be consistent between different
drivers. If I assume marvell_nand.c to do the right thing and
pl353_nand.c to be wrong (which is not necessarily a correct
assumption), then the code woule likely becom:
addrs = &instr->ctx.addr.addrs[offset];
for (i = 0; i < min_t(unsigned int, 4, naddrs); i++) {
nfc_op->addrs |= addrs[i] << (8 * i);
// ^^^^^
}
Hope this helps.
Helmut
