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.
val = YYYY_SET(val, 0x1); /* set bit 1 - assuming YYYY set
bit 1 only */
val = ZZZZ_SET(val, 0x5); /* set upper 16 bit of the
register to 0x5 - assuming ZZZZ set field of the upper 16 bits */
Instead writing the above, I am replacing the above 4 lines with these
two lines:
cmd = CFG_IND_WR_CMD_MASK | CFG_IND_CMD_DONE_MASK;
cmd = CFG_IND_ADDR_SET(cmd, addr);
Is there clear?
-Loc
Cheers
Kishon
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