Marcelo Tosatti wrote:
On Mon, Aug 29, 2005 at 11:39:02PM -0400, Jeff Garzik wrote:
Marcelo Tosatti wrote:
+static int voltage_set(int slot, int vcc, int vpp)
+{
+ u_int reg = 0;
+
+ switch(vcc) {
+ case 0: break;
+ case 33:
+ reg |= BCSR1_PCVCTL4;
+ break;
+ case 50:
+ reg |= BCSR1_PCVCTL5;
+ break;
+ default:
+ return 1;
+ }
+
+ switch(vpp) {
+ case 0: break;
+ case 33:
+ case 50:
+ if(vcc == vpp)
+ reg |= BCSR1_PCVCTL6;
+ else
+ return 1;
+ break;
+ case 120:
+ reg |= BCSR1_PCVCTL7;
+ default:
+ return 1;
+ }
+
+ if(!((vcc == 50) || (vcc == 0)))
+ return 1;
+
+ /* first, turn off all power */
+
+ *((uint *)RPX_CSR_ADDR) &= ~(BCSR1_PCVCTL4 | BCSR1_PCVCTL5
+ | BCSR1_PCVCTL6 | BCSR1_PCVCTL7);
+
+ /* enable new powersettings */
+
+ *((uint *)RPX_CSR_ADDR) |= reg;
Should use bus read/write functions, such as foo_readl() or iowrite32().
The memory map structure which contains device configuration/registers
is _always_ directly mapped with pte's (the 8xx is a chip with builtin
UART/network/etc functionality).
I don't think there is a need to use read/write acessors.
There are multiple reasons:
* Easier reviewing. One cannot easily distinguish between writing to
normal kernel virtual memory and "magic" memory that produces magicaly
side effects such as initiating DMA of a net packet.
* Compiler safety. As the code is written now, you have no guarantees
that the compiler won't combine two stores to the same location, etc.
Accessor macros are a convenient place to add compiler barriers or
'volatile' notations that the MPC8xx code lacks.
* Maintainable. foo_read[bwl] or foo_read{8,16,32} are preferred
because that's the way other bus accessors look like -- yes even
embedded SoC buses benefit from these code patterns. You want your
driver to look like other drivers as much as possible.
* Convenience. The accessors can be a zero overhead memory read/write
at a minimum. But they can also be convenient places to use special
memory read/write instructions that specify uncached memop, compiler
barriers, memory barriers, etc.
Regards,
Jeff
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