Hi Geert,
thanks for the review - largely uncontroversial except for the volatile...
Am 14.03.2018 um 20:49 schrieb Geert Uytterhoeven:
>> +/* Blizzard 1230 DMA interface */
>> +
>> +struct blz1230_dma_registers {
>> + volatile unsigned char dma_addr; /* DMA address [0x0000]
>> */
>
> volatile considered harmful.
Yes, I saw that. I also saw gcc miscompile the DMA set-up (in
particular, the case where three bytes of the transfer address are
stuffed consecutively into the same DMA address register).
> If you would use proper *{read,write}*() accessors instead of direct
> assignments,
> you can drop the volatile's here.
Meaning writeb(val, reg) instead of reg = val?
#define out_8(addr,b) (void)((*(__force volatile u8 *) (addr)) = (b))
nicely hides the 'volatile' but suggests I also need to pass it a
pointer, so
writeb((addr >> 24) & 0xff, &dregs->dma_addr)
would do the same as
dregs->dma_addr = (addr >> 24) & 0xff; ??
I'll have to compare the assembly generated by the two versions before I
dare test that, but I'll give that a try. Liberal use of wmb() did fix
the miscompile but that just looked too ugly.
>> +#define ZORRO_ESP_PIO_LOOP(operands, reg1) \
>> + { \
>> + asm volatile ( \
>> + "1: moveb " operands "\n" \
>> + " subqw #1,%1 \n" \
>> + " jbne 1b \n" \
>> + : "+a" (addr), "+r" (reg1) \
>> + : "a" (fifo)); \
>> + }
>
> Please pass "addr" and "fifo" as macro parameters, too, so it's easier for
> the reviewer to notice they are used.
Yes, I can do that (meaning Finn would need to make the same change to
keep our versions in sync).
>> + /* Switch to the correct the DMA routine and clock frequency. */
>> + switch (ent->id) {
>> + case ZORRO_PROD_PHASE5_BLIZZARD_2060:
>> + zorro_esp_ops.send_dma_cmd = zorro_esp_send_blz2060_dma_cmd;
>
> Please use function pointers in struct zorro_driver_data, so you don't need
> a switch() here (except for Fastlane vs. B1230II).
At that point, the Blizzard 1230 II zorro_driver_data has been replaced
by the Fastlane one so the correct function pointer would be used. I
didn't realize that also nicely solves my problem here.
Thanks!
Cheers,
Michael
