Messages in this thread | | | From | Grant Likely <> | Date | Thu, 7 Feb 2013 15:23:16 +0000 | Subject | Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be) |
| |
On Thu, Feb 7, 2013 at 3:12 PM, Alexey Brodkin <Alexey.Brodkin@synopsys.com> wrote: > On 02/07/2013 06:51 PM, Grant Likely wrote: >> >> On Thu, Feb 7, 2013 at 2:39 PM, Grant Likely <grant.likely@secretlab.ca> >> wrote: >>> >>> On Wed, Feb 6, 2013 at 9:35 PM, Benjamin Herrenschmidt >>> <benh@kernel.crashing.org> wrote: >>>>> >>>>> In fact, the driver already knows about this and figures >>>>> out at runtime how the device is wired up to the bus. This is not the >>>>> problem. >>>> >>>> >>>> Except that this is very gross, especially when you observe that in the >>>> busted "big endian" case, it has to byteswap the bloody data port. >>>> >>>> So you end up having to do that gross hack with separate accessors for >>>> registers vs. data and not able to use the _rep variants, which also >>>> means that on platforms like ppc, you end up with a memory barrier on >>>> every access (or more), which is going to slow things down enormously. >>> >>> >>> I don't see why the _rep variants aren't usable here. The only reason >>> I didn't use them when I wrote the driver in the first place was I was >>> a n00b kernel hacker and I didn't know they were there. >> >> >> The 8-bit variant is different though because the hardware requires >> pingponging between odd and even byte addresses to flush the fifo. >> Reading a data port even address (0x40) gives the least significant >> byte. Reading from an odd address (0x41) give the MSB and pops the >> data off the FIFO. So, yes, the _rep variant can't be used in 8-bit >> mode. It should still be fine in 16-bit. >> >> page 45: http://www.xilinx.com/support/documentation/data_sheets/ds080.pdf >> > > Ok, so may I do a re-spin with these changes:
There are two things here. 1) changing the accessors used. 2) switching the endianess as a bug fix. Any changes to the endian access should be a separate patch which a description of what is needed.
> 1. In "ace_in_be16" use "ioread16be" > 2. In "ace_out_be16" use "iowrite16be" > 3. In "ace_in_le16" use "ioread16" > 4. In "ace_out_le16" use "iowrite16"
Yes
> 5. In "ace_datain_le16" use "ioread16_rep" > 6. In "ace_dataout_le16" use "iowrite16_rep"
Maybe. In a separate patch. Hmmm... I guess there isn't an ioread16be_rep variant. Oh well. Check first with Michal on LE microblaze before making the change. If it doesn't work for him the more understanding is needed. I was pretty sure the LE variant already worked.
> not sure about items for "ace_datain/out_be16" - what about _rep options > here?
ioread16_rep should be fine. The ace_data{in,out}_be16 routines need to use the LE accessor. The existing code is definitely correct in this respect.
g.
| |