Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16with generic iowrite(read)8/16(be)

From: Michal Simek
Date: Tue Feb 12 2013 - 12:03:08 EST

2013/2/7 Grant Likely <grant.likely@xxxxxxxxxxxx>:
> On Thu, Feb 7, 2013 at 3:12 PM, Alexey Brodkin
> <Alexey.Brodkin@xxxxxxxxxxxx> wrote:
>> On 02/07/2013 06:51 PM, Grant Likely wrote:
>>> On Thu, Feb 7, 2013 at 2:39 PM, Grant Likely <grant.likely@xxxxxxxxxxxx>
>>> wrote:
>>>> On Wed, Feb 6, 2013 at 9:35 PM, Benjamin Herrenschmidt
>>>> <benh@xxxxxxxxxxxxxxxxxxx> 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:
>> 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.

Sorry it took me some time to get 16bit LE to work for test but here
are test results.

I have tested it on ppc BE, Microblaze BE and Microblaze LE systems
and surprisingly on all of them only ace_reg_le16_ops are used.

But on Microblaze LE is necessary to use different datain/out_le16
functions as below
which are also not compatible with Microblaze and PPC BE.

diff --git a/drivers/block/xsysace.c b/drivers/block/xsysace.c
index bbad046..8dd192c 100644
--- a/drivers/block/xsysace.c
+++ b/drivers/block/xsysace.c
@@ -314,7 +314,7 @@ static void ace_datain_le16(struct ace_device *ace)
int i = ACE_FIFO_SIZE / 2;
u16 *dst = ace->data_ptr;
while (i--)
- *dst++ = ioread16be(ace->baseaddr + 0x40);
+ *dst++ = ioread16(ace->baseaddr + 0x40);
ace->data_ptr = dst;

@@ -323,7 +323,7 @@ static void ace_dataout_le16(struct ace_device *ace)
int i = ACE_FIFO_SIZE / 2;
u16 *src = ace->data_ptr;
while (i--)
- iowrite16be(*src++, ace->baseaddr + 0x40);
+ iowrite16(*src++, ace->baseaddr + 0x40);
ace->data_ptr = src;

Grant: How did you tested BE mode? It is fpga it means you can switch
some connections
and it could work.


Michal Simek, Ing. (M.Eng)
w: p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu -
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at