On 03/05/2015 03:54 PM, Andy Shevchenko wrote:
On Thu, 2015-03-05 at 14:41 -0600, Thor Thayer wrote:
Hi Andy,
On 03/05/2015 04:43 AM, Andy Shevchenko wrote:
On Wed, 2015-03-04 at 16:01 -0600, Thor Thayer wrote:
Hi Andy,
On 03/04/2015 02:44 PM, Andy Shevchenko wrote:
On Wed, 2015-03-04 at 14:31 -0600, ttha...@opensource.altera.com wrote:
From: Thor Thayer <ttha...@opensource.altera.com>
The Altera Arria10 SoC requires 32 bit accesses to peripherals. The
DesignWare SPI peripheral registers are on 32bit boundaries so this
patch is minimal. Function pointers are used to select 32bit access
or 16bit accesses.
So, what is exactly the issue when we read only half of the register?
Bus lock, or what?
The read actually works on our chip but I changed both read and write to
be consistent. For Arria10, on a 16 bit write the data isn't written
into the DesignWare register.
How did you exactly check this?
Sorry, I should have been more clear. The architecture of the Arria10
SoC enforces 32 bit writes - even for the APB bus. The Arria10's
interconnect only allows 32 bit writes.
Hmm… So, reads are okay, but writes are 32 bit only? Have you any link
to the documentation where I could read this?
Currently Table 7-6 in the Arria10 Technical Reference Manual [1] on
page 141 shows SPI Master as a 32 bit wide interface but it doesn't
explicitly note the 32bit write requirement. We're adding a note to
table 7-6 as a result of this discussion.
[1] http://www.altera.com/literature/hb/arria-10/a10_5v4.pdf
As a result, the solution below doesn't work for us.
My thought was about post writes. That's why I was wondering and still
wonder if something to clarify in the documentation.
I do have a much cleaner patch to re-submit but I haven't applied it on
top of your patches yet & tested yet.
Okay, please, apply the above as a part of commit message.
I also would like to test it on Intel Medfield.
In reply to your other email, yes it does support the DW_apb_ssi but the
Arria10 architecture requires 32 bit access (actually as you point out,
32 bit writes). We're using the original driver on our older chips but
Arria10 requires upstream changes.
Can you check if the following helps in your case:
--- a/drivers/spi/spi-dw.h
+++ b/drivers/spi/spi-dw.h
@@ -170,6 +170,8 @@ static inline u16 dw_readw(struct dw_spi *dws, u32 offset)
static inline void dw_writew(struct dw_spi *dws, u32 offset, u16 val)
{
__raw_writew(val, dws->regs + offset);
+ mmiowb():
+ __raw_readw(dws->regs + offset);
}
static inline void spi_enable_chip(struct dw_spi *dws, int enable)
--
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