Hi Simon,
On 20.04.2016 17:09, Simon Glass wrote:
Hi Stefan,
On 20 April 2016 at 08:58, Stefan Roese <s...@denx.de> wrote:
Hi Simon.
On 20.04.2016 16:40, Simon Glass wrote:
On 11 April 2016 at 09:03, Stefan Roese <s...@denx.de> wrote:
Hi Simon,
On 04.04.2016 16:53, Stefan Roese wrote:
Hi Simon,
as you seem to be back from vacation (?), we (Bin and myself) would
like to hear your expert comment on a x86 issue I've discovered
while porting the Designware I2C driver to x86. Please see below:
On 28.03.2016 08:01, Bin Meng wrote:
Hi Stefan,
On Mon, Mar 21, 2016 at 10:04 PM, Stefan Roese <s...@denx.de> wrote:
Hi Bin,
On 21.03.2016 13:43, Bin Meng wrote:
On Mon, Mar 21, 2016 at 8:04 PM, Stefan Roese <s...@denx.de> wrote:
Hi Bin,
On 21.03.2016 10:03, Stefan Roese wrote:
<snip>
static int designware_i2c_probe_chip(struct udevice *bus,
uint chip_addr,
@@ -476,14 +519,45 @@ static int designware_i2c_probe(struct
udevice *bus)
{
struct dw_i2c *priv = dev_get_priv(bus);
+#ifdef CONFIG_X86
+ /* Save base address from PCI BAR */
+ priv->regs = (struct i2c_regs *)
+ dm_pci_map_bar(bus, PCI_BASE_ADDRESS_0,
PCI_REGION_MEM);
+ /* Use BayTrail specific timing values */
+ priv->scl_sda_cfg = &byt_config;
+#else
How about:
if (device_is_on_pci_bus(dev)) {
do the PCI I2C stuff here;
}
I've tried this but it generated compilation errors on socfpga, as
the
dm_pci_xxx functions are not available there. So it definitely needs
some #ifdef here. I could go with your suggestion and use
#if CONFIG_DM_PCI as well.
See driver/net/designware.c for example.
/* Save base address from device-tree */
priv->regs = (struct i2c_regs *)dev_get_addr(bus);
+#endif
Enabling this code for x86 via if (device_is_on_pci_bus(dev)) results
in this ugly compilation warning:
drivers/i2c/designware_i2c.c: In function ‘designware_i2c_probe’:
drivers/i2c/designware_i2c.c:530:16: warning: cast to pointer from
integer of different size [-Wint-to-pointer-cast]
priv->regs = (struct i2c_regs *)dev_get_addr(bus);
^
This is because x86 defines fdt_addr_t / phys_addr_t as 64bit. So
I'm wondering, how dev_get_addr() should get used on x86. Has it
been used anywhere here at all? Should we perhaps go back to
a 32bit phy_addr representation again? So that dev_get_addr()
matches the (void *) size again?
dev_get_addr() is being used on x86 drivers. See
ns16550_serial_ofdata_to_platdata() for example. There is no build
warning for the ns16550 driver.
Looking closer, the warning does not occur here, since the registers
are stored in a u32 variable "base". And assigning a 64bit value to a
32bit variable as in "plat->base = addr" in ns16550.c does not cause any
warnings.
Here in the I2C driver though, the base address is stored as a pointer
(pointer size is 32 bit for x86). And this triggers this warning, even
though its effectively the same assignment. I could cast to u32 but this
would cause problems on 64 bit architectures using this driver (in the
future). So I came up with this approach:
Thanks for digging out these.
/*
* On x86, "fdt_addr_t" is 64bit but "void *" only 32bit. So assigning
the
* register base directly in dev_get_addr() results in this
compilation warning:
* warning: cast to pointer from integer of different size
*
* Using this macro POINTER_SIZE_CAST, allows us to cast the result of
* dev_get_addr() into a 32bit value before casting it to the pointer
* (struct i2c_regs *).
*/
#ifdef CONFIG_X86
#define POINTER_SIZE_CAST u32
#endif
...
static int designware_i2c_probe(struct udevice *bus)
{
struct dw_i2c *priv = dev_get_priv(bus);
if (device_is_on_pci_bus(bus)) {
#ifdef CONFIG_DM_PCI
/* Save base address from PCI BAR */
priv->regs = (struct i2c_regs *)
dm_pci_map_bar(bus, PCI_BASE_ADDRESS_0,
PCI_REGION_MEM);
#ifdef CONFIG_X86
/* Use BayTrail specific timing values */
priv->scl_sda_cfg = &byt_config;
#endif
#endif
} else {
/* Save base address from device-tree */
priv->regs = (struct i2c_regs
*)(POINTER_SIZE_CAST)dev_get_addr(bus);
}
But I'm not 100% happy with this approach.
Yes, it's annoying.
So what are the alternatives:
a) Don't compile the dev_get_addr() part for x86 similar to what I've
done in v1
b) This approach with POINTER_SIZE_CAST
Any preferences of other ideas?
Side note: My general feeling is, that dev_get_addr() should be able to
get cast into a pointer on all platforms. This is how it is used in many
drivers, btw. Since this is not possible on x86, we might have a problem
here. Simon might have some ideas on this as well...
I would like to hear Simon's input. Simon?
Yes, Simon, what do you think?
Please also see my v2 of this patch which uses (__UINTPTR_TYPE__)
for the cast:
https://patchwork.ozlabs.org/patch/601113/
Simon, could you please take a quick look at this patch? With the
general problem of dev_get_addr() on x86 (as described above). Do you
have some other suggestions to solve this? Or is the solution in
v2 which uses (__UINTPTR_TYPE__) acceptable?
https://patchwork.ozlabs.org/patch/601113/
I feel that you should store the return value from dev_get_addr() in
an fdt_addr_t or a ulong. Then it can be cast to a pointer as you
wish. Platform data should hold the ulong, and private data
(dev_get_priv()) should hold the pointer.
I'm not keen on the POINTER_SIZE_CAST idea.
Does that fix the problem?
Yes, it does. In a somewhat less ugly way. This is my current result:
} else {
ulong base;
/* Save base address from device-tree */
/*
* On x86, "fdt_addr_t" is 64bit but "void *" only 32bit.
* So assigning the register base directly in dev_get_addr()
* results in this compilation warning:
* warning: cast to pointer from integer of different size
*
* Using an intermediate "ulong" variable before assigning
* this pointer to the "regs" variable solves this issue.
*/
base = dev_get_addr(bus);
priv->regs = (struct i2c_regs *)base;
}
If you think this is acceptable, I'll send a new patch version to
the list.
Seems fine to me. Perhaps we should have dev_get_addr_ptr() to do
this for us?
Might make sense. I can generate a small patch for this.
Perhaps we should better use "uintptr_t" as type for the intermediate
variable instead. But then we can effectively drop the intermediate
variable and do the casting directly.
What do you think?
Thanks,
Stefan
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