On 09/01/2010 02:37 PM, Marc Kleine-Budde wrote:
> Wolfgang Grandegger wrote:
>> On 09/01/2010 02:10 PM, Marc Kleine-Budde wrote:
>>> Wolfgang Grandegger wrote:
>>>>> static u16 spear1310_can_read_reg(const struct bosch_ccan_priv *priv,
>>>>> enum ccan_regs reg)
>>>>> {
>>>>> u16 val;
>>>>>
>>>>> /* 16 bit registers are aligned at 16-bit boundary */
>>>>> val = readw(priv->reg_base + reg);
>>>>> return val;
>>>>> }
>>>>>
>>>>> static void spear1310_can_write_reg(const struct bosch_ccan_priv *priv,
>>>>> enum ccan_regs reg, u16 val)
>>>>> {
>>>>> /* 16 bit registers are aligned at 16-bit boundary */
>>>>> writew(val, priv->reg_base + reg);
>>>>> }
>>>>>
>>>>> The one for SPEAr320 will look like:
>>>>> static u16 spear320_can_read_reg(const struct bosch_ccan_priv *priv,
>>>>> enum ccan_regs reg)
>>>>> {
>>>>> u16 val;
>>>>>
>>>>> /* shifting 1 place because 16 bit registers are word aligned */
>>>>> val = readw(priv->reg_base + (reg << 1));
>>>>> return val;
>>>>> }
>>>>>
>>>>> static void spear320_can_write_reg(const struct bosch_ccan_priv *priv,
>>>>> enum ccan_regs reg, u16 val)
>>>>> {
>>>>> /* shifting 1 place because 16 bit registers are word aligned */
>>>>> writew(val, priv->reg_base + (reg << 1));
>>>>> }
>>>> These functions are still pretty generic and could be handled by a
>>>> generic platform C_CAN driver via platform data field "reg_shift".
>>> the sja1000 uses IORESOURCE_MEM_xxBIT for this. See [1].
>>>
>>> cheers, Marc
>>>
>>> [1]
>>> http://lxr.linux.no/linux+v2.6.35/drivers/net/can/sja1000/sja1000_platform.c#L119
>>
>> Well, yes and no. I think for the SPEAr *word* accesses are required on
>> a 2 and 4 byte boundary? Bhupesh? We could use IORESOURCE_MEM_16BIT and
>> IORESOURCE_MEM_32BIT for these access types. But that might need to be
>> extended. In the C_CAN manual there is written:
>>
>> "Up to now the C_CAN module is delivered with three different
>> interfaces. An 8-bit interface for the Motorola HC08 controller and
>> two 16-bit interfaces to the AMBA APB bus from ARM. They can easily
>> be replaced by a user-defined module interface."
>
> We can do a regshift of 1 and a full 32 bit access even with
> IORESOURCE_MEM_16BIT, at least for now. Does 16 bit access work, too?
I don't understand!? So far I have only seen 16 bit accesses
(readw/writew) in Bhupesh's driver.
Wolfgang.
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