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Message-ID: <CACoXjck-=q9SBoFrLufs0GbrEcHN0jrHNmKLJ9Uf2-5MnhMD2Q@mail.gmail.com>
Date: Mon, 21 May 2012 09:48:08 +0530
From: Tanmay Inamdar <tinamdar@....com>
To: Josh Boyer <jwboyer@...il.com>
Cc: benh@...nel.crashing.org, grant.likely@...retlab.ca,
linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
devicetree-discuss@...ts.ozlabs.org
Subject: Re: [V2 5/5] powerpc: kernel: 16650 UART reg-shift support
On Wed, May 9, 2012 at 10:57 AM, Tanmay Inamdar <tinamdar@....com> wrote:
> On Wed, May 2, 2012 at 7:08 PM, Josh Boyer <jwboyer@...il.com> wrote:
>> On Mon, Apr 9, 2012 at 3:20 AM, Tanmay Inamdar <tinamdar@....com> wrote:
>>> In APM8018X SOC, UART register address space has been relocated to 32-bit
>>> data boundaries for APB bus implementation.
>>> Current legacy_serial driver ignores the reg-shift property. This patch
>>> modifies legacy_serial.c and udbg_16550.c to work with above mentioned UARTs.
>>>
>>> Signed-off-by: Tanmay Inamdar <tinamdar@....com>
>>> ---
>>> :100644 100644 8338aef... f5fc106... M arch/powerpc/include/asm/udbg.h
>>> :100644 100644 bedd12e... d523b7d... M arch/powerpc/kernel/legacy_serial.c
>>> :100644 100644 6837f83... e0cb7dc... M arch/powerpc/kernel/udbg_16550.c
>>> arch/powerpc/include/asm/udbg.h | 2 +-
>>> arch/powerpc/kernel/legacy_serial.c | 16 +++++---
>>> arch/powerpc/kernel/udbg_16550.c | 64 ++++++++++++++++++++++------------
>>> 3 files changed, 52 insertions(+), 30 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/udbg.h b/arch/powerpc/include/asm/udbg.h
>>> index 8338aef..f5fc106 100644
>>> --- a/arch/powerpc/include/asm/udbg.h
>>> +++ b/arch/powerpc/include/asm/udbg.h
>>> @@ -29,7 +29,7 @@ extern void udbg_printf(const char *fmt, ...)
>>> extern void udbg_progress(char *s, unsigned short hex);
>>>
>>> extern void udbg_init_uart(void __iomem *comport, unsigned int speed,
>>> - unsigned int clock);
>>> + unsigned int clock, unsigned int regshift);
>>> extern unsigned int udbg_probe_uart_speed(void __iomem *comport,
>>> unsigned int clock);
>>>
>>> diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
>>> index bedd12e..d523b7d 100644
>>> --- a/arch/powerpc/kernel/legacy_serial.c
>>> +++ b/arch/powerpc/kernel/legacy_serial.c
>>> @@ -33,6 +33,7 @@ static struct legacy_serial_info {
>>> unsigned int clock;
>>> int irq_check_parent;
>>> phys_addr_t taddr;
>>> + unsigned int regshift;
>>> } legacy_serial_infos[MAX_LEGACY_SERIAL_PORTS];
>>>
>>> static struct __initdata of_device_id legacy_serial_parents[] = {
>>> @@ -42,6 +43,7 @@ static struct __initdata of_device_id legacy_serial_parents[] = {
>>> {.compatible = "ibm,opb",},
>>> {.compatible = "simple-bus",},
>>> {.compatible = "wrs,epld-localbus",},
>>> + {.compatible = "apm,apb",},
>>> {},
>>> };
>>>
>>> @@ -163,11 +165,6 @@ static int __init add_legacy_soc_port(struct device_node *np,
>>> if (of_get_property(np, "clock-frequency", NULL) == NULL)
>>> return -1;
>>>
>>> - /* if reg-shift or offset, don't try to use it */
>>> - if ((of_get_property(np, "reg-shift", NULL) != NULL) ||
>>> - (of_get_property(np, "reg-offset", NULL) != NULL))
>>> - return -1;
>>> -
>>
>> So we explicitly didn't support reg-shift before. I'm guessing there is
>> a reason for that, but I don't recall what. Ben?
>>
>> Also, why do you need to use the legacy serial driver at all for this
>> SOC? As far as I remember, the OF serial driver should be sufficient.
>>
>
> You are right. There is no need to use legacy serial driver. However I
> realized that when 40x is selected, 'PPC_UDBG_16550' is by default
> selected. This enables legacy serial driver.
>
> Is it now required to enable 'PPC_UDBG_16550' by default for every SOC
> that uses 40x processor?
>
Josh, Ben,
Please let me know if you have any comments regarding above question.
>>> +static unsigned int reg_shift;
>>> +#define ns16550_offset(addr) (addr - (unsigned char *)udbg_comport)
>>> +
>>> static struct NS16550 __iomem *udbg_comport;
>>>
>>> +static inline u8 serial_read(unsigned char *addr)
>>> +{
>>> + u32 offset = ns16550_offset(addr) << reg_shift;
>>> + return readb(udbg_comport + offset);
>>> +}
>>> +
>>> +static inline void serial_write(unsigned char *addr, char val)
>>> +{
>>> + u32 offset = ns16550_offset(addr) << reg_shift;
>>> + writeb(val, udbg_comport + offset);
>>> +}
>>> +
>>
>> I don't think readb/writeb are correct here. Why did you switch to
>> using those instead of sticking with in_8/out_8?
>>
>> josh
>
> Thanks,
> Tanmay
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