Re: [PATCH v2 1/9] drm/panthor: Add 64-bit and poll register accessors

Karunika Choo
2025-04-09T13:01:11Z

On 21/03/2025 07:48, Boris Brezillon wrote:
> On Thu, 20 Mar 2025 11:17:33 +0000
> Karunika Choo <karunika.choo@arm.com> wrote:
>
>> This patch adds 64-bit register accessors to simplify register access in
>> Panthor. It also adds 32-bit and 64-bit variants for read_poll_timeout.
>>
>> Signed-off-by: Karunika Choo <karunika.choo@arm.com>
>> ---
>> drivers/gpu/drm/panthor/panthor_regs.h | 55 ++++++++++++++++++++++++++
>> 1 file changed, 55 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_regs.h
b/drivers/gpu/drm/panthor/panthor_regs.h
>> index 42dc3fedb0d4..7ec4a1d04e20 100644
>> --- a/drivers/gpu/drm/panthor/panthor_regs.h
>> +++ b/drivers/gpu/drm/panthor/panthor_regs.h
>> @@ -238,4 +238,59 @@
>> #define gpu_read(dev, reg) \
>> readl((dev)->iomem + (reg))
>>
>> +#define gpu_read_relaxed(dev, reg) readl_relaxed((dev)->iomem + (reg))
>> +
>> +#define gpu_write64(dev, reg, data) \
>> + do { \
>> + u64 __val = (u64)(data); \
>> + gpu_write(dev, reg, lower_32_bits(__val)); \
>> + gpu_write(dev, reg + 4, upper_32_bits(__val)); \
>> + } while (0)
>
> We're not doing funky name concatenation in these macros, so I'd rather
> have them defined as static inline funcs in panthor_device.h. We
> probably want to move the gpu_read/write definitions there as well if
> we do that.

I see where you're coming from, and it makes sense. I was thinking it
might be better to keep it in panthor_regs.h since that's the file we
include when accessing GPU registers. That said, we could certainly
convert them to static inline functions if you prefer.

>> +
>> +#define gpu_read64(dev, reg) \
>> + (gpu_read(dev, reg) | ((u64)gpu_read(dev, reg + 4) << 32))
>> +
>> +#define gpu_read64_relaxed(dev, reg) \
>> + (gpu_read_relaxed(dev, reg) | \
>> + ((u64)gpu_read_relaxed(dev, reg + 4) << 32))
>> +
>> +#define gpu_read64_sync(dev, reg) \
>> + ({ \
>> + u32 lo, hi1, hi2; \
>> + do { \
>> + hi1 = gpu_read(dev, reg + 4); \
>> + lo = gpu_read(dev, reg); \
>> + hi2 = gpu_read(dev, reg + 4); \
>> + } while (hi1 != hi2); \
>> + lo | ((u64)hi2 << 32); \
>> + })
>
> I would name that one gpu_read64_counter and make it a static inline
> function. Note that we already have panthor_gpu_read_64bit_counter()
> which does the same thing, so maybe move it there and rename it along
> the way.

Happy to rename this to gpu_read64_counter in v3, if you're okay with
us keeping the macros/functions in this file.

Kind regards,
Karunika

>> +
>> +#define gpu_read_poll_timeout(dev, reg, val, cond, delay_us,
timeout_us) \
>> + read_poll_timeout(gpu_read, val, cond, delay_us, timeout_us, false, \
>> + dev, reg)
>> +
>> +#define gpu_read_poll_timeout_atomic(dev, reg, val, cond, delay_us,
\
>> + timeout_us) \
>> + read_poll_timeout_atomic(gpu_read, val, cond, delay_us, timeout_us, \
>> + false, dev, reg)
>> +
>> +#define gpu_read64_poll_timeout(dev, reg, val, cond, delay_us,
timeout_us) \
>> + read_poll_timeout(gpu_read64, val, cond, delay_us, timeout_us, false, \
>> + dev, reg)
>> +
>> +#define gpu_read64_poll_timeout_atomic(dev, reg, val, cond,
delay_us, \
>> + timeout_us) \
>> + read_poll_timeout_atomic(gpu_read64, val, cond, delay_us, timeout_us, \
>> + false, dev, reg)
>> +
>> +#define gpu_read_relaxed_poll_timeout_atomic(dev, reg, val, cond,
delay_us, \
>> + timeout_us) \
>> + read_poll_timeout_atomic(gpu_read_relaxed, val, cond, delay_us, \
>> + timeout_us, false, dev, reg)
>> +
>> +#define gpu_read64_relaxed_poll_timeout(dev, reg, val, cond,
delay_us, \
>> + timeout_us) \
>> + read_poll_timeout(gpu_read64_relaxed, val, cond, delay_us,
timeout_us, \
>> + false, dev, reg)
>> +
>> #endif
>