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

From: Karunika Choo
Date: Fri Apr 11 2025 - 11:22:13 EST

On 10/04/2025 17:46, Boris Brezillon wrote:
> On Thu, 10 Apr 2025 17:35:46 +0100
> Karunika Choo <karunika.choo@xxxxxxx> 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.
>>
>> This patch also updates Panthor to use the new 64-bit accessors and poll
>> functions.
>>
>> Signed-off-by: Karunika Choo <karunika.choo@xxxxxxx>
>> ---
>> drivers/gpu/drm/panthor/panthor_device.h | 71 ++++++++++++
>> drivers/gpu/drm/panthor/panthor_fw.c | 9 +-
>> drivers/gpu/drm/panthor/panthor_gpu.c | 142 ++++++-----------------
>> drivers/gpu/drm/panthor/panthor_mmu.c | 34 ++----
>> drivers/gpu/drm/panthor/panthor_regs.h | 6 -
>> 5 files changed, 124 insertions(+), 138 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
>> index da6574021664..5028e25f5e0d 100644
>> --- a/drivers/gpu/drm/panthor/panthor_device.h
>> +++ b/drivers/gpu/drm/panthor/panthor_device.h
>> @@ -428,4 +428,75 @@ static int panthor_request_ ## __name ## _irq(struct panthor_device *ptdev, \
>>
>> extern struct workqueue_struct *panthor_cleanup_wq;
>>
>> +static inline void gpu_write(struct panthor_device *ptdev, u32 reg, u32 data)
>> +{
>> + writel(data, ptdev->iomem + reg);
>> +}
>> +
>> +static inline u32 gpu_read(struct panthor_device *ptdev, u32 reg)
>> +{
>> + return readl(ptdev->iomem + reg);
>> +}
>> +
>> +static inline u32 gpu_read_relaxed(struct panthor_device *ptdev, u32 reg)
>> +{
>> + return readl_relaxed(ptdev->iomem + reg);
>> +}
>> +
>> +static inline void gpu_write64(struct panthor_device *ptdev, u32 reg, u64 data)
>> +{
>> + gpu_write(ptdev, reg, lower_32_bits(data));
>> + gpu_write(ptdev, reg + 4, upper_32_bits(data));
>> +}
>> +
>> +static inline u64 gpu_read64(struct panthor_device *ptdev, u32 reg)
>> +{
>> + return (gpu_read(ptdev, reg) | ((u64)gpu_read(ptdev, reg + 4) << 32));
>> +}
>> +
>> +static inline u64 gpu_read64_relaxed(struct panthor_device *ptdev, u32 reg)
>> +{
>> + return (gpu_read_relaxed(ptdev, reg) |
>> + ((u64)gpu_read_relaxed(ptdev, reg + 4) << 32));
>> +}
>> +
>> +static inline u64 gpu_read64_counter(struct panthor_device *ptdev, u32 reg)
>> +{
>> + u32 lo, hi1, hi2;
>> + do {
>> + hi1 = gpu_read(ptdev, reg + 4);
>> + lo = gpu_read(ptdev, reg);
>> + hi2 = gpu_read(ptdev, reg + 4);
>> + } while (hi1 != hi2);
>> + return lo | ((u64)hi2 << 32);
>> +}
>> +
>> +#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)
>
> nit: can use use tabs to pad till the '\' at the end of the line so we
> can have a consistent formatting across these definitions?
>
>> +
>> +#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
>> diff --git a/drivers/gpu/drm/panthor/panthor_fw.c b/drivers/gpu/drm/panthor/panthor_fw.c
>> index 0f52766a3120..ecfbe0456f89 100644
>> --- a/drivers/gpu/drm/panthor/panthor_fw.c
>> +++ b/drivers/gpu/drm/panthor/panthor_fw.c
>> @@ -1059,8 +1059,8 @@ static void panthor_fw_stop(struct panthor_device *ptdev)
>> u32 status;
>>
>> gpu_write(ptdev, MCU_CONTROL, MCU_CONTROL_DISABLE);
>> - if (readl_poll_timeout(ptdev->iomem + MCU_STATUS, status,
>> - status == MCU_STATUS_DISABLED, 10, 100000))
>> + if (gpu_read_poll_timeout(ptdev, MCU_STATUS, status,
>> + status == MCU_STATUS_DISABLED, 10, 100000))
>> drm_err(&ptdev->base, "Failed to stop MCU");
>> }
>>
>> @@ -1085,8 +1085,9 @@ void panthor_fw_pre_reset(struct panthor_device *ptdev, bool on_hang)
>>
>> panthor_fw_update_reqs(glb_iface, req, GLB_HALT, GLB_HALT);
>> gpu_write(ptdev, CSF_DOORBELL(CSF_GLB_DOORBELL_ID), 1);
>> - if (!readl_poll_timeout(ptdev->iomem + MCU_STATUS, status,
>> - status == MCU_STATUS_HALT, 10, 100000)) {
>> + if (!gpu_read_poll_timeout(ptdev, MCU_STATUS, status,
>> + status == MCU_STATUS_HALT, 10,
>> + 100000)) {
>> ptdev->reset.fast = true;
>> } else {
>> drm_warn(&ptdev->base, "Failed to cleanly suspend MCU");
>> diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c
>> index 671049020afa..fd09f0928019 100644
>> --- a/drivers/gpu/drm/panthor/panthor_gpu.c
>> +++ b/drivers/gpu/drm/panthor/panthor_gpu.c
>> @@ -108,14 +108,9 @@ static void panthor_gpu_init_info(struct panthor_device *ptdev)
>>
>> ptdev->gpu_info.as_present = gpu_read(ptdev, GPU_AS_PRESENT);
>>
>> - ptdev->gpu_info.shader_present = gpu_read(ptdev, GPU_SHADER_PRESENT_LO);
>> - ptdev->gpu_info.shader_present |= (u64)gpu_read(ptdev, GPU_SHADER_PRESENT_HI) << 32;
>> -
>> - ptdev->gpu_info.tiler_present = gpu_read(ptdev, GPU_TILER_PRESENT_LO);
>> - ptdev->gpu_info.tiler_present |= (u64)gpu_read(ptdev, GPU_TILER_PRESENT_HI) << 32;
>> -
>> - ptdev->gpu_info.l2_present = gpu_read(ptdev, GPU_L2_PRESENT_LO);
>> - ptdev->gpu_info.l2_present |= (u64)gpu_read(ptdev, GPU_L2_PRESENT_HI) << 32;
>> + ptdev->gpu_info.shader_present = gpu_read64(ptdev, GPU_SHADER_PRESENT_LO);
>> + ptdev->gpu_info.tiler_present = gpu_read64(ptdev, GPU_TILER_PRESENT_LO);
>> + ptdev->gpu_info.l2_present = gpu_read64(ptdev, GPU_L2_PRESENT_LO);
>
> Now that we have proper 64-bit accessors, I think I would drop the
> _LO/_HI definitions and just go a single def per register that replaces
> the _LO one.

Hello,

please find a link to v2 below that addresses your comments.

- https://lore.kernel.org/dri-devel/20250411151140.1815435-1-karunika.choo@xxxxxxx/

Kind regards,
Karunika Choo