Re: [PATCH] drm/amdgpu: replace mutex with spin_lock

["Christian König" <ckoenig.leichtzumerken-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Keep in mind that under SRIOV you can read registers while in atomic 
context, e.g. while holding a spinlock.

Please double check if that won't bite us.

Apart from that the change looks good to me,
Christian.

Am 30.05.2018 um 12:19 schrieb Shirish S:
> mutex's lead to sleeps which should be avoided in
> atomic context.
> Hence this patch replaces it with the spin_locks.
>
> Signed-off-by: Shirish S <shirish.s@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c | 2 +-
>   drivers/gpu/drm/amd/amdgpu/atom.c            | 4 ++--
>   drivers/gpu/drm/amd/amdgpu/atom.h            | 3 ++-
>   3 files changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> index bf872f6..ba3d4b9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
> @@ -2033,7 +2033,7 @@ int amdgpu_atombios_init(struct amdgpu_device *adev)
>   		return -ENOMEM;
>   	}
>   
> -	mutex_init(&adev->mode_info.atom_context->mutex);
> +	spin_lock_init(&adev->mode_info.atom_context->lock);
>   	if (adev->is_atom_fw) {
>   		amdgpu_atomfirmware_scratch_regs_init(adev);
>   		amdgpu_atomfirmware_allocate_fb_scratch(adev);
> diff --git a/drivers/gpu/drm/amd/amdgpu/atom.c b/drivers/gpu/drm/amd/amdgpu/atom.c
> index 69500a8..bfd98f0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/atom.c
> +++ b/drivers/gpu/drm/amd/amdgpu/atom.c
> @@ -1261,7 +1261,7 @@ int amdgpu_atom_execute_table(struct atom_context *ctx, int index, uint32_t * pa
>   {
>   	int r;
>   
> -	mutex_lock(&ctx->mutex);
> +	spin_lock(&ctx->lock);
>   	/* reset data block */
>   	ctx->data_block = 0;
>   	/* reset reg block */
> @@ -1274,7 +1274,7 @@ int amdgpu_atom_execute_table(struct atom_context *ctx, int index, uint32_t * pa
>   	ctx->divmul[0] = 0;
>   	ctx->divmul[1] = 0;
>   	r = amdgpu_atom_execute_table_locked(ctx, index, params);
> -	mutex_unlock(&ctx->mutex);
> +	spin_unlock(&ctx->lock);
>   	return r;
>   }
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/atom.h b/drivers/gpu/drm/amd/amdgpu/atom.h
> index a391709..cdfb0d0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/atom.h
> +++ b/drivers/gpu/drm/amd/amdgpu/atom.h
> @@ -26,6 +26,7 @@
>   #define ATOM_H
>   
>   #include <linux/types.h>
> +#include <linux/spinlock_types.h>
>   #include <drm/drmP.h>
>   
>   #define ATOM_BIOS_MAGIC		0xAA55
> @@ -125,7 +126,7 @@ struct card_info {
>   
>   struct atom_context {
>   	struct card_info *card;
> -	struct mutex mutex;
> +	spinlock_t lock;
>   	void *bios;
>   	uint32_t cmd_table, data_table;
>   	uint16_t *iio;

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