linux-kernel - Re: [PATCH v8 1/5] drm/panthor: introduce job cycle and timestamp accounting

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Message-ID: <20241002103809.26d34ee0@collabora.com>
Date: Wed, 2 Oct 2024 10:38:09 +0200
From: Boris Brezillon <boris.brezillon@...labora.com>
To: Adrián Larumbe <adrian.larumbe@...labora.com>
Cc: Steven Price <steven.price@....com>, Liviu Dudau <liviu.dudau@....com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard
 <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie
 <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Sumit Semwal
 <sumit.semwal@...aro.org>, Christian König
 <christian.koenig@....com>, kernel@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH v8 1/5] drm/panthor: introduce job cycle and timestamp
 accounting

On Tue, 24 Sep 2024 00:06:21 +0100
Adrián Larumbe <adrian.larumbe@...labora.com> wrote:

> +static u32 calc_profiling_ringbuf_num_slots(struct panthor_device *ptdev,
> +				       u32 cs_ringbuf_size)
> +{
> +	u32 min_profiled_job_instrs = U32_MAX;
> +	u32 last_flag = fls(PANTHOR_DEVICE_PROFILING_ALL);
> +
> +	/*
> +	 * We want to calculate the minimum size of a profiled job's CS,
> +	 * because since they need additional instructions for the sampling
> +	 * of performance metrics, they might take up further slots in
> +	 * the queue's ringbuffer. This means we might not need as many job
> +	 * slots for keeping track of their profiling information. What we
> +	 * need is the maximum number of slots we should allocate to this end,
> +	 * which matches the maximum number of profiled jobs we can place
> +	 * simultaneously in the queue's ring buffer.
> +	 * That has to be calculated separately for every single job profiling
> +	 * flag, but not in the case job profiling is disabled, since unprofiled
> +	 * jobs don't need to keep track of this at all.
> +	 */
> +	for (u32 i = 0; i < last_flag; i++) {
> +		if (BIT(i) & PANTHOR_DEVICE_PROFILING_ALL)

I'll get rid of this check when applying, as suggested by Steve. Steve,
with this modification do you want me to add your R-b?

BTW, I've also fixed a bunch of checkpatch errors/warnings, so you
might want to run checkpatch --strict next time.

> +			min_profiled_job_instrs =
> +				min(min_profiled_job_instrs, calc_job_credits(BIT(i)));
> +	}
> +
> +	return DIV_ROUND_UP(cs_ringbuf_size, min_profiled_job_instrs * sizeof(u64));
> +}