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From: Peter Ujfalusi <peter.ujfalusi@ti.com>
To: Jon Hunter <jonathanh@nvidia.com>,
	Sameer Pujar <spujar@nvidia.com>, Vinod Koul <vkoul@kernel.org>
Cc: <dan.j.williams@intel.com>, <tiwai@suse.com>,
	<dmaengine@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<sharadg@nvidia.com>, <rlokhande@nvidia.com>,
	<dramesh@nvidia.com>, <mkumard@nvidia.com>,
	linux-tegra <linux-tegra@vger.kernel.org>
Subject: Re: [PATCH] [RFC] dmaengine: add fifo_size member
Date: Fri, 7 Jun 2019 08:50:08 +0300
Message-ID: <d0db90e3-3d05-dfba-8768-28511d9ee3ac@ti.com> (raw)
In-Reply-To: <4593f37c-5e89-8559-4e80-99dbfe4235de@nvidia.com>

Jon,

On 06/06/2019 15.37, Jon Hunter wrote:
>> Looking at the drivers/dma/tegra210-adma.c for the
>> TEGRA*_FIFO_CTRL_DEFAULT definition it is still not clear where the
>> remote FIFO size would fit.
>> There are fields for overflow and starvation(?) thresholds and TX/RX
>> size (assuming word length, 3 == 32bits?).
> 
> The TX/RX size are the FIFO size. So 3 equates to a FIFO size of 3 * 64
> bytes.
> 
>> Both threshold is set to one, so I assume currently ADMA is
>> pushing/pulling data word by word.
> 
> That's different. That indicates thresholds when transfers start.
> 
>> Not sure what the burst size is used for, my guess would be that it is
>> used on the memory (DDR) side for optimized, more efficient accesses?
> 
> That is the actual burst size.
> 
>> My guess is that the threshold values are the counter limits, if the DMA
>> request counter reaches it then ADMA would do a threshold limit worth of
>> push/pull to ADMAIF.
>> Or there is another register where the remote FIFO size can be written
>> and ADMA is counting back from there until it reaches the threshold (and
>> pushes/pulling again threshold amount of data) so it keeps the FIFO
>> filled with at least threshold amount of data?
>>
>> I think in both cases the threshold would be the maxburst.
>>
>> I suppose you have the patch for adma on how to use the fifo_size
>> parameter? That would help understand what you are trying to achieve better.
> 
> Its quite simple, we would just use the FIFO size to set the fields
> TEGRAXXX_ADMA_CH_FIFO_CTRL_TXSIZE/RXSIZE in the
> TEGRAXXX_ADMA_CH_FIFO_CTRL register. That's all.

Hrm, it is still not clear how all of these fits together.

What happens if you configure ADMA side:
BURST = 10
TX/RXSIZE = 100 (100 * 64 bytes?) /* FIFO_SIZE? */
*THRES = 5

And if you change the *THRES to 10?
And if you change the TX/RXSIZE to 50 (50 * 64 bytes?)
And if you change the BURST to 5?

In other words what is the relation between all of these?

There must be a rule and constraints around these and if we do really
need a new parameter for ADMA's FIFO_SIZE I'd like it to be defined in a
generic way so others could benefit without 'misusing' a fifo_size
parameter for similar, but not quite fifo_size information.

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

  parent reply index

Thread overview: 60+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-30 11:30 Sameer Pujar
2019-04-30 11:30 ` [PATCH] " Sameer Pujar
2019-05-02  6:04 ` Vinod Koul
2019-05-02  6:04   ` [PATCH] " Vinod Koul
2019-05-02 10:53   ` Sameer Pujar
2019-05-02 12:25     ` Vinod Koul
2019-05-02 13:29       ` Sameer Pujar
2019-05-03 19:10         ` Peter Ujfalusi
2019-05-04 10:23         ` Vinod Koul
2019-05-06 13:04           ` Sameer Pujar
2019-05-06 15:50             ` Vinod Koul
2019-06-06  3:49               ` Sameer Pujar
2019-06-06  6:00                 ` Peter Ujfalusi
2019-06-06  6:41                   ` Sameer Pujar
2019-06-06  7:14                     ` Jon Hunter
2019-06-06 10:22                       ` Peter Ujfalusi
2019-06-06 10:49                         ` Jon Hunter
2019-06-06 11:54                           ` Peter Ujfalusi
2019-06-06 12:37                             ` Jon Hunter
2019-06-06 13:45                               ` Dmitry Osipenko
2019-06-06 13:55                                 ` Dmitry Osipenko
2019-06-06 14:26                                   ` Jon Hunter
2019-06-06 14:36                                     ` Jon Hunter
2019-06-06 14:36                                     ` Dmitry Osipenko
2019-06-06 14:47                                       ` Jon Hunter
2019-06-06 14:25                                 ` Jon Hunter
2019-06-06 15:18                                   ` Dmitry Osipenko
2019-06-06 16:32                                     ` Jon Hunter
2019-06-06 16:44                                       ` Dmitry Osipenko
2019-06-06 16:53                                         ` Jon Hunter
2019-06-06 17:25                                           ` Dmitry Osipenko
2019-06-06 17:56                                             ` Dmitry Osipenko
2019-06-07  9:24                                             ` Jon Hunter
2019-06-07  5:50                               ` Peter Ujfalusi [this message]
2019-06-07  9:18                                 ` Jon Hunter
2019-06-07 10:27                                   ` Jon Hunter
2019-06-07 12:17                                     ` Peter Ujfalusi
2019-06-07 12:58                                       ` Jon Hunter
2019-06-07 13:35                                         ` Peter Ujfalusi
2019-06-07 20:53                                           ` Dmitry Osipenko
2019-06-10  8:01                                             ` Jon Hunter
2019-06-10  7:59                                           ` Jon Hunter
2019-06-13  4:43                 ` Vinod Koul
2019-06-17  7:07                   ` Sameer Pujar
2019-06-18  4:33                     ` Vinod Koul
2019-06-20 10:29                       ` Sameer Pujar
2019-06-24  6:26                         ` Vinod Koul
2019-06-25  2:57                           ` Sameer Pujar
2019-07-05  6:15                             ` Sameer Pujar
2019-07-15 15:42                               ` Sameer Pujar
2019-07-19  5:04                               ` Vinod Koul
2019-07-23  5:54                                 ` Sameer Pujar
2019-07-29  6:10                                   ` Vinod Koul
2019-07-31  9:48                                     ` Jon Hunter
2019-07-31 15:16                                       ` Vinod Koul
2019-08-02  8:51                                         ` Jon Hunter
2019-08-08 12:38                                           ` Vinod Koul
2019-08-19 15:56                                             ` Jon Hunter
2019-08-20 11:05                                               ` Vinod Koul
2019-09-16  9:02                                                 ` Sameer Pujar

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