linux-kernel - Re: [PATCH v4 07/15] dmaengine: ti: k3 PSI-L remote endpoint configuration

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Date:   Tue, 5 Nov 2019 12:27:18 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Grygorii Strashko <grygorii.strashko@...com>, <vkoul@...nel.org>,
        <robh+dt@...nel.org>, <nm@...com>, <ssantosh@...nel.org>
CC:     <dan.j.williams@...el.com>, <dmaengine@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <lokeshvutla@...com>, <t-kristo@...com>, <tony@...mide.com>,
        <j-keerthy@...com>
Subject: Re: [PATCH v4 07/15] dmaengine: ti: k3 PSI-L remote endpoint
 configuration



On 05/11/2019 12.00, Grygorii Strashko wrote:
> Hi Peter,
> 
> On 01/11/2019 10:41, Peter Ujfalusi wrote:
>> In K3 architecture the DMA operates within threads. One end of the thread
>> is UDMAP, the other is on the peripheral side.
>>
>> The UDMAP channel configuration depends on the needs of the remote
>> endpoint and it can be differ from peripheral to peripheral.
>>
>> This patch adds database for am654 and j721e and small API to fetch the
>> PSI-L endpoint configuration from the database which should only used by
>> the DMA driver(s).
>>
>> Another API is added for native peripherals to give possibility to
>> pass new
>> configuration for the threads they are using, which is needed to be
>> able to
>> handle changes caused by different firmware loaded for the peripheral for
>> example.
> 
> I have no objection to this approach, but ...
> 
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
>> ---
>>   drivers/dma/ti/Kconfig         |   3 +
>>   drivers/dma/ti/Makefile        |   1 +
>>   drivers/dma/ti/k3-psil-am654.c | 172 ++++++++++++++++++++++++++
>>   drivers/dma/ti/k3-psil-j721e.c | 219 +++++++++++++++++++++++++++++++++
>>   drivers/dma/ti/k3-psil-priv.h  |  39 ++++++
>>   drivers/dma/ti/k3-psil.c       |  97 +++++++++++++++
>>   include/linux/dma/k3-psil.h    |  47 +++++++
>>   7 files changed, 578 insertions(+)
>>   create mode 100644 drivers/dma/ti/k3-psil-am654.c
>>   create mode 100644 drivers/dma/ti/k3-psil-j721e.c
>>   create mode 100644 drivers/dma/ti/k3-psil-priv.h
>>   create mode 100644 drivers/dma/ti/k3-psil.c
>>   create mode 100644 include/linux/dma/k3-psil.h
>>
> 
> [...]
> 
>> diff --git a/include/linux/dma/k3-psil.h b/include/linux/dma/k3-psil.h
>> new file mode 100644
>> index 000000000000..16e9c8c6f839
>> --- /dev/null
>> +++ b/include/linux/dma/k3-psil.h
>> @@ -0,0 +1,47 @@
>> +/* SPDX-License-Identifier: GPL-2.0 */
>> +/*
>> + *  Copyright (C) 2019 Texas Instruments Incorporated -
>> http://www.ti.com
>> + */
>> +
>> +#ifndef K3_PSIL_H_
>> +#define K3_PSIL_H_
>> +
>> +#include <linux/types.h>
>> +
>> +#define K3_PSIL_DST_THREAD_ID_OFFSET 0x8000
>> +
>> +struct device;
>> +
>> +/* Channel Throughput Levels */
>> +enum udma_tp_level {
>> +    UDMA_TP_NORMAL = 0,
>> +    UDMA_TP_HIGH = 1,
>> +    UDMA_TP_ULTRAHIGH = 2,
>> +    UDMA_TP_LAST,
>> +};
>> +
>> +enum psil_endpoint_type {
>> +    PSIL_EP_NATIVE = 0,
>> +    PSIL_EP_PDMA_XY,
>> +    PSIL_EP_PDMA_MCAN,
>> +    PSIL_EP_PDMA_AASRC,
>> +};
>> +
>> +struct psil_endpoint_config {
>> +    enum psil_endpoint_type ep_type;
>> +
>> +    unsigned pkt_mode:1;
>> +    unsigned notdpkt:1;
>> +    unsigned needs_epib:1;
>> +    u32 psd_size;
>> +    enum udma_tp_level channel_tpl;
>> +
>> +    /* PDMA properties, valid for PSIL_EP_PDMA_* */
>> +    unsigned pdma_acc32:1;
>> +    unsigned pdma_burst:1;
>> +};
>> +
>> +int psil_set_new_ep_config(struct device *dev, const char *name,
>> +               struct psil_endpoint_config *ep_config);
>> +
>> +#endif /* K3_PSIL_H_ */
>>
> 
> I see no user now of this public interface, so I think it better to drop
> it until
> there will be real user of it.

The same argument is valid for the glue layer ;)

This is only going to be used by native PSI-L devices and the
psil_endpoint_config is going to be extended to facilitate their needs
to give information to the DMA driver on how to set things up.

I would rather avoid churn later on than adding the support from the start.

The point is that the PSI-L endpoint configuration is part of the PSI-L
peripheral and based on factors these configurations might differ from
the default one. For example if we want to merge the two physical rx
channel for sa2ul (so they use the same rflow) or other things we (I)
can not foresee yet.
Or if different firmware is loaded for them and it affects their PSI-L
configuration.

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
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