linux-kernel - Re: [PATCH] dmaengine: ti: omap-dma: Configure LCH

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Message-ID: <6af8c6e7-bf5c-5555-161b-5d3fb7ecae43@ti.com>
Date:   Tue, 20 Nov 2018 09:28:37 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Aaro Koskinen <aaro.koskinen@....fi>
CC:     <vkoul@...nel.org>, <dan.j.williams@...el.com>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <tony@...mide.com>, <linux-omap@...r.kernel.org>,
        <rmk+kernel@...linux.org.uk>
Subject: Re: [PATCH] dmaengine: ti: omap-dma: Configure LCH_TYPE for OMAP1

Aaro,

On 19/11/2018 20.46, Aaro Koskinen wrote:
> Hi,
> 
> On Mon, Nov 19, 2018 at 12:40:40PM +0200, Peter Ujfalusi wrote:
>> When the channel is configured for slave operation the LCH_TYPE needs to be
>> set to LCh-P. For memcpy channels the LCH_TYPE must be set to LCh-2D.
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> 
> I don't have the documentation, but based on what omap_udc driver (still
> using the legacy OMAP DMA API) does this seems to be correct.

They are hard to fine, true. From the omap1710 TRM:

Logical channel types (LCh types) supported are:
- LCh-2D for nonsynchronized transfers (memory transfers, 1D and 2D)
- LCh-P for synchronized transfers (mostly peripheral transfers)
- LCh-PD similar to LCh-P but runs on a dedicated physical channel
- LCh-G for graphical transfers/operations
- LCh-D for display transfers

Looking at other part it looks like hat LCH-2D channel mode can happily
service a peripheral. LCH-P supports the same features as LCH-2D, but it
lacks support for Single/Double-indexed addressing mode on the
peripheral port side.

So, this patch might not be needed at all. Can you test the omap_udc
with s/OMAP_DMA_LCH_P/OMAP_DMA_LCH_2D

If USB works, then we can just drop this patch.

Note: if we ever need the port_window support in OMAP1 then we need
double indexing on the peripheral side.

> I tested the patch on Nokia 770 with MMC and couldn't see any negative
> impact.
> 
> Tested-by: Aaro Koskinen <aaro.koskinen@....fi>
> 
> A.
> 
>> ---
>>  drivers/dma/ti/omap-dma.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
>> index a4a931ddf6f6..a18cfd497f04 100644
>> --- a/drivers/dma/ti/omap-dma.c
>> +++ b/drivers/dma/ti/omap-dma.c
>> @@ -185,6 +185,10 @@ enum {
>>  
>>  	CLNK_CTRL_ENABLE_LNK	= BIT(15),
>>  
>> +	/* OMAP1 only */
>> +	LCH_CTRL_LCH_2D		= 0,
>> +	LCH_CTRL_LCH_P		= 2,
>> +
>>  	CDP_DST_VALID_INC	= 0 << 0,
>>  	CDP_DST_VALID_RELOAD	= 1 << 0,
>>  	CDP_DST_VALID_REUSE	= 2 << 0,
>> @@ -529,6 +533,7 @@ static void omap_dma_start_sg(struct omap_chan *c, struct omap_desc *d)
>>  
>>  static void omap_dma_start_desc(struct omap_chan *c)
>>  {
>> +	struct omap_dmadev *od = to_omap_dma_dev(c->vc.chan.device);
>>  	struct virt_dma_desc *vd = vchan_next_desc(&c->vc);
>>  	struct omap_desc *d;
>>  	unsigned cxsa, cxei, cxfi;
>> @@ -570,6 +575,12 @@ static void omap_dma_start_desc(struct omap_chan *c)
>>  	omap_dma_chan_write(c, CSDP, d->csdp);
>>  	omap_dma_chan_write(c, CLNK_CTRL, d->clnk_ctrl);
>>  
>> +	if (dma_omap1() && !__dma_omap15xx(od->plat->dma_attr)) {
>> +		if (is_slave_direction(d->dir))
>> +			omap_dma_chan_write(c, LCH_CTRL, LCH_CTRL_LCH_P);
>> +		else
>> +			omap_dma_chan_write(c, LCH_CTRL, LCH_CTRL_LCH_2D);
>> +	}
>>  	omap_dma_start_sg(c, d);
>>  }
>>  
>> -- 
>> Peter
>>
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>

- Péter

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