linux-kernel - Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using dma

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Message-ID: <ed87cf13-a69a-6115-f0a8-5f51c4957d1d@axentia.se>
Date:   Thu, 29 Mar 2018 15:37:43 +0200
From:   Peter Rosin <peda@...ntia.se>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     linux-kernel@...r.kernel.org, Josh Wu <rainyfeeling@...look.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...ev4u.fr>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-mtd@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] mtd: nand: raw: atmel: add module param to avoid using
 dma

On 2018-03-29 15:33, Boris Brezillon wrote:
> On Thu, 29 Mar 2018 15:10:54 +0200
> Peter Rosin <peda@...ntia.se> wrote:
> 
>> On a sama5d31 with a Full-HD dual LVDS panel (132MHz pixel clock) NAND
>> flash accesses have a tendency to cause display disturbances. Add a
>> module param to disable DMA from the NAND controller, since that fixes
>> the display problem for me.
>>
>> Signed-off-by: Peter Rosin <peda@...ntia.se>
>> ---
>>  drivers/mtd/nand/raw/atmel/nand-controller.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mtd/nand/raw/atmel/nand-controller.c b/drivers/mtd/nand/raw/atmel/nand-controller.c
>> index b2f00b398490..2ff7a77c7b8e 100644
>> --- a/drivers/mtd/nand/raw/atmel/nand-controller.c
>> +++ b/drivers/mtd/nand/raw/atmel/nand-controller.c
>> @@ -129,6 +129,11 @@
>>  #define DEFAULT_TIMEOUT_MS			1000
>>  #define MIN_DMA_LEN				128
>>  
>> +static bool atmel_nand_avoid_dma __read_mostly;
>> +
>> +MODULE_PARM_DESC(avoiddma, "Avoid using DMA");
>> +module_param_named(avoiddma, atmel_nand_avoid_dma, bool, 0400);
> 
> I'm not a big fan of those driver specific cmdline parameters. Can't we
> instead give an higher priority to HLCDC master using the bus matrix?

I don't know if it will be enough, but we sure can try. However, I have
no idea how to do that. I will happily test stuff though...

Cheers,
Peter