linux-kernel - Re: [PATCH v1] dma: imx-sdma: switch to dynamic context mode after script loaded

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Date:	Thu, 22 Jan 2015 11:32:05 +0800
From:	Robin Gong <b38343@...escale.com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	<vinod.koul@...el.com>, <dan.j.williams@...el.com>,
	<dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1] dma: imx-sdma: switch to dynamic context mode after
 script loaded

On Tue, Jan 20, 2015 at 08:16:14AM +0100, Sascha Hauer wrote:
> On Tue, Jan 13, 2015 at 01:09:17PM +0800, Robin Gong wrote:
> > Below comments got from Page4724 of Reference Manual of i.mx6q:
> > http://cache.freescale.com/files/32bit/doc/ref_manual/IMX6DQRM.pdf
> > 
> > --"Static context mode should be used for the first channel called
> > after reset to ensure that the all context RAM for that channel is
> > initialized during the context SAVE phase when the channel is
> > done or yields. Subsequent calls to the same channel or
> > different channels may use any of the dynamic context modes.
> > This will ensure that all context locations for the bootload
> > channel are initialized, and prevent undefined values in context
> > RAM from being loaded during the context restore if the
> > channel is re-started later"
> > 
> > Unfortunately, the rule was broken by commit(5b28aa319bba96987316425a1131813d87cbab35)
> > .This patch just take them back.
> > 
> > Signed-off-by: Robin Gong <b38343@...escale.com>
> > ---
> >  drivers/dma/imx-sdma.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> > index d0df198..510e463 100644
> > --- a/drivers/dma/imx-sdma.c
> > +++ b/drivers/dma/imx-sdma.c
> > @@ -1323,6 +1323,10 @@ static void sdma_load_firmware(const struct firmware *fw, void *context)
> >  	sdma_load_script(sdma, ram_code,
> >  			header->ram_code_size,
> >  			addr->ram_code_start_addr);
> > +
> > +	/* Set bits of CONFIG register with given context switching mode */
> > +	writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + SDMA_H_CONFIG);
> > +
> 
> You move the CONFIG register initialization to a place which may never
> be called. Look at the top of sdma_load_firmware:
> 
> 	if (!fw) {
> 		dev_info(sdma->dev, "external firmware not found, using ROM firmware\n");
> 		/* In this case we just use the ROM firmware. */
> 		return;
> 	}
> 
> Sascha
>
Yes. I'll move it into sdma_run_channel0.
> -- 
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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