linux-kernel - Re: [PATCH v2 2/6] staging: fbtft: do not override DMA coherent mask

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Date:   Tue, 03 Jan 2017 12:51:04 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Noralf Trønnes <noralf@...nnes.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/6] staging: fbtft: do not override DMA coherent mask

On Mon, 2017-01-02 at 19:14 +0100, Noralf Trønnes wrote:
> Den 02.01.2017 12:35, skrev Andy Shevchenko:
> > Usually it's not consumer's business to override resources passed
> > from
> > provider, in particularly DMA coherent mask.

> > --- a/drivers/staging/fbtft/fbtft-core.c
> > +++ b/drivers/staging/fbtft/fbtft-core.c
> > @@ -841,7 +841,6 @@ struct fb_info *fbtft_framebuffer_alloc(struct
> > fbtft_display *display,
> >   	if (txbuflen > 0) {
> >   #ifdef CONFIG_HAS_DMA
> >   		if (dma) {
> > -			dev->coherent_dma_mask = ~0;
> 
> Can we make this conditional like in of_dma_configure():
> 
>           if (!dev->coherent_dma_mask)
>                  dev->coherent_dma_mask = DMA_BIT_MASK(32);
> 
> If not, I guess the mask has to be set before adding the spi device in
> fbtft_device.c to keep it from breaking.

Good point. I will check this.

>  			txbuf = dmam_alloc_coherent(dev, txbuflen,
> >   						    &par-
> > >txbuf.dma, GFP_DMA);
> >   		} else

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy