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

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Date:   Mon, 2 Jan 2017 19:14:32 +0100
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        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


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.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>   drivers/staging/fbtft/fbtft-core.c | 1 -
>   1 file changed, 1 deletion(-)
>
> diff --git a/drivers/staging/fbtft/fbtft-core.c b/drivers/staging/fbtft/fbtft-core.c
> index e8bf0d1ec11f..226be8c09768 100644
> --- 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.

Noralf.

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