linux-kernel - Re: [PATCH] dmaengine: edma: Reject slave configs using a buswidth of 8 and larger

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Date:   Fri, 22 Sep 2017 14:13:35 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     Stefan Brüns <stefan.bruens@...h-aachen.de>,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] dmaengine: edma: Reject slave configs using a buswidth
 of 8 and larger

On Fri, Sep 22, 2017 at 09:16:13AM +0300, Peter Ujfalusi wrote:
> Stefan, Vinod,
> 
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 
> On 2017-09-21 21:29, Peter Ujfalusi wrote:
> > 
> > 
> > On 2017-09-21 20:17, Vinod Koul wrote:
> >> On Sun, Sep 17, 2017 at 04:25:10PM +0200, Stefan Brüns wrote:
> >>> The driver would happily accept buswidth of 16/32/64 bytes and program
> >>> garbage to its registers.
> >>
> >> Peter?
> > 
> > Well, eDMA as such has no limitation on the buswidth, the addr_width
> > become ACNT, counter for the inner loop - which we use to represent the
> > word length. In theory we could support 32K-1 long word with eDMA, which
> > we actually do in case of memcpy.
> > 
> > But the driver does state that it supports bus width of 1, 2, 3 and 4 bytes.
> > 
> > These are form the past and I never felt the need to check them.
> > 
> > I think it is fine to reject salve config when asking for longer dev
> > width. I might revisit later if the need comes..
> > 
> > Acked-by: Peter Ujfalusi <peter.ujfalusi@...com>
> 
> If it is not too late, I have second thoughts about this..
> It might be better to remove the src_addr_width/dst_addr_width check
> from edma_slave_config() and add all DMA_SLAVE_BUSWIDTH_* to
> EDMA_DMA_BUSWIDTHS.

fine by me, pls send updated..

-- 
~Vinod