Re: [PATCH v2] net: ethernet: ti: davinci_cpdma: fix warning "device driver frees DMA memory with different size"

[Ivan Khoronzhuk]

On Sat, Dec 07, 2019 at 01:44:20PM +0200, Ivan Khoronzhuk wrote:
> On Thu, Dec 05, 2019 at 12:48:46PM +0200, Grygorii Strashko wrote:
> > On 04/12/2019 22:37, David Miller wrote:
> > > From: Grygorii Strashko <grygorii.strashko@xxxxxx>
> > > Date: Wed, 4 Dec 2019 18:50:29 +0200
> > >
> > > > @@ -1018,7 +1018,7 @@ static int cpdma_chan_submit_si(struct submit_info *si)
> > > > 	struct cpdma_chan		*chan = si->chan;
> > > > 	struct cpdma_ctlr		*ctlr = chan->ctlr;
> > > > 	int				len = si->len;
> > > > -	int				swlen = len;
> > > > +	int				swlen;
> > > > 	struct cpdma_desc __iomem	*desc;
> > > > 	dma_addr_t			buffer;
> > > > 	u32				mode;
> > > > @@ -1040,6 +1040,7 @@ static int cpdma_chan_submit_si(struct submit_info *si)
> > > > 		chan->stats.runt_transmit_buff++;
> > > > 	}
> > > > +	swlen = len;
> > > > 	mode = CPDMA_DESC_OWNER | CPDMA_DESC_SOP | CPDMA_DESC_EOP;
> > > > 	cpdma_desc_to_port(chan, mode, si->directed);
> > > > --
> > > > 2.17.1
> > >
> > > Now there is no reason to keep a separate swlen variable.
> > >
> > > The integral value is always consumed as the length before the descriptor bits
> > > are added to it.
> > >
> > > Therefore you can just use 'len' everywhere in this function now.
> >
> > Sry, but seems i can't, at least i can't just drop swlen.
> >
> > Below in this function:
> > 	writel_relaxed(0, &desc->hw_next);
> > 	writel_relaxed(buffer, &desc->hw_buffer);
> > 	writel_relaxed(len, &desc->hw_len);
> > 	writel_relaxed(mode | len, &desc->hw_mode);
> > ^^ here the "len" should be use
> >
> > 	writel_relaxed((uintptr_t)si->token, &desc->sw_token);
> > 	writel_relaxed(buffer, &desc->sw_buffer);
> > 	writel_relaxed(swlen, &desc->sw_len);
> > ^^ and here "len"|CPDMA_DMA_EXT_MAP if (si->data_dma) [1]
> >
> > 	desc_read(desc, sw_len);
> >
> > so additional if statement has to be added at [1] if "swlen" is dropped
> >
> > --
> > Best regards,
> > grygorii
>
> Seems like yes,
>
> And the "swlen" can be avoided like this:
>
> --- a/drivers/net/ethernet/ti/davinci_cpdma.c
> +++ b/drivers/net/ethernet/ti/davinci_cpdma.c
> @@ -1018,7 +1018,6 @@ static int cpdma_chan_submit_si(struct submit_info *si)
>       struct cpdma_chan               *chan = si->chan;
>       struct cpdma_ctlr               *ctlr = chan->ctlr;
>       int                             len = si->len;
> -       int                             swlen = len;
>       struct cpdma_desc __iomem       *desc;
>       dma_addr_t                      buffer;
>       u32                             mode;
> @@ -1046,7 +1045,7 @@ static int cpdma_chan_submit_si(struct submit_info *si)
>       if (si->data_dma) {
>               buffer = si->data_dma;
>               dma_sync_single_for_device(ctlr->dev, buffer, len, chan->dir);
> -               swlen |= CPDMA_DMA_EXT_MAP;
> +               writel_relaxed(len | CPDMA_DMA_EXT_MAP, &desc->sw_len);
>       } else {
>               buffer = dma_map_single(ctlr->dev, si->data_virt, len, chan->dir);
>               ret = dma_mapping_error(ctlr->dev, buffer);
> @@ -1054,6 +1053,7 @@ static int cpdma_chan_submit_si(struct submit_info *si)
>                       cpdma_desc_free(ctlr->pool, desc, 1);
>                       return -EINVAL;
>               }
> +               writel_relaxed(len, &desc->sw_len);
>       }
>
>       /* Relaxed IO accessors can be used here as there is read barrier
> @@ -1065,7 +1065,6 @@ static int cpdma_chan_submit_si(struct submit_info *si)
>       writel_relaxed(mode | len, &desc->hw_mode);
>       writel_relaxed((uintptr_t)si->token, &desc->sw_token);
>       writel_relaxed(buffer, &desc->sw_buffer);
> -       writel_relaxed(swlen, &desc->sw_len);
>       desc_read(desc, sw_len);
>
>       __cpdma_chan_submit(chan, desc);
>
> But not sure what is better.

Or like this:

--- a/drivers/net/ethernet/ti/davinci_cpdma.c
+++ b/drivers/net/ethernet/ti/davinci_cpdma.c
@@ -1018,7 +1018,6 @@ static int cpdma_chan_submit_si(struct submit_info *si)
       struct cpdma_chan               *chan = si->chan;
       struct cpdma_ctlr               *ctlr = chan->ctlr;
       int                             len = si->len;
-       int                             swlen = len;
       struct cpdma_desc __iomem       *desc;
       dma_addr_t                      buffer;
       u32                             mode;
@@ -1046,7 +1045,6 @@ static int cpdma_chan_submit_si(struct submit_info *si)
       if (si->data_dma) {
               buffer = si->data_dma;
               dma_sync_single_for_device(ctlr->dev, buffer, len, chan->dir);
-               swlen |= CPDMA_DMA_EXT_MAP;
       } else {
               buffer = dma_map_single(ctlr->dev, si->data_virt, len, chan->dir);
               ret = dma_mapping_error(ctlr->dev, buffer);
@@ -1065,7 +1063,7 @@ static int cpdma_chan_submit_si(struct submit_info *si)
       writel_relaxed(mode | len, &desc->hw_mode);
       writel_relaxed((uintptr_t)si->token, &desc->sw_token);
       writel_relaxed(buffer, &desc->sw_buffer);
-       writel_relaxed(swlen, &desc->sw_len);
+       writel_relaxed(si->data_dma ? len | CPDMA_DMA_EXT_MAP : len, &desc->sw_len);
       desc_read(desc, sw_len);

       __cpdma_chan_submit(chan, desc);

But it's branched twice then.

--
Regards,
Ivan Khoronzhuk