netdev - Re: [PATCH V3 2/6] net: stmmac: stop each tx channel independently

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Date:   Tue, 26 Jan 2021 21:16:48 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Joakim Zhang <qiangqing.zhang@....com>
Cc:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Jose Abreu <joabreu@...opsys.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Network Development <netdev@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH V3 2/6] net: stmmac: stop each tx channel independently

On Tue, Jan 26, 2021 at 8:44 PM Joakim Zhang <qiangqing.zhang@....com> wrote:
>
>
> > -----Original Message-----
> > From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> > Sent: 2021年1月27日 7:10
> > To: Joakim Zhang <qiangqing.zhang@....com>
> > Cc: Giuseppe Cavallaro <peppe.cavallaro@...com>; Alexandre Torgue
> > <alexandre.torgue@...com>; Jose Abreu <joabreu@...opsys.com>; David
> > Miller <davem@...emloft.net>; Jakub Kicinski <kuba@...nel.org>; Network
> > Development <netdev@...r.kernel.org>; dl-linux-imx <linux-imx@....com>;
> > Andrew Lunn <andrew@...n.ch>; Florian Fainelli <f.fainelli@...il.com>
> > Subject: Re: [PATCH V3 2/6] net: stmmac: stop each tx channel independently
> >
> > On Tue, Jan 26, 2021 at 7:03 AM Joakim Zhang <qiangqing.zhang@....com>
> > wrote:
> > >
> > > If clear GMAC_CONFIG_TE bit, it would stop all tx channels, but users
> > > may only want to stop secific tx channel.
> >
> > secific -> specific
>
> Thanks. Will correct it.
>
> > >
> > > Fixes: 48863ce5940f ("stmmac: add DMA support for GMAC 4.xx")
> > > Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> > > ---
> > >  drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c | 4 ----
> > >  1 file changed, 4 deletions(-)
> > >
> > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> > > b/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> > > index 0b4ee2dbb691..71e50751ef2d 100644
> > > --- a/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac4_lib.c
> > > @@ -53,10 +53,6 @@ void dwmac4_dma_stop_tx(void __iomem *ioaddr,
> > u32
> > > chan)
> > >
> > >         value &= ~DMA_CONTROL_ST;
> > >         writel(value, ioaddr + DMA_CHAN_TX_CONTROL(chan));
> > > -
> > > -       value = readl(ioaddr + GMAC_CONFIG);
> > > -       value &= ~GMAC_CONFIG_TE;
> > > -       writel(value, ioaddr + GMAC_CONFIG);
> >
> > Is it safe to partially unwind the actions of dwmac4_dma_start_tx
> >
> > And would the same reasoning apply to dwmac4_(dma_start|stop)_rx?
>
> Sorry, I am not quite understand what you means.
>
> What this patch did is to align to dwmac4_(dma_start|stop)_rx.
>
> dwmac4_dma_start_rx: assert DMA_CONTROL_SR bit for each channel, and assert GMAC_CONFIG_RE bit which targets all channels.
> dwmac4_dma_stop_rx: only need clear DMA_CONTROL_SR bit for each channel.
>
> After this patch applied:
> dwmac4_dma_start_tx: assert DMA_CONTROL_ST bit for each channel, and assert GMAC_CONFIG_TE bit which targets all channels.
> dwmac4_dma_stop_tx: only need clear DMA_CONTROL_ST bit for each channel.

Oh indeed. Sorry, I should have seen that it exactly brings the tx
logic into agreement with rx. Thanks.