Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

From: Niklas Cassel Date: Mon, 12 Mar 2018 09:55:42 +0100 > Jose is simply responding to the commit message description of this patch. > > You explained that there is an implicit memory barrier between physical memory > writes and those to MMIO register space, as long as

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

From: Niklas Cassel Date: Mon, 12 Mar 2018 09:55:42 +0100 > Jose is simply responding to the commit message description of this patch. > > You explained that there is an implicit memory barrier between physical memory > writes and those to MMIO register space, as long as you used writel(). > >

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

On Fri, Mar 09, 2018 at 10:15:20AM -0500, David Miller wrote: > From: Jose Abreu > Date: Fri, 9 Mar 2018 10:26:11 + > > > Sorry but I know at least two architectures which don't do a > > wmb() upon an writel [1] [2]. This can be critical if if we are > > accessing

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

On Fri, Mar 09, 2018 at 10:15:20AM -0500, David Miller wrote: > From: Jose Abreu > Date: Fri, 9 Mar 2018 10:26:11 + > > > Sorry but I know at least two architectures which don't do a > > wmb() upon an writel [1] [2]. This can be critical if if we are > > accessing the device through some

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

From: Jose Abreu Date: Fri, 9 Mar 2018 10:26:11 + > Sorry but I know at least two architectures which don't do a > wmb() upon an writel [1] [2]. This can be critical if if we are > accessing the device through some slow or filled bus which will > delay accesses to

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

From: Jose Abreu Date: Fri, 9 Mar 2018 10:26:11 + > Sorry but I know at least two architectures which don't do a > wmb() upon an writel [1] [2]. This can be critical if if we are > accessing the device through some slow or filled bus which will > delay accesses to the device IO. Notice that

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

On Fri 2018-03-09 10:26:11, Jose Abreu wrote: > Hi Niklas, > > On 08-03-2018 10:30, Niklas Cassel wrote: > > These wmb() memory barriers are performed after the last descriptor write, > > and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), > > i.e. a writel() to MMIO register

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

On Fri 2018-03-09 10:26:11, Jose Abreu wrote: > Hi Niklas, > > On 08-03-2018 10:30, Niklas Cassel wrote: > > These wmb() memory barriers are performed after the last descriptor write, > > and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), > > i.e. a writel() to MMIO register

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

Hi Niklas, On 08-03-2018 10:30, Niklas Cassel wrote: > These wmb() memory barriers are performed after the last descriptor write, > and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), > i.e. a writel() to MMIO register space. > Since writel() itself performs the equivalent of a

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

Hi Niklas, On 08-03-2018 10:30, Niklas Cassel wrote: > These wmb() memory barriers are performed after the last descriptor write, > and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), > i.e. a writel() to MMIO register space. > Since writel() itself performs the equivalent of a

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

From: Niklas Cassel Date: Thu, 8 Mar 2018 11:30:05 +0100 > These wmb() memory barriers are performed after the last descriptor write, > and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), > i.e. a writel() to MMIO register space. > Since writel() itself

Re: [PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

From: Niklas Cassel Date: Thu, 8 Mar 2018 11:30:05 +0100 > These wmb() memory barriers are performed after the last descriptor write, > and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), > i.e. a writel() to MMIO register space. > Since writel() itself performs the equivalent

[PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

These wmb() memory barriers are performed after the last descriptor write, and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), i.e. a writel() to MMIO register space. Since writel() itself performs the equivalent of a wmb() before doing the actual write, these barriers are

[PATCH net-next] net: stmmac: remove superfluous wmb() memory barriers

These wmb() memory barriers are performed after the last descriptor write, and they are followed by enable_dma_transmission()/set_tx_tail_ptr(), i.e. a writel() to MMIO register space. Since writel() itself performs the equivalent of a wmb() before doing the actual write, these barriers are