From: Christoph Hellwig <hch@infradead.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Guo Ren <guoren@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-arch <linux-arch@vger.kernel.org>,
linux-csky@vger.kernel.org, feng_shizhu@dahuatech.com,
zhang_jian5@dahuatech.com, zheng_xingjian@dahuatech.com,
zhu_peng@dahuatech.com, Guo Ren <ren_guo@c-sky.com>
Subject: Re: [PATCH 4/4] csky: Add dma_inv_range for DMA_FROM_DEVICE
Date: Mon, 5 Aug 2019 23:51:15 -0700 [thread overview]
Message-ID: <20190806065115.GB2508@infradead.org> (raw)
In-Reply-To: <CAK8P3a0v3oVS5cCkORxA7na+VE7ofTQRxiv5o5xNf5v=esnN9A@mail.gmail.com>
On Tue, Jul 30, 2019 at 03:43:20PM +0200, Arnd Bergmann wrote:
> When syncing 'for_cpu', you should not need to write back, because
> there won't be any dirty cache lines.
>
> If you have a CPU core that does not do speculative loads, you also don't
> need to invalidate here, because you have already done that in the
> _for_device() case, the only reason to invalidate the CPU cache
> again is if a speculative load created a stale cache line that now
> shadows the data received from the device.
Yes. And that is one reason why I want to lift a set of common helpers
for both the speculating and non-speculating case to the common code
that just calls arch specific writeback/invalidate/writeback+invalidate
helpers. It hasn't been a priotity so far, but maybe it becomes one
now. Especially if I could draft someone else to help with it :)
next prev parent reply other threads:[~2019-08-06 6:51 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-30 12:15 [PATCH 1/4] csky: Fixup dma_rmb/wmb synchronization problem guoren
2019-07-30 12:15 ` [PATCH 2/4] csky: Fixup dma_alloc_coherent with PAGE_SO attribute guoren
2019-07-30 12:15 ` [PATCH 3/4] csky/dma: Fixup cache_op failed when cross memory ZONEs guoren
2019-08-06 6:49 ` Christoph Hellwig
2019-08-06 7:11 ` Guo Ren
2019-08-06 7:18 ` Christoph Hellwig
2019-07-30 12:15 ` [PATCH 4/4] csky: Add dma_inv_range for DMA_FROM_DEVICE guoren
2019-07-30 13:43 ` Arnd Bergmann
2019-07-30 15:11 ` Guo Ren
2019-07-30 15:22 ` Arnd Bergmann
2019-07-30 15:48 ` Guo Ren
2019-08-06 6:51 ` Christoph Hellwig [this message]
2019-07-30 13:29 ` [PATCH 1/4] csky: Fixup dma_rmb/wmb synchronization problem Arnd Bergmann
2019-07-30 15:15 ` Guo Ren
2019-07-30 15:28 ` Guo Ren
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