From: Wolfram Sang <wsa@the-dreams.de>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: Sowjanya Komatineni <skomatineni@nvidia.com>,
thierry.reding@gmail.com, jonathanh@nvidia.com,
mkarthik@nvidia.com, smohammed@nvidia.com, talho@nvidia.com,
peda@axentia.se, linux-tegra@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org
Subject: Re: [PATCH V18 4/6] i2c: tegra: Add DMA support
Date: Mon, 11 Feb 2019 14:28:51 +0100 [thread overview]
Message-ID: <20190211132851.pxrawigdgggoc32k@ninjato> (raw)
In-Reply-To: <ed92df42-459e-26fd-ce4e-f4530bf30783@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2331 bytes --]
Hi Dmitry,
> > I am not sure if you are aware of this document, so I mention it:
> >
> > Documentation/i2c/DMA-considerations
> >
> > I am not pushing you to use the i2c_get_dma_safe_msg_buf() helpers,
> > just wanted to make sure you know about them. I am also fine with an
> > incremental patch on top of this if you want to add usage of those
> > helpers somewhen later.
>
> At least I was not aware of those helpers. It looks to me that the
> approach of having a statically allocated buffer is more optimal than
> having to allocate and map the buffer on each transfer.
Can be argued, yes.
> >> /* Match table for of_platform binding */
> >> static const struct of_device_id tegra_i2c_of_match[] = {
> >> { .compatible = "nvidia,tegra194-i2c", .data = &tegra194_i2c_hw, },
> >> + { .compatible = "nvidia,tegra186-i2c", .data = &tegra186_i2c_hw, },
> >> { .compatible = "nvidia,tegra210-i2c", .data = &tegra210_i2c_hw, },
> >> { .compatible = "nvidia,tegra124-i2c", .data = &tegra124_i2c_hw, },
> >> { .compatible = "nvidia,tegra114-i2c", .data = &tegra114_i2c_hw, },
> >
> > Shouldn't this be a seperate patch?
>
> I asked for this change and no, it shouldn't be a separate patch as it
> adds "has_apb_dma = false" property for T186 that older Tegra's have
> as "true". Without this change T186 uses tegra_i2c_hw_feature of T210,
> see [0]. Hence this change is absolutely correct and appropriate for
> this patch.
Then please update the patch description to contain this information.
> > This should definately be a seperate patch. While I am all for taking
> > it, are you sure it does not regress on older Tegra platforms?
> >
>
> All the patches are tested on older Tegra's (T20/T30 specifically by
> me) and we fixed several bugs that were regressing them over the few
> versions of the patchset. I specifically asked for this change for
> older Tegra's because the APBDMA driver (T20-T210) is getting
> registered from the module-init level and hence I2C driver probe is
> always getting deferred. I'm not sure that it's worth to factor out
> this hunk into a separate patch as it's directly related to the DMA
> support addition, maybe worth to mention why this is needed in the
> commit message.
At least, this, yes.
Thanks,
Wolfram
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next prev parent reply other threads:[~2019-02-11 13:28 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-08 18:59 [PATCH V18 1/6] i2c: tegra: sort all the include headers alphabetically Sowjanya Komatineni
2019-02-08 18:59 ` [PATCH V18 2/6] i2c: tegra: add bus clear Master Support Sowjanya Komatineni
2019-02-11 12:44 ` Wolfram Sang
2019-02-11 20:18 ` Sowjanya Komatineni
2019-02-08 18:59 ` [PATCH V18 3/6] i2c: tegra: fix maximum transfer size Sowjanya Komatineni
2019-02-08 18:59 ` [PATCH V18 4/6] i2c: tegra: Add DMA support Sowjanya Komatineni
2019-02-11 12:55 ` Wolfram Sang
2019-02-11 13:22 ` Dmitry Osipenko
2019-02-11 13:28 ` Wolfram Sang [this message]
2019-02-11 16:26 ` Sowjanya Komatineni
2019-02-08 18:59 ` [PATCH V18 5/6] i2c: tegra: update transfer timeout Sowjanya Komatineni
2019-02-08 18:59 ` [PATCH V18 6/6] i2c: tegra: add i2c interface timing support Sowjanya Komatineni
2019-02-11 13:03 ` Wolfram Sang
2019-02-11 16:23 ` Sowjanya Komatineni
2019-02-11 12:45 ` [PATCH V18 1/6] i2c: tegra: sort all the include headers alphabetically Wolfram Sang
2019-02-11 13:06 ` Wolfram Sang
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