Linux-i2c Archive on lore.kernel.org
 help / color / Atom feed
From: Dmitry Osipenko <digetx@gmail.com>
To: Krishna Yarlagadda <kyarlagadda@nvidia.com>,
	linux-i2c@vger.kernel.org, thierry.reding@gmail.com
Cc: jonathanh@nvidia.com, linux-tegra@vger.kernel.org,
	linux-kernel@vger.kernel.org, ldewangan@nvidia.com,
	smohammed@nvidia.com, rgumasta@nvidia.com
Subject: Re: [PATCH 3/7] i2c: tegra: add flag for register write buffering
Date: Thu, 23 Jul 2020 16:17:40 +0300
Message-ID: <fd8d2650-6450-be61-cd78-f57871984e4f@gmail.com> (raw)
In-Reply-To: <1595506733-10307-3-git-send-email-kyarlagadda@nvidia.com>

23.07.2020 15:18, Krishna Yarlagadda пишет:
> In chips earlier to Tegra186, register write gets buffered. So to make
> sure register writes are completed, there is need to readback the
> register. Adding flag to disable this readback for Tegra186 and later
> chips.
> 
> Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index a841d6c..bdbbca0 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -220,6 +220,7 @@ struct tegra_i2c_hw_feature {
>  	bool has_mst_fifo;
>  	const struct i2c_adapter_quirks *quirks;
>  	bool supports_bus_clear;
> +	bool has_reg_write_buffering;
>  	bool has_apb_dma;
>  	u8 tlow_std_mode;
>  	u8 thigh_std_mode;
> @@ -325,8 +326,11 @@ static void i2c_writel(struct tegra_i2c_dev *i2c_dev, u32 val,
>  	writel_relaxed(val, i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
>  
>  	/* Read back register to make sure that register writes completed */
> -	if (reg != I2C_TX_FIFO)
> -		readl_relaxed(i2c_dev->base + tegra_i2c_reg_addr(i2c_dev, reg));
> +	if (i2c_dev->hw->has_reg_write_buffering) {
> +		if (reg != I2C_TX_FIFO)

Should be single line.

What problem does this solve? If there is no visible effect, then please
drop this patch.

> +			readl_relaxed(i2c_dev->base +
> +				      tegra_i2c_reg_addr(i2c_dev, reg));
> +	}

  reply index

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23 12:18 [PATCH 1/7] i2c: tegra: remove dead code Krishna Yarlagadda
2020-07-23 12:18 ` [PATCH 2/7] i2c: tegra: Fix setting of controller ID Krishna Yarlagadda
2020-07-23 12:18 ` [PATCH 3/7] i2c: tegra: add flag for register write buffering Krishna Yarlagadda
2020-07-23 13:17   ` Dmitry Osipenko [this message]
2020-07-23 12:18 ` [PATCH 4/7] i2c: tegra: add high speed mode support Krishna Yarlagadda
2020-07-23 13:27   ` Dmitry Osipenko
2020-07-25 11:26   ` Michał Mirosław
2020-07-23 12:18 ` [PATCH 5/7] i2c: tegra: enable second level clock gating Krishna Yarlagadda
2020-07-23 14:01   ` Dmitry Osipenko
2020-07-23 12:18 ` [PATCH 6/7] i2c: tegra: DMA support for t186 and t194 Krishna Yarlagadda
2020-07-23 13:16   ` Dmitry Osipenko
2020-07-23 13:38   ` Dmitry Osipenko
2020-07-23 12:18 ` [PATCH 7/7] i2c: tegra: dump I2C registers on timeout Krishna Yarlagadda

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=fd8d2650-6450-be61-cd78-f57871984e4f@gmail.com \
    --to=digetx@gmail.com \
    --cc=jonathanh@nvidia.com \
    --cc=kyarlagadda@nvidia.com \
    --cc=ldewangan@nvidia.com \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-tegra@vger.kernel.org \
    --cc=rgumasta@nvidia.com \
    --cc=smohammed@nvidia.com \
    --cc=thierry.reding@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-i2c Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-i2c/0 linux-i2c/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-i2c linux-i2c/ https://lore.kernel.org/linux-i2c \
		linux-i2c@vger.kernel.org
	public-inbox-index linux-i2c

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-i2c


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git