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 [thread overview]
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));
> + }
next prev parent reply other threads:[~2020-07-23 13:17 UTC|newest]
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
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