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Message-ID: <cf5wxalhd2536cxnj7zn2jngly5dmvoknjnb2gbq6mzqff4tgp@4syhblgi35yu>
Date: Tue, 19 Aug 2025 20:09:48 -0100
From: Andi Shyti <andi.shyti@...nel.org>
To: Leilk Liu <leilk.liu@...iatek.com>
Cc: Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Qii Wang <qii.wang@...iatek.com>, Wolfram Sang <wsa@...nel.org>,
Liguo Zhang <liguo.zhang@...iatek.com>, linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH] i2c: mediatek: fix potential incorrect use of
I2C_MASTER_WRRD
Hi Leilk,
On Sat, Aug 16, 2025 at 03:53:54PM +0800, Leilk Liu wrote:
> From: "Leilk.Liu" <leilk.liu@...iatek.com>
>
> The old IC does not support the I2C_MASTER_WRRD (write-then-read)
> function, but the current code’s handling of i2c->auto_restart may
> potentially lead to entering the I2C_MASTER_WRRD software flow,
> resulting in unexpected bugs.
do you mean unexpected behaviour?
> Instead of repurposing the auto_restart flag, add a separate flag
> to signal I2C_MASTER_WRRD operations.
>
> Also fix handling of msgs. If the operation (i2c->op) is
> I2C_MASTER_WRRD, then the msgs pointer is incremented by 2.
> For all other operations, msgs is simply incremented by 1.
>
> Fixes: 173b77e8d8fe ("i2c: mediatek: add i2c first write then read optimization")
>
No need for blank line here. BTW, this doesn't look the commit
that is introducing the issue.
> Signed-off-by: Leilk.Liu <leilk.liu@...iatek.com>
> ---
> drivers/i2c/busses/i2c-mt65xx.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-mt65xx.c b/drivers/i2c/busses/i2c-mt65xx.c
> index ab456c3717db..dee40704825c 100644
> --- a/drivers/i2c/busses/i2c-mt65xx.c
> +++ b/drivers/i2c/busses/i2c-mt65xx.c
> @@ -1243,6 +1243,7 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
> {
> int ret;
> int left_num = num;
> + bool write_then_read_en = false;
> struct mtk_i2c *i2c = i2c_get_adapdata(adap);
>
> ret = clk_bulk_enable(I2C_MT65XX_CLK_MAX, i2c->clocks);
> @@ -1256,6 +1257,7 @@ static int mtk_i2c_transfer(struct i2c_adapter *adap,
> if (!(msgs[0].flags & I2C_M_RD) && (msgs[1].flags & I2C_M_RD) &&
> msgs[0].addr == msgs[1].addr) {
> i2c->auto_restart = 0;
> + write_then_read_en = true;
why don't we set "i2c->op = I2C_MASTER_WRRD" here and avoid an
extra flag?
Thanks,
Andi
> }
> }
>
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