linux-kernel - Re: [PATCH] i2c: tegra: Fix i2c-tegra DMA config option processing

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Date:   Mon, 14 Aug 2023 18:25:24 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Andi Shyti <andi.shyti@...nel.org>,
        Parker Newman <pnewman@...necttech.com>
Cc:     Laxman Dewangan <ldewangan@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: tegra: Fix i2c-tegra DMA config option processing

05.08.2023 00:49, Andi Shyti пишет:
> Hi Laxman and/or Dmitry,
> 
> On Thu, Aug 03, 2023 at 05:10:02PM +0000, Parker Newman wrote:
>>
>> This patch fixes the Tegra DMA config option processing in the
>> i2c-tegra driver.
>>
>> Tegra processors prior to Tegra186 used APB DMA for I2C requiring
>> CONFIG_TEGRA20_APB_DMA=y while Tegra186 and later use GPC DMA requiring
>> CONFIG_TEGRA186_GPC_DMA=y.
>>
>> The check for if the processor uses APB DMA is inverted and so the wrong
>> DMA config options are checked.
>>
>> This means if CONFIG_TEGRA20_APB_DMA=y but CONFIG_TEGRA186_GPC_DMA=n
>> with a Tegra186 or later processor the driver will incorrectly think DMA is
>> enabled and attempt to request DMA channels that will never be availible,
>> leaving the driver in a perpetual EPROBE_DEFER state.
>>
>> Signed-off-by: Parker Newman <pnewman@...necttech.com>
>> ---
>>  drivers/i2c/busses/i2c-tegra.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
>> index bcbbf23aa530..dc6ed3a8d69e 100644
>> --- a/drivers/i2c/busses/i2c-tegra.c
>> +++ b/drivers/i2c/busses/i2c-tegra.c
>> @@ -442,7 +442,7 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
>>     if (IS_VI(i2c_dev))
>>         return 0;
>>
>> -   if (!i2c_dev->hw->has_apb_dma) {
>> +   if (i2c_dev->hw->has_apb_dma) {
>>         if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA)) {
>>             dev_dbg(i2c_dev->dev, "APB DMA support not enabled\n");
>>             return 0;
> 
> Can I have your opinion here, please?

The patch looks good, thanks Parker for fixing it. I'll be able to test
it only sometime later and let you all know if there will be any
problem. Previously I haven't noticed any Tegra I2C regressions, maybe
we should change that dev_dbg to dev_warn.