linux-kernel - Re: [PATCH v2 2/3] dma: imx-sdma: add clock ratio 1:1 check

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Date:   Sun, 20 Jan 2019 07:38:12 -0700
From:   Angus Ainslie <angus@...ea.ca>
To:     Daniel Baluta <daniel.baluta@...il.com>
Cc:     Vinod Koul <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] dma: imx-sdma: add clock ratio 1:1 check

Hi Daniel,

On 2019-01-20 02:58, Daniel Baluta wrote:
> On Sun, Jan 20, 2019 at 4:32 AM Angus Ainslie (Purism) <angus@...ea.ca> 
> wrote:
>> 
>> On i.mx8 mscale B0 chip, AHB/SDMA clock ratio 2:1 can't be supportted,
>> since SDMA clock ratio has to be increased to 250Mhz, AHB can't reach
>> to 500Mhz, so use 1:1 instead.
>> 
>> based on NXP commit MLK-16841-1
> 
> Hi Angus,
> 
> Thanks for doing this!
> 
> I'm not sure specifying the MLK here helps. I think it would be better
> to somehow add the original Signed-off-by and mention that the commit
> was pulled from NXP linux-imx tree.

If it was exactly the same patch I would have but as I added the lines 
in
sdma_run_channel0 I didn't think it would be right to put signed off by
"Robin Gong <yibin.gong@....com>" as the code isn't what he signed off 
on.

>> 
>> Signed-off-by: Angus Ainslie (Purism) <angus@...ea.ca>
>> ---
>>  .../devicetree/bindings/dma/fsl-imx-sdma.txt  |  1 +
>>  drivers/dma/imx-sdma.c                        | 20 
>> +++++++++++++++----
>>  2 files changed, 17 insertions(+), 4 deletions(-)
>> 
>> diff --git a/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt 
>> b/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
>> index 3c9a57a8443b..17544c1820b7 100644
>> --- a/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
>> +++ b/Documentation/devicetree/bindings/dma/fsl-imx-sdma.txt
>> @@ -67,6 +67,7 @@ Optional properties:
>>      reg is the GPR register offset.
>>      shift is the bit position inside the GPR register.
>>      val is the value of the bit (0 or 1).
>> +- fsl,ratio-1-1: AHB/SDMA core clock ration 1:1, 2:1 without this.
>> 
>>  Examples:
>> 
>> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
>> index 0b3a67ff8e82..65dada21d3c1 100644
>> --- a/drivers/dma/imx-sdma.c
>> +++ b/drivers/dma/imx-sdma.c
>> @@ -440,6 +440,8 @@ struct sdma_engine {
>>         unsigned int                    irq;
>>         dma_addr_t                      bd0_phys;
>>         struct sdma_buffer_descriptor   *bd0;
>> +       /* clock ratio for AHB:SDMA core. 1:1 is 1, 2:1 is 0*/
>> +       bool                            clk_ratio;
>>  };
>> 
>>  static int sdma_config_write(struct dma_chan *chan,
>> @@ -662,8 +664,14 @@ static int sdma_run_channel0(struct sdma_engine 
>> *sdma)
>>                 dev_err(sdma->dev, "Timeout waiting for CH0 ready\n");
>> 
>>         /* Set bits of CONFIG register with dynamic context switching 
>> */
>> -       if (readl(sdma->regs + SDMA_H_CONFIG) == 0)
>> -               writel_relaxed(SDMA_H_CONFIG_CSM, sdma->regs + 
>> SDMA_H_CONFIG);
>> +       if (readl(sdma->regs + SDMA_H_CONFIG) == 0) {
>> +               if (sdma->clk_ratio)
>> +                       reg = SDMA_H_CONFIG_CSM | SDMA_H_CONFIG_ACR;
>> +               else
>> +                       reg = SDMA_H_CONFIG_CSM;
>> +
>> +               writel_relaxed(reg, sdma->regs + SDMA_H_CONFIG);
>> +       }
>> 

This is the code that I added out of an over abundance of prudence.

Angus

>>         return ret;
>>  }
>> @@ -1880,8 +1888,10 @@ static int sdma_init(struct sdma_engine *sdma)
>>         writel_relaxed(0x4050, sdma->regs + SDMA_CHN0ADDR);
>> 
>>         /* Set bits of CONFIG register but with static context 
>> switching */
>> -       /* FIXME: Check whether to set ACR bit depending on clock 
>> ratios */
>> -       writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
>> +       if (sdma->clk_ratio)
>> +               writel_relaxed(SDMA_H_CONFIG_ACR, sdma->regs + 
>> SDMA_H_CONFIG);
>> +       else
>> +               writel_relaxed(0, sdma->regs + SDMA_H_CONFIG);
>> 
>>         writel_relaxed(ccb_phys, sdma->regs + SDMA_H_C0PTR);
>> 
>> @@ -1975,6 +1985,8 @@ static int sdma_probe(struct platform_device 
>> *pdev)
>>         if (!sdma)
>>                 return -ENOMEM;
>> 
>> +       sdma->clk_ratio = of_property_read_bool(np, "fsl,ratio-1-1");
>> +
>>         spin_lock_init(&sdma->channel_0_lock);
>> 
>>         sdma->dev = &pdev->dev;
>> --
>> 2.17.1
>>