Re: [PATCH v4] i2c: qcom-geni: Add support for GPI DMA

[Vinod Koul <vkoul@kernel.org>]

Hello Alexey,

On 03-11-21, 05:13, Alexey Minnekhanov wrote:
> 19.10.2021 09:01, Vinod Koul wrote:
> > This adds capability to use GSI DMA for I2C transfers
> > 
> > Signed-off-by: Vinod Koul <vkoul@kernel.org>
> > ---
> > Changes since v3:
> >   - remove separate tx and rx function for gsi dma and make a common one
> >   - remove global structs and use local variables instead
> > 
> 
> Hi, I've tried this patch on sm8150 board and I'm seeing weird things:
> 
> [    0.428829] gpi c00000.dma-controller: Adding to iommu group 0
> [    0.480453] geni_se_qup cc0000.geniqup: Adding to iommu group 1
> [    0.484019] geni_i2c c80000.i2c: Bus frequency not specified, default to
> 100kHz.
> [    0.487172] geni_i2c c80000.i2c: error 0000000000000000: Failed to get tx
> DMA ch
> [    0.495499] geni_i2c c80000.i2c: error 0000000000000000: Failed to get rx
> DMA ch
> [    0.499842] geni_i2c c80000.i2c: Grabbed GPI dma channels
> [    0.504784] geni_i2c c80000.i2c: Using GPI DMA mode for I2C
> [    0.510812] geni_i2c c80000.i2c: Geni-I2C adaptor successfully added
> 
> It seems weird to me that it "failed to get DMA channels", but then says
> anyway "Grabbed GPI DMA channels" and "Using GPI DMA mode for I2C".
> 
> What I did in dts is basically include sm8150.dtsi and do
> 
> &gpi_dma2 {
> 	status = "okay";
> };
> 
> &i2c17 {
> 	status = "okay";
> 	dmas = <&gpi_dma2 0 0 QCOM_GPI_I2C>,
> 		<&gpi_dma2 1 0 QCOM_GPI_I2C>;
> 	dma-names = "tx", "rx";
> 	/* empty - no clients */
> }
> 
> Another observation, even if I comment out "dmas" and "dma-names" in i2c17
> node, I get
> 
> [    0.487037] geni_i2c c80000.i2c: error (____ptrval____): Failed to get tx
> DMA ch
> [    0.490077] geni_i2c c80000.i2c: error (____ptrval____): Failed to get rx
> DMA ch
> [    0.493077] geni_i2c c80000.i2c: Grabbed GPI dma channels
> [    0.496061] geni_i2c c80000.i2c: Using GPI DMA mode for I2C
> [    0.500155] geni_i2c c80000.i2c: Geni-I2C adaptor successfully added

This does not look correct. In absence of dmas property, the channel
allocation should not have gone ahead and you should not see " Grabbed
GPI dma channels" message!

Btw what is the output of below when dmas was commented out:
cat /sys/kernel/debug/dmaengine/summary

This would show the channels allocated to each controller

-- 
~Vinod