Re: [alsa-devel] [PATCH v2 2/6] ASoC: Davinci: McBSP: add device tree support for McBSP

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On 15.04.2016 11:32, Peter Ujfalusi wrote:
On 04/11/16 14:45, Petr Kulhavy wrote:
This adds DT support for the TI DA8xx/OMAP-L1x/AM17xx/AM18xx McBSP driver.

Signed-off-by: Petr Kulhavy <petr@xxxxxxxxx>
---
v1: initial
v2: remove "-audio" postfix from the compatible string
     of_match_table renamed consistently with the rest of the file (davinci_i2s_match)
     "channel-combine" property removed
     devicetree DMA configuration in probe simplified

  sound/soc/davinci/Kconfig       |   6 ++-
  sound/soc/davinci/davinci-i2s.c | 116 +++++++++++++++++++++++++++++++---------
  2 files changed, 95 insertions(+), 27 deletions(-)

diff --git a/sound/soc/davinci/Kconfig b/sound/soc/davinci/Kconfig
index 50ca291cc225..6b732d8e5896 100644
--- a/sound/soc/davinci/Kconfig
+++ b/sound/soc/davinci/Kconfig
@@ -16,7 +16,11 @@ config SND_EDMA_SOC
  	  - DRA7xx family
config SND_DAVINCI_SOC_I2S
-	tristate
+	tristate "DaVinci Multichannel Buffered Serial Port (McBSP) support"
+	depends on SND_EDMA_SOC
+	help
+	  Say Y or M here if you want to have support for McBSP IP found in
+	  Texas Instruments DaVinci DA850 SoCs.
config SND_DAVINCI_SOC_MCASP
  	tristate "Multichannel Audio Serial Port (McASP) support"
diff --git a/sound/soc/davinci/davinci-i2s.c b/sound/soc/davinci/davinci-i2s.c
index ec98548a5fc9..a3f82d1a73dc 100644
--- a/sound/soc/davinci/davinci-i2s.c
+++ b/sound/soc/davinci/davinci-i2s.c
@@ -4,9 +4,15 @@
   * Author:      Vladimir Barinov, <vbarinov@xxxxxxxxxxxxxxxxx>
   * Copyright:   (C) 2007 MontaVista Software, Inc., <source@xxxxxxxxxx>
   *
+ * DT support	(c) 2016 Petr Kulhavy, Barix AG <petr@xxxxxxxxx>
+ *		based on davinci-mcasp.c DT support
+ *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
+ *
+ * TODO:
+ * on DA850 implement HW FIFOs instead of DMA into DXR and DRR registers
   */
#include <linux/init.h>
@@ -648,15 +654,62 @@ static const struct snd_soc_component_driver davinci_i2s_component = {
  	.name		= "davinci-i2s",
  };
+static struct snd_platform_data*
+davinci_i2s_set_pdata_from_of(struct platform_device *pdev)
It is a bit misleading function name, would be better to name it as
davinci_i2s_get_pdata()

as it will fetch the legacy pdata or craft one when booting with DT.
Thanks, I will change the name.
+
+	/* parse properties here */
+
+	/*
+	 * pdata->clk_input_pin is deliberately not exported to DT
+	 * and the default value of the clk_input_pin is MCBSP_CLKR.
+	 * The value MCBSP_CLKS makes no sense as it turns the CPU
+	 * to a bit clock master in the SND_SOC_DAIFMT_CBM_CFS mode
+	 * where it should be bit clock slave!
+	 */
+
+	return pdata;
+}
+
  static int davinci_i2s_probe(struct platform_device *pdev)
  {
+	struct snd_dmaengine_dai_dma_data *dma_data;
+	struct snd_platform_data *pdata;
  	struct davinci_mcbsp_dev *dev;
  	struct resource *mem, *res;
  	void __iomem *io_base;
  	int *dma;
  	int ret;
- mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	pdata = davinci_i2s_set_pdata_from_of(pdev);
+	if (IS_ERR(pdata)) {
+		dev_err(&pdev->dev, "Error populating platform data, err %ld\n",
+			PTR_ERR(pdata));
+		return PTR_ERR(pdata);
+	}
The current driver does not use the pdata as far as I can see. Kind of
strange. So now in DT boot you will allocate memory for the pdata, which is
not used by the driver at all.
I think we should implement the pdata handling in the driver first for the
legacy mode, then probably having pdata allocated for DT case might make sense.
Indeed the current driver does not use pdata. Neither the legacy board drivers in arch/mach-davinci do. Well, except for the dm365_evm which sets the asp_chan_q which is later not used:

static struct snd_platform_data dm365_evm_snd_data __maybe_unused = {
        .asp_chan_q = EVENTQ_3,
};


If the pdata is not used at all I would completely drop it.
Or what do you think the pdata should carry?

Petr
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