Date:	Mon, 13 Jul 2015 15:27:29 -0700
From:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
To:	Georgi Djakov <georgi.djakov@...aro.org>
CC:	<bjorn@...o.se>, Kumar Gala <galak@...eaurora.org>,
	Andy Gross <agross@...eaurora.org>,
	David Brown <davidb@...eaurora.org>,
	<linux-kernel@...r.kernel.org>, <linux-soc@...r.kernel.org>,
	Jeffrey Hugo <jhugo@...eaurora.org>,
	<linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v2 04/11] soc: qcom: Add Shared Memory Driver

On Tue 07 Jul 06:45 PDT 2015, Georgi Djakov wrote:

> Hi Bjorn,
> Thank you for this patchset! Some nits and a question below.
> 

Thank you!

> On 06/27/2015 12:50 AM, bjorn@...o.se wrote:
> > From: Bjorn Andersson <bjorn.andersson@...ymobile.com>
> > 
> > This adds the Qualcomm Shared Memory Driver (SMD) providing
> > communication channels to remote processors, ontop of SMEM.
> > 
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@...ymobile.com>
> > ---
> >  drivers/soc/qcom/Kconfig     |    8 +
> >  drivers/soc/qcom/Makefile    |    1 +
> >  drivers/soc/qcom/smd.c       | 1324 ++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/soc/qcom/smd.h |   46 ++
> >  4 files changed, 1379 insertions(+)
> >  create mode 100644 drivers/soc/qcom/smd.c
> >  create mode 100644 include/linux/soc/qcom/smd.h
> > 
> [...]
> > --- /dev/null
> > +++ b/drivers/soc/qcom/smd.c
> > @@ -0,0 +1,1324 @@
> > +/*
> > + * Copyright (c) 2015, Sony Mobile Communications AB.
> > + * Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 and
> > + * only version 2 as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/delay.h>
> 
> unused?
> 

Right, used to just delay on the tx buffer being full, will drop.

> [...]
> > +
> > +#define GET_RX_CHANNEL_INFO(channel, param) \
> > +	(channel->rx_info_word ? \
> > +		channel->rx_info_word->param : \
> > +		channel->rx_info->param)
> > +
> > +#define SET_RX_CHANNEL_INFO(channel, param, value) \
> > +	(channel->rx_info_word ? \
> > +		(channel->rx_info_word->param = value) : \
> > +		(channel->rx_info->param = value))
> > +
> > +#define GET_TX_CHANNEL_INFO(channel, param) \
> > +	(channel->rx_info_word ? \
> 
> Maybe this should be tx_info_word?
> 

There's no practical difference, but I'll update it.

> > +		channel->tx_info_word->param : \
> > +		channel->tx_info->param)
> > +
> > +#define SET_TX_CHANNEL_INFO(channel, param, value) \
> > +	(channel->rx_info_word ? \
> 
> ditto?
> 

ditto...

> > +		(channel->tx_info_word->param = value) : \
> > +		(channel->tx_info->param = value))
> > +
> [...]
> > +	ret = qcom_smem_get(edge->edge_id, smem_fifo_item, &fifo_base, &fifo_size);
> > +	if (ret)
> > +		goto free_name_and_channel;
> > +
> > +	/* The channel consist of a rx and tx fifo of equal size */
> > +	fifo_size /= 2;
> > +
> > +	dev_dbg(smd->dev, "new channel '%s' info-size: %d fifo-size: %zu\n",
> 
> %zu for info-size?
> 

Hmm, the compiler only complained about the fifo_size, but you're of
course right.

> > +			  name, info_size, fifo_size);
> > +
> 
> [...]
> > +static int __init qcom_smd_init(void)
> > +{
> > +	int ret;
> > +
> > +	ret = bus_register(&qcom_smd_bus);
> > +	if (ret) {
> > +		pr_err("failed to register smd bus: %d\n", ret);
> > +		return ret;
> > +	}
> > +
> > +	return platform_driver_register(&qcom_smd_driver);
> > +}
> > +arch_initcall(qcom_smd_init);
> > +
> > +static void __exit qcom_smd_exit(void)
> > +{
> > +	platform_driver_unregister(&qcom_smd_driver);
> > +	bus_unregister(&qcom_smd_bus);
> > +}
> > +module_exit(qcom_smd_exit);
> > +
> [...]
> > +/**
> > + * struct qcom_smd_driver - smd driver struct
> > + * @driver:	underlying device driver
> > + * @probe:	invoked when the smd channel is found
> > + * @remove:	invoked when the smd channel is closed
> > + * @callback:	invoked when an inbound message is received on the channel,
> > + *		should return 0 on success or -EBUSY if the data cannot be
> > + *		consumed at this time
> > + */
> > +struct qcom_smd_driver {
> > +	struct device_driver driver;
> > +	int (*probe)(struct qcom_smd_device *dev);
> > +	void (*remove)(struct qcom_smd_device *dev);
> > +	int (*callback)(struct qcom_smd_device *, const void *, size_t);
> > +};
> > +
> > +int qcom_smd_driver_register(struct qcom_smd_driver *drv);
> > +void qcom_smd_driver_unregister(struct qcom_smd_driver *drv);
> > +
> > +#define module_qcom_smd_driver(__smd_driver) \
> > +	module_driver(__smd_driver, qcom_smd_driver_register, \
> > +		      qcom_smd_driver_unregister)
> > +
> 
> This comment is mostly related to your RPM over SMD driver patch, as
> i have a RPM clock driver based on it. The RPM clock driver registers
> some fundamental stuff like XO and i had to hack smd-rpm to probe
> earlier, so that most other drivers can initialize. So i was wondering,
> what if we register the drivers on the bus earlier? What do you think?
> 

My only concern would be that if we're calling
qcom_smd_driver_register() before the smd arch_initcall has registered
the bus it will fail.

Part of this I see no problem with modifying the rpm driver to register
earlier - and it would be good to have those regulators earlier as
well...


I've intentionally not done anything about this, because it's helped to
smoke out a bunch of EPROBE_DEFER issues for me already, but longer term
it's not okay for all our drivers to fail 2-3 times before the
regulators are up...

Regards,
Bjorn
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