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Date:   Wed, 14 Nov 2018 09:06:31 +1100
From:   James Cameron <quozl@laptop.org>
To:     Lubomir Rintel <lkundrak@v3.sk>
Cc:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Darren Hart <dvhart@infradead.org>,
        Andy Shevchenko <andy@infradead.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Sebastian Reichel <sre@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Eric Miao <eric.y.miao@gmail.com>,
        Haojian Zhuang <haojian.zhuang@gmail.com>,
        Daniel Mack <daniel@zonque.org>,
        Robert Jarzmik <robert.jarzmik@free.fr>,
        linux-spi <linux-spi@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        Platform Driver <platform-driver-x86@vger.kernel.org>,
        devel@driverdev.osuosl.org, Linux PM <linux-pm@vger.kernel.org>
Subject: Re: [PATCH 06/15] Platform: OLPC: Add XO-1.75 EC driver
Message-ID: <20181113220631.GB22127@us.netrek.org>
References: <20181010172300.317643-1-lkundrak@v3.sk>
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On Tue, Nov 13, 2018 at 06:26:09PM +0100, Lubomir Rintel wrote:
> Hi,
> 
> first of all -- thanks for such a careful review. It is very helpful.
> 
> Wherever I don't respond to you, I'm just following what you wrote. It
> would perhaps be tiresome to respond to "Yes, will fix in next version"
> to every single point.
> 
> I'll be following up with a new version in a few days; I'm mostly done
> with this one but I've not finished addressing the followup ones.
> 
> On Fri, 2018-10-19 at 19:06 +0300, Andy Shevchenko wrote:
> > On Wed, Oct 10, 2018 at 8:24 PM Lubomir Rintel <lkundrak@v3.sk>
> > wrote:
> > > It's based off the driver from the OLPC kernel sources. Somewhat
> > > modernized and cleaned up, for better or worse.
> > > 
> > > Modified to plug into the olpc-ec driver infrastructure (so that
> > > battery
> > > interface and debugfs could be reused) and the SPI slave framework.
> > > +#include <asm/system_misc.h>
> > 
> > asm/* goes after linux/*
> > 
> > > +#include <linux/delay.h>
> > > +#include <linux/gpio/consumer.h>
> > > +#include <linux/spinlock.h>
> > > +#include <linux/completion.h>
> > > +#include <linux/slab.h>
> > > +#include <linux/platform_device.h>
> > > +#include <linux/ctype.h>
> > > +#include <linux/olpc-ec.h>
> > > +#include <linux/spi/spi.h>
> > > +#include <linux/reboot.h>
> > > +#include <linux/input.h>
> > > +#include <linux/kfifo.h>
> > > +#include <linux/module.h>
> > > +#include <linux/power_supply.h>
> > 
> > Easy to maintain when it's sorted.
> > 
> > > +       { 0 },
> > 
> > Terminators are better without trailing comma.
> > 
> > > +#define EC_CMD_LEN             8
> > > +#define EC_MAX_RESP_LEN                16
> > > +#define LOG_BUF_SIZE           127
> > 
> > 127 sounds slightly strange. Is it by specification of protocol?
> > Would
> > it be better to define it 128 bytes / items?
> > 
> > > +static int olpc_xo175_ec_is_valid_cmd(u8 cmd)
> > > +{
> > > +       const struct ec_cmd_t *p;
> > > +
> > > +       for (p = olpc_xo175_ec_cmds; p->cmd; p++) {
> > > +               if (p->cmd == cmd)
> > > +                       return p->bytes_returned;
> > > +       }
> > > +
> > > +       return -1;
> > 
> > -EINVAL ?
> > 
> > > +}
> > > +static void olpc_xo175_ec_complete(void *arg);
> > 
> > Hmm... Can we avoid forward declaration?
> 
> I don't think we can.
> 
> > > +       channel = priv->rx_buf[0];
> > > +       byte = priv->rx_buf[1];
> > 
> > Maybe specific structures would fit better?
> > 
> > Like
> > 
> > struct olpc_ec_resp_hdr {
> >  u8 channel;
> >  u8 byte;
> > ...
> > }
> > 
> > > +               dev_warn(dev, "kbd/tpad not supported\n");
> > 
> > Please, spell it fully as touchpad and keyboard.
> > 
> > > +                       pm_wakeup_event(priv->pwrbtn->dev.parent,
> > > 1000);
> > 
> > Magic number.
> > 
> > > +                       /* For now, we just ignore the unknown
> > > events. */
> > 
> > dev_dbg(dev, "Ignored unknown event %.2x\n", byte);
> > 
> > ?
> > 
> > > if (isprint(byte)) {
> > > +                       priv->logbuf[priv->logbuf_len++] = byte;
> > > +                       if (priv->logbuf_len == LOG_BUF_SIZE)
> > > +                               olpc_xo175_ec_flush_logbuf(priv);
> > > +               }
> > 
> > You may consider to take everything and run %pE when printing instead
> > of %s.
> > 
> > > +static int olpc_xo175_ec_cmd(u8 cmd, u8 *inbuf, size_t inlen, u8
> > > *resp,
> > > +                                       size_t resp_len, void
> > > *ec_cb_arg)
> > > +{
> > > +       struct olpc_xo175_ec *priv = ec_cb_arg;
> > > +       struct device *dev = &priv->spi->dev;
> > > +       unsigned long flags;
> > > +       int nr_bytes;
> > > +       int ret = 0;
> > > +
> > > +       dev_dbg(dev, "CMD %x, %d bytes expected\n", cmd, resp_len);
> > > +
> > > +       if (inlen > 5) {
> > 
> > Magic number.
> > 
> > > +               dev_err(dev, "command len %d too big!\n",
> > > resp_len);
> > > +               return -EOVERFLOW;
> > > +       }
> > > +       WARN_ON(priv->suspended);
> > > +       if (priv->suspended)
> > 
> > if (WARN_ON(...)) ?
> > 
> > > +               return -EBUSY;
> > > +       if (resp_len > nr_bytes)
> > > +               resp_len = nr_bytes;
> > 
> > resp_len = min(resp_len, nr_bytes);
> > 
> > > +       priv->cmd[0] = cmd;
> > > +       priv->cmd[1] = inlen;
> > > +       priv->cmd[2] = 0;
> > 
> > Perhaps specific struct header for this?
> > 
> > > +       memset(resp, 0, resp_len);
> > 
> > Wouldn't be better to do this in where actual response has been
> > filled?
> > 
> > > +       if (!wait_for_completion_timeout(&priv->cmd_done,
> > > +                       msecs_to_jiffies(4000))) {
> > 
> > Magic number.
> > 
> > > +       }
> > > +       /* Deal with the results. */
> > 
> > Somehow feels noisy / unneeded comment.
> > 
> > > +       if (priv->cmd_state == CMD_STATE_ERROR_RECEIVED) {
> > > +               /* EC-provided error is in the single response byte
> > > */
> > > +               dev_err(dev, "command 0x%x returned error 0x%x\n",
> > > +                                                       cmd, priv-
> > > >resp[0]);
> > 
> > Indentation.
> > 
> > > +               ret = -EREMOTEIO;
> > > +       } else if (priv->resp_len != nr_bytes) {
> > > +               dev_err(dev, "command 0x%x returned %d bytes,
> > > expected %d bytes\n",
> > > +                                               cmd, priv-
> > > >resp_len, nr_bytes);
> > > +               ret = -ETIMEDOUT;
> > 
> > In the message I see nothing about timeout.
> > 
> > > +       } else {
> > > +       }
> > > +}
> > > +static int olpc_xo175_ec_set_event_mask(unsigned int mask)
> > > +{
> > > +       unsigned char args[2];
> > 
> > u8
> > 
> > > +
> > > +       args[0] = mask & 0xff;
> > > +       args[1] = (mask >> 8) & 0xff;
> > 
> > ...mask >> 0;
> > ...mask >> 8;
> > 
> > > +       return olpc_ec_cmd(CMD_WRITE_EXT_SCI_MASK, args, 2, NULL,
> > > 0);
> > > +}
> > > +
> > > +static void olpc_xo175_ec_restart(enum reboot_mode mode, const
> > > char *cmd)
> > > +{
> > > +       while (1) {
> > > +               olpc_ec_cmd(CMD_POWER_CYCLE, NULL, 0, NULL, 0);
> > > +               mdelay(1000);
> > > +       }
> > > +}
> > > +
> > > +static void olpc_xo175_ec_power_off(void)
> > > +{
> > > +       while (1) {
> > > +               olpc_ec_cmd(CMD_POWER_OFF, NULL, 0, NULL, 0);
> > > +               mdelay(1000);
> > > +       }
> > > +}
> > > +
> > > +#ifdef CONFIG_PM
> > > +static int olpc_xo175_ec_suspend(struct device *dev)
> > 
> > __maybe_unused  instead of ugly #ifdef?
> > 
> > > +{
> > > +       struct platform_device *pdev = to_platform_device(dev);
> > > +       struct olpc_xo175_ec *priv = platform_get_drvdata(pdev);
> > 
> > dev_get_drvdata() or how is it called?
> > 
> > > +       unsigned char hintargs[5];
> > 
> > struct olpc_ec_hint_cmd {
> > u8 ...
> > u32 ...
> > };
> > 
> > ?
> > 
> > > +       static unsigned int suspend_count;
> > 
> > u32 I suppose.
> > 
> > > +
> > > +       suspend_count++;
> > > +       dev_dbg(dev, "%s: suspend sync %08x\n", __func__,
> > > suspend_count);
> > 
> > __func__ can be issued if user asked for via Dynamic Debug interface.
> > 
> > > +       /*
> > > +        * First byte is 1 to indicate suspend, the rest is an
> > > integer
> > > +        * counter.
> > > +        */
> > > +       hintargs[0] = 1;
> > > +       memcpy(&hintargs[1], &suspend_count, 4);
> > > +       olpc_ec_cmd(CMD_SUSPEND_HINT, hintargs, 5, NULL, 0);
> > 
> > What do you need this counter for?
> 
> It doesn't seem to be actually used in the EC; the firmware just
> includes it in its debug log. I'm not sure if all firmware versions
> behave this way and I'd prefer to keep it.

Some firmware versions rely on it, as the SOC_SLEEP line was
unreliable where the board revision is B3 or earlier.

(internal reference: Paul Fox Wed, 10 Oct 2012 09:39:44 -0400)

Although population of B3 and earlier was low, prototypes were given
out to many rather than destroyed.

> 
> I'm adding a comment.
> 
> > 
> > > +       priv->suspended = true;
> > 
> > Hmm... Who is the user of it?
> > 
> > > +       return 0;
> > > +}
> > > +
> > > +static int olpc_xo175_ec_resume_noirq(struct device *dev)
> > > +{
> > > +       struct platform_device *pdev = to_platform_device(dev);
> > > +       struct olpc_xo175_ec *priv = platform_get_drvdata(pdev);
> > > +
> > > +       priv->suspended = false;
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static int olpc_xo175_ec_resume(struct device *dev)
> > > +{
> > > +       struct platform_device *pdev = to_platform_device(dev);
> > > +       struct olpc_xo175_ec *priv = platform_get_drvdata(pdev);
> > > +       unsigned char x = 0;
> > 
> > u8
> > 
> > > +       priv->suspended = false;
> > 
> > Isn't it redundant since noirq callback above?
> > 
> > > +       /*
> > > +        * The resume hint is only needed if no other commands are
> > > +        * being sent during resume. all it does is tell the EC
> > > +        * the SoC is definitely awake.
> > > +        */
> > > +       olpc_ec_cmd(CMD_SUSPEND_HINT, &x, 1, NULL, 0);
> > > +
> > > +       /* Enable all EC events while we're awake */
> > > +       olpc_xo175_ec_set_event_mask(0xffff);
> > 
> > #define EC_ALL_EVENTS GENMASK(15, 0)
> > 
> > > +}
> > > +#endif
> > > +static struct platform_device *olpc_ec;
> > 
> > I would rather see this at the top of file.
> > 
> > > +static int olpc_xo175_ec_probe(struct spi_device *spi)
> > > +{
> > > +       if (olpc_ec) {
> > > +               dev_err(&spi->dev, "OLPC EC already
> > > registered.\n");
> > > +               return -EBUSY;
> > > +       }
> > 
> > It's racy against parallel probe called. I don't think it would be a
> > real issue, just let you know.
> > 
> > 
> > > +       /* Set up power button input device */
> > > +       priv->pwrbtn = devm_input_allocate_device(&spi->dev);
> > > +       if (!priv->pwrbtn)
> > > +               return -ENOMEM;
> > > +       priv->pwrbtn->name = "Power Button";
> > > +       priv->pwrbtn->dev.parent = &spi->dev;
> > > +       input_set_capability(priv->pwrbtn, EV_KEY, KEY_POWER);
> > > +       ret = input_register_device(priv->pwrbtn);
> > > +       if (ret) {
> > > +               dev_err(&spi->dev, "error registering input device:
> > > %d\n", ret);
> > > +               return ret;
> > > +       }
> > 
> > I would split out power button driver, but it's up to you.
> > 
> > 
> > > +       /* Enable all EC events while we're awake */
> > > +       olpc_xo175_ec_set_event_mask(0xffff);
> > 
> > See above about this magic.
> > 
> > > +}
> > > +#ifdef CONFIG_PM
> > > +       .suspend        = olpc_xo175_ec_suspend,
> > > +       .resume_noirq   = olpc_xo175_ec_resume_noirq,
> > > +       .resume         = olpc_xo175_ec_resume,
> > > +#endif
> > 
> > SET_SYSTEM_SLEEP_PM_OPS() ?
> > SET_NOIRQ_SYSTEM_SLEEP_PM_OPS() ?
> > 
> > > +static const struct of_device_id olpc_xo175_ec_of_match[] = {
> > > +       { .compatible = "olpc,xo1.75-ec" },
> > > +       { },
> > 
> > No comma for terminators.
> > 
> > > +};
> 
> Thanks,
> Lubo
> 

-- 
James Cameron
http://quozl.netrek.org/