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Thu, 16 Aug 2018 02:12:13 -0700 (PDT) Date: Thu, 16 Aug 2018 10:12:11 +0100 From: Lee Jones To: Richard Fitzgerald Cc: patches@opensource.cirrus.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mfd: madera: Don't use regmap_read_poll_timeout to poll for BOOT_DONE Message-ID: <20180816091211.GF10054@dell> References: <20180807090813.15695-1-rf@opensource.cirrus.com> <20180807090813.15695-2-rf@opensource.cirrus.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180807090813.15695-2-rf@opensource.cirrus.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 07 Aug 2018, Richard Fitzgerald wrote: > While polling for BOOT_DONE the chip could NAK a read because it is > still booting, which would terminate the regmap_read_poll_timeout() > with an error. > > Instead implement a polling loop that ignores read errors so we > always poll until the chip signals boot or the loop times out. > > Signed-off-by: Richard Fitzgerald > --- > drivers/mfd/madera-core.c | 38 ++++++++++++++++++++++++-------------- > 1 file changed, 24 insertions(+), 14 deletions(-) > > diff --git a/drivers/mfd/madera-core.c b/drivers/mfd/madera-core.c > index 8cfea969b060..bc5545c53ee5 100644 > --- a/drivers/mfd/madera-core.c > +++ b/drivers/mfd/madera-core.c > @@ -132,33 +132,43 @@ const char *madera_name_from_type(enum madera_type type) > } > EXPORT_SYMBOL_GPL(madera_name_from_type); > > -#define MADERA_BOOT_POLL_MAX_INTERVAL_US 5000 > -#define MADERA_BOOT_POLL_TIMEOUT_US 25000 > +#define MADERA_BOOT_POLL_INTERVAL_USEC 5000 > +#define MADERA_BOOT_POLL_TIMEOUT_USEC 25000 > > static int madera_wait_for_boot(struct madera *madera) > { > - unsigned int val; > - int ret; > + ktime_t timeout; > + unsigned int val = 0; > + int ret = 0; > > /* > * We can't use an interrupt as we need to runtime resume to do so, > * so we poll the status bit. This won't race with the interrupt > * handler because it will be blocked on runtime resume. > + * The chip could NAK a read request while it is booting so ignore > + * errors from regmap_read. > */ > - ret = regmap_read_poll_timeout(madera->regmap, > - MADERA_IRQ1_RAW_STATUS_1, > - val, > - (val & MADERA_BOOT_DONE_STS1), > - MADERA_BOOT_POLL_MAX_INTERVAL_US, > - MADERA_BOOT_POLL_TIMEOUT_US); > - > - if (ret) > - dev_err(madera->dev, "Polling BOOT_DONE_STS failed: %d\n", ret); > + regmap_read(madera->regmap, MADERA_IRQ1_RAW_STATUS_1, &val); > + if (val & MADERA_BOOT_DONE_STS1) > + goto done; Move the usleep_range() invokation to after the regmap_read(), then you can remove these 3 lines and have the same semantics. > + timeout = ktime_add_us(ktime_get(), MADERA_BOOT_POLL_TIMEOUT_USEC); > + do { > + usleep_range(MADERA_BOOT_POLL_INTERVAL_USEC / 2, > + MADERA_BOOT_POLL_INTERVAL_USEC); > + regmap_read(madera->regmap, MADERA_IRQ1_RAW_STATUS_1, &val); > + if (val & MADERA_BOOT_DONE_STS1) > + goto done; > + } while (ktime_compare(ktime_get(), timeout) <= 0); > + > + dev_err(madera->dev, "Polling BOOT_DONE_STS timed out\n"); > + ret = -ETIMEDOUT; > > /* > * BOOT_DONE defaults to unmasked on boot so we must ack it. > - * Do this unconditionally to avoid interrupt storms. > + * Do this even after a timeout to avoid interrupt storms. > */ > +done: > regmap_write(madera->regmap, MADERA_IRQ1_STATUS_1, > MADERA_BOOT_DONE_EINT1); > -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog