From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cyril Chemparathy Subject: [PATCH 6/9] net: davinci_mdio: use calculated bus access times Date: Mon, 13 Sep 2010 14:07:28 -0400 Message-ID: <1284401251-8846-7-git-send-email-cyril@ti.com> References: <1284401251-8846-1-git-send-email-cyril@ti.com> Cc: michael.williamson@criticallink.com, caglarakyuz@gmail.com, bparrot@ti.com, Cyril Chemparathy To: netdev@vger.kernel.org, davinci-linux-open-source@linux.davincidsp.com, linux-omap@vger.kernel.org Return-path: In-Reply-To: <1284401251-8846-1-git-send-email-cyril@ti.com> Sender: linux-omap-owner@vger.kernel.org List-Id: netdev.vger.kernel.org This patch replaces the hardcoded scan delay with a calculated delay that adjusts to clock rates. This delay is calculated on the basis of a worst case bus transaction time, with generous built-in margins of error. Signed-off-by: Cyril Chemparathy Signed-off-by: Michael Williamson Signed-off-by: Caglar Akyuz --- drivers/net/davinci_mdio.c | 33 +++++++++++++++++++++++---------- 1 files changed, 23 insertions(+), 10 deletions(-) diff --git a/drivers/net/davinci_mdio.c b/drivers/net/davinci_mdio.c index a9fbc26..f2d7639 100644 --- a/drivers/net/davinci_mdio.c +++ b/drivers/net/davinci_mdio.c @@ -83,11 +83,12 @@ struct davinci_mdio_data { struct device *dev; struct mii_bus *bus; bool suspended; + unsigned long access_time; /* jiffies */ }; static void __davinci_mdio_reset(struct davinci_mdio_data *data) { - u32 mdio_in, div; + u32 mdio_in, div, mdio_out_khz, access_time; mdio_in = clk_get_rate(data->clk); div = (mdio_in / data->pdata.bus_freq) - 1; @@ -96,6 +97,25 @@ static void __davinci_mdio_reset(struct davinci_mdio_data *data) /* set enable and clock divider */ __raw_writel(div | CONTROL_ENABLE, &data->regs->control); + + /* + * One mdio transaction consists of: + * 32 bits of preamble + * 32 bits of transferred data + * 24 bits of bus yield (not needed unless shared?) + */ + mdio_out_khz = mdio_in / (1000 * (div + 1)); + access_time = (88 * 1000) / mdio_out_khz; + + /* + * In the worst case, we could be kicking off a user-access immediately + * after the mdio bus scan state-machine triggered its own read. If + * so, our request could get deferred by one access cycle. We + * defensively allow for 4 access cycles. + */ + data->access_time = usecs_to_jiffies(access_time * 4); + if (!data->access_time) + data->access_time = 1; } static int davinci_mdio_reset(struct mii_bus *bus) @@ -105,15 +125,8 @@ static int davinci_mdio_reset(struct mii_bus *bus) __davinci_mdio_reset(data); - /* - * wait for scan logic to settle: - * the scan time consists of (a) a large fixed component, and (b) a - * small component that varies with the mii bus frequency. These - * were estimated using measurements at 1.1 and 2.2 MHz on tnetv107x - * silicon. Since the effect of (b) was found to be largely - * negligible, we keep things simple here. - */ - mdelay(1); + /* wait for scan logic to settle */ + msleep(PHY_MAX_ADDR * data->access_time); /* dump hardware version info */ ver = __raw_readl(&data->regs->version); -- 1.7.0.4