From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gerhard Sittig Subject: [PATCH v1 14/24] powerpc/mpc512x: improve DIU related clock setup Date: Mon, 15 Jul 2013 20:47:43 +0200 Message-ID: <1373914074-20889-15-git-send-email-gsi@denx.de> References: <1373914074-20889-1-git-send-email-gsi@denx.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1373914074-20889-1-git-send-email-gsi-ynQEQJNshbs@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" To: linuxppc-dev-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, Anatolij Gustschin , Mike Turquette , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Cc: Detlev Zundel , Wolfram Sang , Greg Kroah-Hartman , Rob Herring , Mark Brown , Marc Kleine-Budde , David Woodhouse , Wolfgang Grandegger , Mauro Carvalho Chehab List-Id: devicetree@vger.kernel.org adapt the DIU clock initialization to the COMMON_CLK approach: device tree based clock lookup, prepare and unprepare for clocks, work with frequencies not dividers, call the appropriate clk_*() routines and don't access CCM registers, remove the pre-enable workaround in the platform's clock driver the "best clock" determination now completely relies on the platform's clock driver to pick a frequency close to what the caller requests, and merely checks whether the desired frequency was met (is acceptable since it meets the tolerance of the monitor) -- this approach shall succeed upon first try in the usual case, will test a few less desirable yet acceptable frequencies in edge cases, and will fallback to "best effort" if none of the previously tried frequencies pass the test Signed-off-by: Gerhard Sittig --- arch/powerpc/platforms/512x/clock-commonclk.c | 1 - arch/powerpc/platforms/512x/mpc512x_shared.c | 165 +++++++++++++------------ 2 files changed, 88 insertions(+), 78 deletions(-) diff --git a/arch/powerpc/platforms/512x/clock-commonclk.c b/arch/powerpc/platforms/512x/clock-commonclk.c index 218f55b..f31f895 100644 --- a/arch/powerpc/platforms/512x/clock-commonclk.c +++ b/arch/powerpc/platforms/512x/clock-commonclk.c @@ -705,7 +705,6 @@ static void mpc512x_clk_setup_clock_tree(int busfreq) /* some are not yet acquired by their respective drivers */ clk_prepare_enable(clks[MPC512x_CLK_PSC3_MCLK]);/* serial console */ clk_prepare_enable(clks[MPC512x_CLK_FEC]); /* network, NFS */ - clk_prepare_enable(clks[MPC512x_CLK_DIU]); /* display */ clk_prepare_enable(clks[MPC512x_CLK_I2C]); /* * some have their individual clock subtree with separate clock diff --git a/arch/powerpc/platforms/512x/mpc512x_shared.c b/arch/powerpc/platforms/512x/mpc512x_shared.c index a82a41b..3381eea 100644 --- a/arch/powerpc/platforms/512x/mpc512x_shared.c +++ b/arch/powerpc/platforms/512x/mpc512x_shared.c @@ -12,6 +12,7 @@ * (at your option) any later version. */ +#include #include #include #include @@ -70,98 +71,108 @@ struct fsl_diu_shared_fb { bool in_use; }; -#define DIU_DIV_MASK 0x000000ff +/* receives a pixel clock spec in pico seconds, adjusts the DIU clock rate */ void mpc512x_set_pixel_clock(unsigned int pixclock) { - unsigned long bestval, bestfreq, speed, busfreq; - unsigned long minpixclock, maxpixclock, pixval; - struct mpc512x_ccm __iomem *ccm; struct device_node *np; - u32 temp; - long err; - int i; + struct clk *clk_diu; + unsigned long epsilon, minpixclock, maxpixclock; + unsigned long offset, want, got, delta; - np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-clock"); + /* lookup and enable the DIU clock */ + np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-diu"); if (!np) { - pr_err("Can't find clock control module.\n"); + pr_err("Could not find DIU device tree node.\n"); return; } - - ccm = of_iomap(np, 0); + clk_diu = of_clk_get_by_name(np, "per"); of_node_put(np); - if (!ccm) { - pr_err("Can't map clock control module reg.\n"); + if (IS_ERR(clk_diu)) { + pr_err("Could not lookup DIU clock.\n"); return; } - - np = of_find_node_by_type(NULL, "cpu"); - if (np) { - const unsigned int *prop = - of_get_property(np, "bus-frequency", NULL); - - of_node_put(np); - if (prop) { - busfreq = *prop; - } else { - pr_err("Can't get bus-frequency property\n"); - return; - } - } else { - pr_err("Can't find 'cpu' node.\n"); + if (clk_prepare_enable(clk_diu)) { + pr_err("Could not enable DIU clock.\n"); return; } - /* Pixel Clock configuration */ - pr_debug("DIU: Bus Frequency = %lu\n", busfreq); - speed = busfreq * 4; /* DIU_DIV ratio is 4 * CSB_CLK / DIU_CLK */ - - /* Calculate the pixel clock with the smallest error */ - /* calculate the following in steps to avoid overflow */ - pr_debug("DIU pixclock in ps - %d\n", pixclock); - temp = (1000000000 / pixclock) * 1000; - pixclock = temp; - pr_debug("DIU pixclock freq - %u\n", pixclock); - - temp = temp / 20; /* pixclock * 0.05 */ - pr_debug("deviation = %d\n", temp); - minpixclock = pixclock - temp; - maxpixclock = pixclock + temp; - pr_debug("DIU minpixclock - %lu\n", minpixclock); - pr_debug("DIU maxpixclock - %lu\n", maxpixclock); - pixval = speed/pixclock; - pr_debug("DIU pixval = %lu\n", pixval); - - err = LONG_MAX; - bestval = pixval; - pr_debug("DIU bestval = %lu\n", bestval); - - bestfreq = 0; - for (i = -1; i <= 1; i++) { - temp = speed / (pixval+i); - pr_debug("DIU test pixval i=%d, pixval=%lu, temp freq. = %u\n", - i, pixval, temp); - if ((temp < minpixclock) || (temp > maxpixclock)) - pr_debug("DIU exceeds monitor range (%lu to %lu)\n", - minpixclock, maxpixclock); - else if (abs(temp - pixclock) < err) { - pr_debug("Entered the else if block %d\n", i); - err = abs(temp - pixclock); - bestval = pixval + i; - bestfreq = temp; - } + /* + * convert the picoseconds spec into the desired clock rate, + * determine the acceptable clock range for the monitor (+/- 5%), + * do the calculation in steps to avoid integer overflow + */ + pr_debug("DIU pixclock in ps - %u\n", pixclock); + pixclock = (1000000000 / pixclock) * 1000; + pr_debug("DIU pixclock freq - %u\n", pixclock); + epsilon = pixclock / 20; /* pixclock * 0.05 */ + pr_debug("DIU deviation - %lu\n", epsilon); + minpixclock = pixclock - epsilon; + maxpixclock = pixclock + epsilon; + pr_debug("DIU minpixclock - %lu\n", minpixclock); + pr_debug("DIU maxpixclock - %lu\n", maxpixclock); + + /* + * check whether the DIU supports the desired pixel clock + * + * - simply request the desired clock and see what the + * platform's clock driver will make of it, assuming that it + * will setup the best approximation of the requested value + * - try other candidate frequencies in the order of decreasing + * preference (i.e. with increasing distance from the desired + * pixel clock, and checking the lower frequency before the + * higher frequency to not overload the hardware) until the + * first match is found -- any potential subsequent match + * would only be as good as the former match or typically + * would be less preferrable + * + * the offset increment of pixelclock divided by 64 is an + * arbitrary choice -- it's simple to calculate, in the typical + * case we expect the first check to succeed already, in the + * worst case seven frequencies get tested (the exact center and + * three more values each to the left and to the right) before + * the 5% tolerance window is exceeded, resulting in fast enough + * execution yet high enough probability of finding a suitable + * value, while the error rate will be in the order of single + * percents + */ + for (offset = 0; offset <= epsilon; offset += pixclock / 64) { + want = pixclock - offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; + if (!offset) + continue; + want = pixclock + offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; } + if (offset <= epsilon) { + pr_debug("DIU clock accepted - %lu\n", want); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); + return; + } + pr_warn("DIU pixclock auto search unsuccessful\n"); - pr_debug("DIU chose = %lx\n", bestval); - pr_debug("DIU error = %ld\n NomPixClk ", err); - pr_debug("DIU: Best Freq = %lx\n", bestfreq); - /* Modify DIU_DIV in CCM SCFR1 */ - temp = in_be32(&ccm->scfr1); - pr_debug("DIU: Current value of SCFR1: 0x%08x\n", temp); - temp &= ~DIU_DIV_MASK; - temp |= (bestval & DIU_DIV_MASK); - out_be32(&ccm->scfr1, temp); - pr_debug("DIU: Modified value of SCFR1: 0x%08x\n", temp); - iounmap(ccm); + /* + * what is the most appropriate action to take when the search + * for an available pixel clock which is acceptable to the + * monitor has failed? disable the DIU (clock) or just provide + * a "best effort"? we go with the latter + */ + pr_warn("DIU pixclock best effort fallback (backend's choice)\n"); + clk_set_rate(clk_diu, pixclock); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); } enum fsl_diu_monitor_port -- 1.7.10.4 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Gerhard Sittig To: linuxppc-dev@lists.ozlabs.org, Anatolij Gustschin , Mike Turquette , linux-arm-kernel@lists.infradead.org, devicetree-discuss@lists.ozlabs.org Subject: [PATCH v1 14/24] powerpc/mpc512x: improve DIU related clock setup Date: Mon, 15 Jul 2013 20:47:43 +0200 Message-Id: <1373914074-20889-15-git-send-email-gsi@denx.de> In-Reply-To: <1373914074-20889-1-git-send-email-gsi@denx.de> References: <1373914074-20889-1-git-send-email-gsi@denx.de> Cc: Detlev Zundel , Wolfram Sang , Greg Kroah-Hartman , Gerhard Sittig , Rob Herring , Mark Brown , Marc Kleine-Budde , David Woodhouse , Wolfgang Grandegger , Mauro Carvalho Chehab List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , adapt the DIU clock initialization to the COMMON_CLK approach: device tree based clock lookup, prepare and unprepare for clocks, work with frequencies not dividers, call the appropriate clk_*() routines and don't access CCM registers, remove the pre-enable workaround in the platform's clock driver the "best clock" determination now completely relies on the platform's clock driver to pick a frequency close to what the caller requests, and merely checks whether the desired frequency was met (is acceptable since it meets the tolerance of the monitor) -- this approach shall succeed upon first try in the usual case, will test a few less desirable yet acceptable frequencies in edge cases, and will fallback to "best effort" if none of the previously tried frequencies pass the test Signed-off-by: Gerhard Sittig --- arch/powerpc/platforms/512x/clock-commonclk.c | 1 - arch/powerpc/platforms/512x/mpc512x_shared.c | 165 +++++++++++++------------ 2 files changed, 88 insertions(+), 78 deletions(-) diff --git a/arch/powerpc/platforms/512x/clock-commonclk.c b/arch/powerpc/platforms/512x/clock-commonclk.c index 218f55b..f31f895 100644 --- a/arch/powerpc/platforms/512x/clock-commonclk.c +++ b/arch/powerpc/platforms/512x/clock-commonclk.c @@ -705,7 +705,6 @@ static void mpc512x_clk_setup_clock_tree(int busfreq) /* some are not yet acquired by their respective drivers */ clk_prepare_enable(clks[MPC512x_CLK_PSC3_MCLK]);/* serial console */ clk_prepare_enable(clks[MPC512x_CLK_FEC]); /* network, NFS */ - clk_prepare_enable(clks[MPC512x_CLK_DIU]); /* display */ clk_prepare_enable(clks[MPC512x_CLK_I2C]); /* * some have their individual clock subtree with separate clock diff --git a/arch/powerpc/platforms/512x/mpc512x_shared.c b/arch/powerpc/platforms/512x/mpc512x_shared.c index a82a41b..3381eea 100644 --- a/arch/powerpc/platforms/512x/mpc512x_shared.c +++ b/arch/powerpc/platforms/512x/mpc512x_shared.c @@ -12,6 +12,7 @@ * (at your option) any later version. */ +#include #include #include #include @@ -70,98 +71,108 @@ struct fsl_diu_shared_fb { bool in_use; }; -#define DIU_DIV_MASK 0x000000ff +/* receives a pixel clock spec in pico seconds, adjusts the DIU clock rate */ void mpc512x_set_pixel_clock(unsigned int pixclock) { - unsigned long bestval, bestfreq, speed, busfreq; - unsigned long minpixclock, maxpixclock, pixval; - struct mpc512x_ccm __iomem *ccm; struct device_node *np; - u32 temp; - long err; - int i; + struct clk *clk_diu; + unsigned long epsilon, minpixclock, maxpixclock; + unsigned long offset, want, got, delta; - np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-clock"); + /* lookup and enable the DIU clock */ + np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-diu"); if (!np) { - pr_err("Can't find clock control module.\n"); + pr_err("Could not find DIU device tree node.\n"); return; } - - ccm = of_iomap(np, 0); + clk_diu = of_clk_get_by_name(np, "per"); of_node_put(np); - if (!ccm) { - pr_err("Can't map clock control module reg.\n"); + if (IS_ERR(clk_diu)) { + pr_err("Could not lookup DIU clock.\n"); return; } - - np = of_find_node_by_type(NULL, "cpu"); - if (np) { - const unsigned int *prop = - of_get_property(np, "bus-frequency", NULL); - - of_node_put(np); - if (prop) { - busfreq = *prop; - } else { - pr_err("Can't get bus-frequency property\n"); - return; - } - } else { - pr_err("Can't find 'cpu' node.\n"); + if (clk_prepare_enable(clk_diu)) { + pr_err("Could not enable DIU clock.\n"); return; } - /* Pixel Clock configuration */ - pr_debug("DIU: Bus Frequency = %lu\n", busfreq); - speed = busfreq * 4; /* DIU_DIV ratio is 4 * CSB_CLK / DIU_CLK */ - - /* Calculate the pixel clock with the smallest error */ - /* calculate the following in steps to avoid overflow */ - pr_debug("DIU pixclock in ps - %d\n", pixclock); - temp = (1000000000 / pixclock) * 1000; - pixclock = temp; - pr_debug("DIU pixclock freq - %u\n", pixclock); - - temp = temp / 20; /* pixclock * 0.05 */ - pr_debug("deviation = %d\n", temp); - minpixclock = pixclock - temp; - maxpixclock = pixclock + temp; - pr_debug("DIU minpixclock - %lu\n", minpixclock); - pr_debug("DIU maxpixclock - %lu\n", maxpixclock); - pixval = speed/pixclock; - pr_debug("DIU pixval = %lu\n", pixval); - - err = LONG_MAX; - bestval = pixval; - pr_debug("DIU bestval = %lu\n", bestval); - - bestfreq = 0; - for (i = -1; i <= 1; i++) { - temp = speed / (pixval+i); - pr_debug("DIU test pixval i=%d, pixval=%lu, temp freq. = %u\n", - i, pixval, temp); - if ((temp < minpixclock) || (temp > maxpixclock)) - pr_debug("DIU exceeds monitor range (%lu to %lu)\n", - minpixclock, maxpixclock); - else if (abs(temp - pixclock) < err) { - pr_debug("Entered the else if block %d\n", i); - err = abs(temp - pixclock); - bestval = pixval + i; - bestfreq = temp; - } + /* + * convert the picoseconds spec into the desired clock rate, + * determine the acceptable clock range for the monitor (+/- 5%), + * do the calculation in steps to avoid integer overflow + */ + pr_debug("DIU pixclock in ps - %u\n", pixclock); + pixclock = (1000000000 / pixclock) * 1000; + pr_debug("DIU pixclock freq - %u\n", pixclock); + epsilon = pixclock / 20; /* pixclock * 0.05 */ + pr_debug("DIU deviation - %lu\n", epsilon); + minpixclock = pixclock - epsilon; + maxpixclock = pixclock + epsilon; + pr_debug("DIU minpixclock - %lu\n", minpixclock); + pr_debug("DIU maxpixclock - %lu\n", maxpixclock); + + /* + * check whether the DIU supports the desired pixel clock + * + * - simply request the desired clock and see what the + * platform's clock driver will make of it, assuming that it + * will setup the best approximation of the requested value + * - try other candidate frequencies in the order of decreasing + * preference (i.e. with increasing distance from the desired + * pixel clock, and checking the lower frequency before the + * higher frequency to not overload the hardware) until the + * first match is found -- any potential subsequent match + * would only be as good as the former match or typically + * would be less preferrable + * + * the offset increment of pixelclock divided by 64 is an + * arbitrary choice -- it's simple to calculate, in the typical + * case we expect the first check to succeed already, in the + * worst case seven frequencies get tested (the exact center and + * three more values each to the left and to the right) before + * the 5% tolerance window is exceeded, resulting in fast enough + * execution yet high enough probability of finding a suitable + * value, while the error rate will be in the order of single + * percents + */ + for (offset = 0; offset <= epsilon; offset += pixclock / 64) { + want = pixclock - offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; + if (!offset) + continue; + want = pixclock + offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; } + if (offset <= epsilon) { + pr_debug("DIU clock accepted - %lu\n", want); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); + return; + } + pr_warn("DIU pixclock auto search unsuccessful\n"); - pr_debug("DIU chose = %lx\n", bestval); - pr_debug("DIU error = %ld\n NomPixClk ", err); - pr_debug("DIU: Best Freq = %lx\n", bestfreq); - /* Modify DIU_DIV in CCM SCFR1 */ - temp = in_be32(&ccm->scfr1); - pr_debug("DIU: Current value of SCFR1: 0x%08x\n", temp); - temp &= ~DIU_DIV_MASK; - temp |= (bestval & DIU_DIV_MASK); - out_be32(&ccm->scfr1, temp); - pr_debug("DIU: Modified value of SCFR1: 0x%08x\n", temp); - iounmap(ccm); + /* + * what is the most appropriate action to take when the search + * for an available pixel clock which is acceptable to the + * monitor has failed? disable the DIU (clock) or just provide + * a "best effort"? we go with the latter + */ + pr_warn("DIU pixclock best effort fallback (backend's choice)\n"); + clk_set_rate(clk_diu, pixclock); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); } enum fsl_diu_monitor_port -- 1.7.10.4 From mboxrd@z Thu Jan 1 00:00:00 1970 From: gsi@denx.de (Gerhard Sittig) Date: Mon, 15 Jul 2013 20:47:43 +0200 Subject: [PATCH v1 14/24] powerpc/mpc512x: improve DIU related clock setup In-Reply-To: <1373914074-20889-1-git-send-email-gsi@denx.de> References: <1373914074-20889-1-git-send-email-gsi@denx.de> Message-ID: <1373914074-20889-15-git-send-email-gsi@denx.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org adapt the DIU clock initialization to the COMMON_CLK approach: device tree based clock lookup, prepare and unprepare for clocks, work with frequencies not dividers, call the appropriate clk_*() routines and don't access CCM registers, remove the pre-enable workaround in the platform's clock driver the "best clock" determination now completely relies on the platform's clock driver to pick a frequency close to what the caller requests, and merely checks whether the desired frequency was met (is acceptable since it meets the tolerance of the monitor) -- this approach shall succeed upon first try in the usual case, will test a few less desirable yet acceptable frequencies in edge cases, and will fallback to "best effort" if none of the previously tried frequencies pass the test Signed-off-by: Gerhard Sittig --- arch/powerpc/platforms/512x/clock-commonclk.c | 1 - arch/powerpc/platforms/512x/mpc512x_shared.c | 165 +++++++++++++------------ 2 files changed, 88 insertions(+), 78 deletions(-) diff --git a/arch/powerpc/platforms/512x/clock-commonclk.c b/arch/powerpc/platforms/512x/clock-commonclk.c index 218f55b..f31f895 100644 --- a/arch/powerpc/platforms/512x/clock-commonclk.c +++ b/arch/powerpc/platforms/512x/clock-commonclk.c @@ -705,7 +705,6 @@ static void mpc512x_clk_setup_clock_tree(int busfreq) /* some are not yet acquired by their respective drivers */ clk_prepare_enable(clks[MPC512x_CLK_PSC3_MCLK]);/* serial console */ clk_prepare_enable(clks[MPC512x_CLK_FEC]); /* network, NFS */ - clk_prepare_enable(clks[MPC512x_CLK_DIU]); /* display */ clk_prepare_enable(clks[MPC512x_CLK_I2C]); /* * some have their individual clock subtree with separate clock diff --git a/arch/powerpc/platforms/512x/mpc512x_shared.c b/arch/powerpc/platforms/512x/mpc512x_shared.c index a82a41b..3381eea 100644 --- a/arch/powerpc/platforms/512x/mpc512x_shared.c +++ b/arch/powerpc/platforms/512x/mpc512x_shared.c @@ -12,6 +12,7 @@ * (at your option) any later version. */ +#include #include #include #include @@ -70,98 +71,108 @@ struct fsl_diu_shared_fb { bool in_use; }; -#define DIU_DIV_MASK 0x000000ff +/* receives a pixel clock spec in pico seconds, adjusts the DIU clock rate */ void mpc512x_set_pixel_clock(unsigned int pixclock) { - unsigned long bestval, bestfreq, speed, busfreq; - unsigned long minpixclock, maxpixclock, pixval; - struct mpc512x_ccm __iomem *ccm; struct device_node *np; - u32 temp; - long err; - int i; + struct clk *clk_diu; + unsigned long epsilon, minpixclock, maxpixclock; + unsigned long offset, want, got, delta; - np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-clock"); + /* lookup and enable the DIU clock */ + np = of_find_compatible_node(NULL, NULL, "fsl,mpc5121-diu"); if (!np) { - pr_err("Can't find clock control module.\n"); + pr_err("Could not find DIU device tree node.\n"); return; } - - ccm = of_iomap(np, 0); + clk_diu = of_clk_get_by_name(np, "per"); of_node_put(np); - if (!ccm) { - pr_err("Can't map clock control module reg.\n"); + if (IS_ERR(clk_diu)) { + pr_err("Could not lookup DIU clock.\n"); return; } - - np = of_find_node_by_type(NULL, "cpu"); - if (np) { - const unsigned int *prop = - of_get_property(np, "bus-frequency", NULL); - - of_node_put(np); - if (prop) { - busfreq = *prop; - } else { - pr_err("Can't get bus-frequency property\n"); - return; - } - } else { - pr_err("Can't find 'cpu' node.\n"); + if (clk_prepare_enable(clk_diu)) { + pr_err("Could not enable DIU clock.\n"); return; } - /* Pixel Clock configuration */ - pr_debug("DIU: Bus Frequency = %lu\n", busfreq); - speed = busfreq * 4; /* DIU_DIV ratio is 4 * CSB_CLK / DIU_CLK */ - - /* Calculate the pixel clock with the smallest error */ - /* calculate the following in steps to avoid overflow */ - pr_debug("DIU pixclock in ps - %d\n", pixclock); - temp = (1000000000 / pixclock) * 1000; - pixclock = temp; - pr_debug("DIU pixclock freq - %u\n", pixclock); - - temp = temp / 20; /* pixclock * 0.05 */ - pr_debug("deviation = %d\n", temp); - minpixclock = pixclock - temp; - maxpixclock = pixclock + temp; - pr_debug("DIU minpixclock - %lu\n", minpixclock); - pr_debug("DIU maxpixclock - %lu\n", maxpixclock); - pixval = speed/pixclock; - pr_debug("DIU pixval = %lu\n", pixval); - - err = LONG_MAX; - bestval = pixval; - pr_debug("DIU bestval = %lu\n", bestval); - - bestfreq = 0; - for (i = -1; i <= 1; i++) { - temp = speed / (pixval+i); - pr_debug("DIU test pixval i=%d, pixval=%lu, temp freq. = %u\n", - i, pixval, temp); - if ((temp < minpixclock) || (temp > maxpixclock)) - pr_debug("DIU exceeds monitor range (%lu to %lu)\n", - minpixclock, maxpixclock); - else if (abs(temp - pixclock) < err) { - pr_debug("Entered the else if block %d\n", i); - err = abs(temp - pixclock); - bestval = pixval + i; - bestfreq = temp; - } + /* + * convert the picoseconds spec into the desired clock rate, + * determine the acceptable clock range for the monitor (+/- 5%), + * do the calculation in steps to avoid integer overflow + */ + pr_debug("DIU pixclock in ps - %u\n", pixclock); + pixclock = (1000000000 / pixclock) * 1000; + pr_debug("DIU pixclock freq - %u\n", pixclock); + epsilon = pixclock / 20; /* pixclock * 0.05 */ + pr_debug("DIU deviation - %lu\n", epsilon); + minpixclock = pixclock - epsilon; + maxpixclock = pixclock + epsilon; + pr_debug("DIU minpixclock - %lu\n", minpixclock); + pr_debug("DIU maxpixclock - %lu\n", maxpixclock); + + /* + * check whether the DIU supports the desired pixel clock + * + * - simply request the desired clock and see what the + * platform's clock driver will make of it, assuming that it + * will setup the best approximation of the requested value + * - try other candidate frequencies in the order of decreasing + * preference (i.e. with increasing distance from the desired + * pixel clock, and checking the lower frequency before the + * higher frequency to not overload the hardware) until the + * first match is found -- any potential subsequent match + * would only be as good as the former match or typically + * would be less preferrable + * + * the offset increment of pixelclock divided by 64 is an + * arbitrary choice -- it's simple to calculate, in the typical + * case we expect the first check to succeed already, in the + * worst case seven frequencies get tested (the exact center and + * three more values each to the left and to the right) before + * the 5% tolerance window is exceeded, resulting in fast enough + * execution yet high enough probability of finding a suitable + * value, while the error rate will be in the order of single + * percents + */ + for (offset = 0; offset <= epsilon; offset += pixclock / 64) { + want = pixclock - offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; + if (!offset) + continue; + want = pixclock + offset; + pr_debug("DIU checking clock - %lu\n", want); + clk_set_rate(clk_diu, want); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + if (delta < epsilon) + break; } + if (offset <= epsilon) { + pr_debug("DIU clock accepted - %lu\n", want); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); + return; + } + pr_warn("DIU pixclock auto search unsuccessful\n"); - pr_debug("DIU chose = %lx\n", bestval); - pr_debug("DIU error = %ld\n NomPixClk ", err); - pr_debug("DIU: Best Freq = %lx\n", bestfreq); - /* Modify DIU_DIV in CCM SCFR1 */ - temp = in_be32(&ccm->scfr1); - pr_debug("DIU: Current value of SCFR1: 0x%08x\n", temp); - temp &= ~DIU_DIV_MASK; - temp |= (bestval & DIU_DIV_MASK); - out_be32(&ccm->scfr1, temp); - pr_debug("DIU: Modified value of SCFR1: 0x%08x\n", temp); - iounmap(ccm); + /* + * what is the most appropriate action to take when the search + * for an available pixel clock which is acceptable to the + * monitor has failed? disable the DIU (clock) or just provide + * a "best effort"? we go with the latter + */ + pr_warn("DIU pixclock best effort fallback (backend's choice)\n"); + clk_set_rate(clk_diu, pixclock); + got = clk_get_rate(clk_diu); + delta = abs(pixclock - got); + pr_debug("DIU pixclock want %u, got %lu, delta %lu, eps %lu\n", + pixclock, got, delta, epsilon); } enum fsl_diu_monitor_port -- 1.7.10.4